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  • 801.
    Wegner, Robin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Kombinerat system för ventilation och rumsuppvärmning: Parameterundersökning i simuleringsmodell för takvärmesystem2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A large amount of our time is spent indoors in an artificial climate. To make the experience pleasant there are requirements on the ventilation and the heating system. At the present time the most common form of heating is a radiator system complemented with a ventilation system. A ceiling heating system with combined heating and ventilation can replace the two separated systems. The benefit with a ceiling heating solution is that it saves space since the radiator system is no longer needed. This report aim to evaluate if it is possible to replace a radiator system with a ceiling heating system and maintain a pleasant indoor climate. The ceiling heating system is designed as a comfort module that blows air in four directions, the module is placed in the centre of the ceiling and is heating the room with warm air. The aim of this report is to evaluate which parameters that affects the indoor climate and how these are to be set to make the climate most pleasant. A comparison between the energy efficiency of a radiator system and a ceiling heating system is made.

    By using the simulation program COMSOL is it possible to evaluate the ceiling heating system and see how the: the angel of which the air enters the room, area of the module that distribute the air in to the room and the temperature of the air entering the room. The climate is evaluated by a number of key numbers which indicates how many of the individuals that feel discomfort for different module set ups. These numbers are plotted with the temperature and different design on the comfort module. The key numbers that will be used is PPD-value, PD-value, radiation asymmetry on a plane and the temperature difference between ankles and head. To be able to compare the ceiling heating systems energy loss through the façade with the radiator systems energy loss a simulation model with a radiator as heating solution were also created. To be able to verify the simulation a lab was executed under similar conditions.

    The simulations shows that a good indoor climate based on PPD-value is achievable for all different designs of the comfort module with a difference of what temperature that was necessary to achieve PPD=5 %. A problem with the ceiling heating system is that the air does not stir as well as it does when using the radiator system and that the PD-value is too high. There’s a very small difference in energy efficiency between the radiator and ceiling heating system.

  • 802. Welin-Klintström, S.
    et al.
    Lestelius, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science.
    Liedberg, B.
    Tengvall, P.
    Comparison between wettability gradients made on gold and on Si/SiO2 substrates1999In: Colloids and Surfaces B: Biointerfaces, Vol. vol 15, p. 81-87Article in journal (Refereed)
  • 803.
    Wickholm, Kristina
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi.
    Williams, Helén
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Lindström, Annika
    Innventia.
    Lorentzon, Ann
    Innventia.
    Wikström, Fredrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Innovative packaging for reduction of food waste from producer to consumer2016Conference paper (Other academic)
    Abstract [en]

    Increasing population and environmental changes poses a significant pressure on the global food supply chain. With the large quantities of food waste that’s been reported over the past couple of years packaging can play a more significant role in reducing the food wastage. Together with actors along the entire value chain we are developing new innovative packaging solutions to reduce food waste throughout the value chain, from food producers to consumers. The purpose of the study is to design and optimize new packaging system solutions so that no part of the chain is optimized at the expense of any other part. In the fall of 2015 the food wastage was examined in three supply chains, salsa in glass jar (A), rice pudding in plastic packaging (B) and lettuce in plastic packaging (C), by using waste audits in the businesses, collecting, comparing and analyzing data. For consumer insights ethnographic studies was used in ten Swedish households. Interviews have also been conducted with consumers in retail stores. The supply chain study indicates little wastage for A and B and higher for C. Consumer report some handling difficulties with the food packaging and reasons why food is wasted. The main reasons being that the food gets bad, difficulties to empty the packaging and that the amount of food is higher than their needs. A majority of the consumer state that they often view packaging as something unnecessary. Consumers do not give packaging functions many thoughts in general and many have difficulties in judging the packaging functions.

  • 804.
    Wiegandt, Marcus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Småskalig tappvarmvattenuppvärmning med värmepump: Metodval och kondensorutformning för laddning av en befintlig varmvattenberedare2014Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    To reduce the use of electricity in households heated with direct-acting electricity, a heat pump dedicated to heat water has been developed. As a consequence, the power consumption and the cost for heating water are expected to reduce to less than half.

    The water, heated by the heat pump will be filled in a storage water heater and thereby unburden the electric element for the household’s everyday routine. Several alternatives for how the storage water heater will be filled have been developed from the criteria efficiency, economy, simplicity and space occupying and each concept have been graded. The best concept to fill the storage water heater has been elected and is thereafter dimensioned.

    The results show that the best of the proposed ways to fill a storage water heater with warm water from the heat pump is to suck the cold water from the bottom of the storage water heater and heat exchange it in a helically coiled tube-in-tube condenser. When the water is heated to 60°C, to prevent the growth of Legionella bacteria, it gets pumped back to the storage water heater where it’s filled in the top for best stratification. The condensers length is decided to be 7,57 meters. The pressure loss due to the condensation has been calculated but is assumed to not affect the heat transfer. A pump is needed to circulate the water and the flow rate for varying condition is decided from10,3 to 68,9 liters per hour.

  • 805.
    Wieslander Jansson, Axel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    En studie i vattenrening med elektrokoagulation: Koaguleringsförmågan hos utvalda föreningar2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Water- and energy consumption is one of humanities biggest current and future problems because of ever increasing global water consumption and because of better living conditions, increasing population and industrialization. Polluted water results in diseases, reduced life expectancy, sanitation and reduced overall health of those affected. Purifying water in an energy and environmentally effective way is therefore a must for a sustainable future.

    A study of the coagulation capabilities for a select number of organic compounds by electrocoagulation has been performed at Axolot Solutions AB. Axolot Solutions AB is a company developing electrochemical water treatment solutions, with a focus on the electrocoagulation process. The compounds that have been studied are sugars (raffinose, maltose, glucose, lactose), organic acids (formic acid, citric acid, hexanoic acid, butyric acid, octanoic acid), alcohols (1-propanol, 2-propanol), fatty acids (lecithin), others (formaldehyde, vanillin, nonylphenol, α-pinene). Industrial water coming from a debarking process was also investigated as well as two compounds that are often present in this type of water, xylan and lignin.

    The treatment efficiency was determined by measuring the COD values of the investigated water before and after the electrocoagulationprocess. Each compound was studied by using an iron anode and an aluminum anode at four different initial pH values: 4, 6, 7.5, 9. Different current densities were also studied for some of the investigated compounds.

    The results show no COD reduction for sugars, alcohols, organic acids and xylan. The process resulted in large reductions of the compounds lecithin (85.5%) and lignin (98.1%). A lesser reduction was found for the waters containing: nonylphenol (33.6%), α-pinene (42.1%) and barkwater (21.5%). A reduction of COD was also found in the water containing vanillin with an initial pH of 4 that was treated with an aluminum anode was affected. The most efficient setup for the investigated compounds varies. For that reason, no conclusion as to which initial pH and anode that should be for electrocoagulation processes in general can be drawn.

  • 806.
    Wikström, Fredrik
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Karli, Verghese
    RMIT University, Melbourne, Australia.
    Rafael, Auras
    Michigan State University, East Lansing, MI, USA.
    Olsson, Annika
    Lund University, Lund.
    Williams, Helén
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Wever, Renee
    Linköping University.
    Grönman, Kaisa
    Lappeenranta University of Technology, Lappeenranta, Finland.
    Kvalvåg Pettersen, Marit
    Nofima AS,Ås, Norway.
    Møller, Hanne
    Ostfold Research, Kråkeröy, Norway.
    Risto, Soukka
    Lappeenranta University of Technology, Lappeenranta, Finland.
    Packaging Strategies That Save Food: A Research Agenda for 20302019In: Journal of Industrial Ecology, ISSN 1088-1980, E-ISSN 1530-9290, Vol. 23, no 3, p. 532-540Article in journal (Refereed)
    Abstract [en]

    Summary Thoroughly considering and optimizing packaging systems can avoid food loss and waste. We suggest a number of issues that must be explored and review the associated challenges. Five main issues were recognized through the extensive experience of the authors and engagement of multiple stakeholders. The issues promoted are classified as follows: (1) identify and obtain specific data of packaging functions that influence food waste; (2) understand the total environmental burden of product/package by considering the trade‐off between product protection and preservation and environmental footprint; (3) develop understanding of how these functions should be treated in environmental footprint evaluations; (4) improve packaging design processes to also consider reducing food waste; and (5) analyze stakeholder incentives to reduce food loss and waste. Packaging measures that save food will be important to fulfill the United Nations Sustainable Development goal to halve per capita global food waste at the retail and consumer levels and to reduce food losses along production and supply chains.

  • 807.
    Wikström, Fredrik
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Williams, Helén
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Packaging and Food Waste Behavior2017In: Reference Module in Food Sciences, Elsevier, 2017, p. 1-4Chapter in book (Refereed)
    Abstract [en]

    Packaging saves food by protecting the content from physical and chemical degradation during the distribution and storage processes. However, packaging can do much more than that. This article explores how the design of a package may help, or indeed hinder, the consumer to avoid wasting food. A number of packaging attributes influence consumer behavior. The influence is different depending on the product‘s characteristics and the needs of the consumer. For many products, it might be better to add packaging material, for example, by creating smaller sizes of the product to reduce food waste and the overall environmental impact.

  • 808.
    Wikström, Fredrik
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Williams, Helén
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Govindarajan, Venkatesh
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    The influence of packaging attributes on recycling and food waste behaviour – An environmental comparison of two packaging alternatives2016In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 137, p. 895-902Article in journal (Refereed)
    Abstract [en]

    This paper analyses how user behaviour influences the environmental comparison of two different packages for minced meat - a lightweight tube and a tray. The direct and indirect environmental effects are evaluated using simplified LCA. A number of packaging attributes with regard to food waste and recycling behaviour are analysed for the packages, and then used for the scenario calculations. The results show that the tube is the superior environmental alternative when only the direct effects are considered. When indirect effects and user behaviour are included in the comparison, the tray is the better alternative due to higher recycling rates and, most importantly, less food waste during the process of emptying. However, the environmental impacts due to the food waste in the tube may be compensated for, if the longer shelf-life of the tube results in lower wastage in the households. It is concluded that indirect environmental effects and user behaviour should be included in environmental assessments of packaging to obtain meaningful results.

  • 809.
    Wikström, Fredrik
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Williams, Helén
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Trischler, Jakob
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Service Research Center (from 2013).
    Rowe, Zane
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    The importance of packaging functions for food waste of different products in households2019In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 11, no 9, p. 1-16, article id 2641Article in journal (Refereed)
    Abstract [en]

    The United Nations sustainability goal SDG 12.3 is to reduce the amount of food that is wasted by half, due to environmental and social reasons. This paper aims to analyse the most important packaging functions that affect food waste in households for different products, as the reason for wastage can be expected to differ between different products. The reasons for food wastage of different categories and products have been compiled through literature studies, and possible improvements of packaging functions to reduce food waste have been identified. In addition, an expert workshop judged the most important packaging functions to reduce food waste for a number of products. They also discussed the obstacles and possibilities to realise the packaging improvements. This study confirms that how packaging functions influence food waste on the product level is a highly unexplored question. Most likely, there is high potential to reduce food waste through better adaptions of packaging functions to user needs and habits. Both the literature study and the expert workshop show that less food per pack and better information regarding food safety and storage have high potential to reduce food waste, but also that product specific considerations are necessary.

  • 810.
    Wilke, Caroline
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). BTG Instruments.
    The Impact of Dissolved Matter on Fiberline Processes2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The impact of dissolved matter on the performance of four fiberline process stages was investigated: oxygen delignification, hot acid treatment, chlorine dioxide bleaching, and hydrogen peroxide reinforced alkaline extraction. In particular the impact on delignification due to dissolved lignin was studied.

    The impact of unoxidized and oxidized dissolved matter on lignin and carbohydrate degradation was investigated in a laboratory oxygen delignification stage. It was concluded that the delignification was decreased by the presence of unoxidized dissolved matter but increased in the case of oxidized dissolved matter. Both types of dissolved matter comparably increased the carbohydrate degradation. Thus, the presence of unoxidized dissolved matter impaired the selectivity. In the case of oxidized dissolved matter, the selec­tiv­ity was affected in the same way as when using a higher sodium hydroxide charge.

    The presence of dissolved matter reduced the efficiency of a laboratory hot acid stage, and subsequently further affected the chemical demand in a following chlorine dioxide stage. In a laboratory chlorine dioxide stage, the presence of dissolved matter reduced the delignifica­tion. The additional chemical demand required to compensate for this reduc­tion was proportional to the content of dissolved matter. Moreover, the total chemical demand was found proportional to the total kappa number of the pulp, that is the sum of the fiber and filtrate kappa numbers. Finally, the presence of dissolved matter in a laboratory hydrogen peroxide reinforced alkaline extrac­tion stage reduced both the delignification and the brightness.

    Furthermore, mill studies showed that the content of dissolved lignin varied significantly, and often more than the fiber-bound lignin, in a bleaching stage. For chlorine dioxide stages, it was proposed that the chemical consumption could be reduced by controlling the chemical charge based on the sum of the fiber-bound lignin and the dissolved lignin.

  • 811.
    Wilke, Caroline
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Andersson, Niclas
    BTG Instruments AB.
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Impact of dissolved matter in the oxygen delignification stage2017In: TAPPI Journal, ISSN 0734-1415, Vol. 16, no 5, p. 275-284Article in journal (Refereed)
    Abstract [en]

    The presence of dissolved matter in the pulp suspension in an oxygen (O-2) delignification stage, consisting mainly of dissolved lignin, is normally considered to negatively affect the delignification rate due to the competing reactions between the fiber bound lignin and the lignin dissolved in the filtrate. Recirculated oxidized filtrate from the post-O-2 washing is usually considered to be less harmful to the delignification efficiency than unoxidized dissolved matter originating from the cooking stage. To develop a better understanding of the mechanisms of the dissolved matter's reactions and impact on the O-2 stage performance, laboratory oxygen delignification experiments with varying levels of unoxidized and oxidized dissolved matter were conducted. The results showed that unoxidized dissolved matter had a negative impact on the delignification in the O-2 stage, whereas oxidized dissolved matter actually had a positive effect. The delignification efficiency of the laboratory experiments thus depends on both the amount of dissolved matter and its origin. The pulp viscosity decreased with increasing dissolved matter content irrespective of its origin but at higher COD levels; however, the viscosity drop was larger for the unoxidized dissolved matter. In terms of selectivity, the oxidized filtrate had a similar impact as additional NaOH charge. Both types of filtrates consumed hydroxide and the final pH decreased with increasing dissolved matter content. The final pH was significantly lower in the unoxidized filtrate experiments at higher COD levels, indicating a high reactivity between the unoxidized dissolved matter and the oxygen in the reactor. Based on the results, further understanding is achieved about the relation between pre-O-2 washing performance and process configuration in an actual mill case, as well as the impact of dissolved matter on delignification. The importance of efficient removal of harmful unoxidized dissolved matter is verified, but the results also suggest that the oxidized dissolved matter that is recirculated from post-O-2 washing actually has a significant positive impact on the delignification and is not just a potential problem in case of carryover to the bleach plant. Subsequently, pulp washing efficiency is critical both pre- and post-O-2.

  • 812.
    Wilke, Caroline
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). BTG Instruments.
    Andersson, Niclas
    BTG Instruments.
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Impact of dissolved organic matter in DO-and ADO-stages in bleaching of birch kraft pulp2019In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 34, no 4, p. 433-441Article in journal (Refereed)
    Abstract [en]

    To be able to charge a correct amount of chlorine dioxide in the D-0-stage, a pulp mill needs good control of the bleaching process and good sensors to keep the variability of the bleaching result on an acceptable level. It is also important to include the bleaching agent demand from the dissolved matter in the pulp slurry. If this is done correctly, over- or undercharging of bleaching agents can be reduced, which lead to lower bleaching chemical cost, lower polluting emissions and higher pulp quality. Our previous research has shown that the dissolved organic carryover from the O-2-stage varies significantly when bleaching softwood kraft pulp. The present study investigated the corresponding impact in the case of bleaching of birch pulp. Different mill configurations and process conditions have been simulated in laboratory trials, including proceeding A-stage treatment, different degrees of washing before and between the stages, and a comparison of the effects of recycled and non-recycled wash filtrates. The results have confirmed the significant impact of the dissolved organic matter, and the knowledge which have been generated can be used to understand how measurement and control concepts can be developed to improve the pulp quality control and to decrease production cost.

  • 813.
    Wilke, Caroline
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). BTG Instruments.
    Andersson, Niclas
    BTG Instruments.
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Impact of dissolved organic matter in hydrogen peroxide reinforced alkaline extraction stages2019In: Appita journal, ISSN 1038-6807, Vol. 72, no 1, p. 4-14Article in journal (Refereed)
    Abstract [en]

    It has been demonstrated in previous studies that carryover of dissolved organic matter to a following bleaching stage has a significant impact on the reactions in oxygen delignification and chlorine dioxide stages. Since hydrogen peroxide is commonly used in the bleach plant in various positions, the present study was conducted to investigate the impact of dissolved matter on the performance of a hydrogen peroxide reinforced alkaline extraction stage. The results of a study using an OD(EP) bleaching sequence showed that chlorine dioxide filtrates have a negative impact on delignification and brightening. In the case studied, the kappa number after the laboratory (EP)-stage was up to 26% higher and the brightness was up to 10% ISO lower when carryover of dissolved matter from a chlorine dioxide stage was present. Compensating for these reductions by increasing the sodium hydroxide charge improved the brightness significantly less than the delignification.

  • 814.
    Wilke, Caroline
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). BTG Instruments.
    Andersson, Niclas
    BTG Instruments.
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Oxygen delignification: Laboratory evaluation of the impact of dissolved organic matter, sodium car­bonate and sodium thiosulfate2019In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 73, no 7, p. 645-652Article in journal (Refereed)
    Abstract [en]

    Dissolved matter (DM) in the oxygen delignification (O2Del) stage affects the lignin and carbohydrate degradation. To understand this topic better, laboratory O2Del experiments were conducted with controlled addition of either unoxidized dissolved matter (UnoxDM) originating from the cooking stage or oxidized dissolved matter (OxDM) recycled from the post-O2Del washing. The presence of UnoxDM decreased the delignification, while the presence of OxDM showed the opposite effect, both compared to a well-washed pulp and at the same alkali charge level. However, both types of DM had a negative impact on the carbohydrate degradation. The distribution between these DMs will affect the resulting lignin degradation, because the filtrate accompanying the fibers into the O2Del stage is a mixture of UnoxDM and OxDM. It is proposed that the positive impact on the delignification by OxDM is due to the high carbonate ion concentration in the filtrate. Further, the high content of thiosulfate ions in the UnoxDM was one of the reasons for the lower delignification in its presence.

  • 815.
    Wilke, Caroline
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. BTG Instruments AB, Saffle, Sweden..
    Andersson, Niclas
    BTG Instruments AB, R&D & Business Dev, Saffle, Sweden..
    Van Fleet, Rick
    BTG Amer Inc, Fiber Line, Norcross, GA USA..
    Mathur, Akhlesh
    BTG Instruments, BTG Asia Fiber Segment & SEA, Singapore, Singapore..
    Germgard, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Impact of dissolved lignin in oxygen delignification and chlorine dioxide stages2016In: TAPPI Journal, ISSN 0734-1415, Vol. 15, no 3, p. 167-174Article in journal (Refereed)
    Abstract [en]

    While carryover of dissolved lignin between stages in the pulp mill fiber line is a well-known problem, it is still typically seen only as a minor disturbance factor or bias in the control of oxygen (O-2) delignification and bleaching stages. The present study, however, reveals that it plays a larger role than anticipated, and that it should be properly analyzed in order to correctly control the process stages. This is especially important for the O-2 and D-0 stages as the lignin content is still high in these positions. The results of the study show that dissolved lignin carried over between stages may have a significant impact on the bleaching chemical consumption and, indirectly, on the pulp quality. Mill investigations have shown very large variations in the dissolved lignin content in the pulp before the oxygen delignification stage and before the D-0 stage that have significantly influenced the bleaching chemical demand and, subsequently, the degree of delignification. In order to develop a better understanding of the mechanisms of the dissolved lignin's reactions, laboratory O-2 and D-0 experiments with controlled levels of dissolved lignin were conducted. It was anticipated that a better feedforward control could be achieved using an online dissolved lignin measurement, and results from mill trials are presented. Chlorine dioxide laboratory experiments using different levels of carryover (i.e., different dissolved lignin contents) were conducted. It was concluded that the filtrate kappa number provides a relevant measure of the bleach demand due to the dissolved lignin and that, subsequently, the combined fiber and filtrate kappa number provides an appropriate measure for optimum feedforward control of the stages. Mill results support these findings, which show that the chemical consumption is reduced significantly using the total kappa number. The post-D or post-DE kappa number feedback control can most probably be eliminated by using this technology.

  • 816.
    Williams, Helén
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Global market trends and how packaging can support for reducing food waste2013In: International Research Workshop on Food Waste Prevention. Oslo 19th November 2013, 2013Conference paper (Refereed)
    Abstract [en]

    In order to feed an increasing world population with good and safe food it is important to reduce the amount of food waste. The global population is expected to grow to 9 billion and over the same period food production will be under threat from climate change, competing land uses, erosion and diminishing supplies of clean water. Packaging plays an important role in containing and protecting the food as it moves from agriculture to households. This work is a summary from an international literature review and interviews from 15 organisations in the Australian food and packaging supply chain. It considers food waste in the supply chain with emphasis on food waste prior to consumption, and also food rescue through charities.

    A number of global trends and there effect on packaging development for reducing food waste was identified and analysed, these include:

    Longer supply chains-With longer supply chains there are increased risks of product damage which make the packaging even more critical. Distribution packaging should provide better protection and shelf life for fresh produce as it moves from the farm to the processor, wholesaler or retailer. This may require the development of tailored solutions for individual products. This also requires more collaboration between manufacturers and retailers to improve the industry’s understanding of food waste in the supply chain. More use of intelligent packaging and data sharing can be useful .

    More on-line shopping- Online expenditure in Australia was estimated to be around $8.4 billion in 2010 and is forecast to reach $26.9 billion by 2016. Online shopping requires more secondary packaging to protect the product during transport from the retail or manufacturer to the household, but it doesn’t need to be ‘shelf ready’ which may save resources. This increases the amount of packaging requiring recycling in the home but there could be some potential benefits for food waste.

    Consumption of meals out of the home- This trend shifts waste away from the home to a restaurant and/or processing facility and may give both pros and cons for reducing food waste and how packaging are recycled.    

    More small households- Product and packaging development need to cater for smaller households. Single and smaller serve products will reduce waste by meeting the needs of single and two person households, however this need to be environmentally analysed in relation to increased amount of packaging. . 

    More convenience- The trend from loose fresh produce to more pre-packed and processed food products has implications for packaging. With a better primary packaging a simpler and less robust secondary packaging may be sufficient. This may require adoption of new packaging materials and technologies, such as modified atmosphere packaging and oxygen scavengers, to extend the shelf life of foods.

    Food recovery for charity- It is important with distribution packaging that supports recovery of surplus and unsaleable fresh produce from farms and redirects it to food rescue organisations. These packaging systems will need to be flexible to accommodate the transport of bulk quantities from farm to food recovery organisations, as well as smaller orders from distribution centres to individual charities. The issue need to be addressed when developing new secondary packaging.

    The packaging itself also needs to be recoverable to minimise overall environmental impacts in the country where it is consumed.  

  • 817.
    Williams, Helén
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Verghese, Karli
    Centre for Design and Society, School of Architecture and Design, RMIT University, Australia.
    Lockrey, Simon
    Centre for Design and Society, School of Architecture and Design, RMIT University, Australia.
    Crossin, Enda
    Centre for Design and Society, School of Architecture and Design, RMIT University, Australia.
    Clune, Stephen
    ImaginationLancaster, Lancaster University, UK.
    Rio, Maud
    Centre for Design and Society, School of Architecture and Design, RMIT University, Australia.
    Wikström, Fredrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    The greenhouse gas profile of a “Hungry Planet”; quantifying the impacts of the weekly food purchases including associated packaging and food waste of three families2014Conference paper (Refereed)
    Abstract [en]

    The United Nations Food and Agricultural Organisation (FAO) have estimated that 1.3 billion tonnes of food is wasted across the supply chain, while food security emerges as one of the leading challenges facing a growing global population. Life cycle assessment (LCA) can illustrate the environmental implications of food production, consumption and waste. In 2005, Peter Menzel and Faith D’Aluisio presented a photographic study in “Hungry Planet – What the World Eats” documenting what thirty families across twenty-four countries ate during the course of one week. The weekly food purchasing inventories of three of these families have been combined with LCA data to report the greenhouse gas intensity of these food purchases. The greenhouse gas emission profile including those of 128 varieties of fresh food, along with data on packaging material production and household food waste, have been used in the calculations. The paper will present the findings illustrating the contribution each component has: food, packaging and food waste; and will also discuss the implications for food packaging design. 

  • 818.
    Williams, Helén
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Wikstrom, Fredrik
    Örebro University.
    Wetter-Edman, Katarina
    Örebro University.
    Kristensson, Per
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Social and Psychological Studies (from 2013).
    Decisions on Recycling or Waste: How Packaging Functions Affect the Fate of Used Packaging in Selected Swedish Households2018In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 10, no 12, article id 4794Article in journal (Refereed)
    Abstract [en]

    The intention of this paper is to learn more about why consumers choose whether or not to recycle, with special attention given to the functions of the packaging itself, in order to provide suggestions for improvements in packaging design, recycling systems and the environmental assessment of different packaging designs. The study focussed on ten households in Sweden that where motivated to participate in the study in order to gain an understanding of the complex matter of this decision-making process. The intention of implementing an interview-based qualitative study was to gain rich data and to reach beyond the respondents' immediate verbal responses. The respondents were interviewed with open-ended questions, which were supported with pictures of packaging; additionally, their waste bins were examined. This explorative study suggests a set of obstacles that cause consumers to dispose of packaging relating to the functions of packaging. The different obstacles that determine whether or not packaging is recycled were organised according to three different themes: the attitude towards cleanliness, the effort required to clean and sort and uncertainties about the best environmental alternative. The different functions of packaging do in fact influence all of the identified themes and; therefore, influence the decisions consumers make with regards to the recycling of specific packaging. The identified packaging functions were easy toseparate different materials, easy to separate different parts, easy to clean,easy to empty, easy to reseal, easy to compress and communication regarding recycling. Consumer behaviour with regards to specific packaging functions and recycling should be further investigated. It should also be considered for inclusion in design processes, to increase the chance of materials being recycled, and in food-packaging life-cycle assessments, to provide results that align more closely with reality.

  • 819.
    Williams, Helén
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Wikström, Fredrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Lindström, Annika
    RICE, Sweden.
    Wickholm, Kristina
    RICE, Sweden.
    Lorentzon, Ann
    RICE, Sweden.
    Investigation of consumer attitudes, practices and food waste for three food items, to use as input in new packaging designs that aim to reduce food waste2017In: 28th IAPRI World Symposium on Packaging, 2017, p. 1-7Conference paper (Refereed)
    Abstract [en]

    A wide range of measures is required to tackle the global food waste problem. Innovative packaging, which helps to reduce food waste, is one important measure. The data for food waste is often presented in a summarised way. However, different food products are wasted for different reasons. In a Swedish project, actors along the entire value chain collaborated to develop new packaging solutions to reduce food waste of three products: salsa in glass jars, mixed lettuce in plastic packaging and rice pudding in plastic packaging. Waste levels and reasons for waste were examined in waste audits of the businesses, in ethnographic studies and in interviews with consumers at retail stores.

    This study showed that consumers wasted the products to a much higher extent than the waste which occurred during filling, transport and retail. Waste levels among consumers varied from 0-75%, which is notably high, given that consumers tend to underestimate or not admit to wasting food. The mixed lettuce and rice pudding are both intended to be packaged in appropriate serving sizes; however, only 27% of the mixed lettuce and 50% of the rice pudding was consumed in one sitting. Respondents mentioned some material features and several handling functions of packaging, but very few commented on the protection that the packaging provides. Few, if any, expressed any recognition of packaging attributes, which helped to avoid food waste.

    The respondents mentioned that wasting food was a waste of money and that it can have a negative effect on conscience; despite that, respondents also said that they wanted a variety of meals and to not have the same food several days during the same week.

  • 820.
    Witos, Joanna
    et al.
    Univ Helsinki, Dept Chem, Chem Anal Lab, FIN-00014 Helsinki, Finland..
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Cilpa-Karhu, Geraldine
    Univ Helsinki, Dept Chem, Chem Anal Lab, FIN-00014 Helsinki, Finland..
    Metso, Jari
    Nat Inst Hlth & Welf, Publ Hlth Genom Unit, Biomedicum, FIN-00290 Helsinki, Finland..
    Jauhiainen, Matti
    Nat Inst Hlth & Welf, Publ Hlth Genom Unit, Biomedicum, FIN-00290 Helsinki, Finland..
    Riekkola, Marja-Liisa
    Univ Helsinki, Dept Chem, Chem Anal Lab, FIN-00014 Helsinki, Finland..
    Partial filling affinity capillary electrophoresis including adsorption energy distribution calculations: towards reliable and feasible biomolecular interaction studies2015In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 140, no 9, p. 3175-3182Article in journal (Refereed)
    Abstract [en]

    In this work, a method to study and analyze the interaction data in free solution by exploiting partial filling affinity capillary electrophoresis (PF-ACE) followed by adsorption energy distribution calculations (AED) prior model fit to adsorption isotherms will be demonstrated. PF-ACE-AED approach allowed the possibility to distinguish weak and strong interactions of the binding processes between the most common apolipoprotein E protein isoforms (apoE2, apoE3, apoE4) of high density lipoprotein (HDL) and apoE-containing HDL2 with major glycosaminoglycan (GAG) chain of proteoglycans (PGs), chondroitin-6-sulfate (C6S). The AED analysis clearly revealed the heterogeneity of the binding processes. The major difference was that they were heterogeneous with two different adsorption sites for apoE2 and apoE4 isoforms, whereas interestingly for apoE3 and apoE-containing HDL2, the binding was homogeneous (one site) adsorption process. Moreover, our results allowed the evaluation of differences in the binding process strengths giving the following order with C6S: apoE-containing HDL2 > apoE2 > apoE4 > apoE3. In addition, the affinity constant values determined could be compared with those obtained in our previous studies for the interactions between apoE isoforms and another important GAG chain of PGs - dermatan sulfate (DS). The success of the combination of AED calculations prior to non-linear adsorption isotherm model fit with PF-ACE when the concentration range was extended, confirmed the power of the system in the clarification of the heterogeneity of biological processes studied.

  • 821. Zaki, Hazem
    et al.
    Almssad, Asaad
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. Archcrea Institute.
    Thermal earth inertia such a source of energy for bio-sustainable house2005In: The International Conference Sustainable Building 2005 SB05, Tokyo: SB05Tokyo National Conference Board , 2005, p. 150-153Conference paper (Refereed)
    Abstract [en]

    The earth is our sustainer, the chain of ecologic survival. Renew ability is the key to our human continuum and our prime resource for architecture. Earth sheltering earth handling and earth escaping are more clearly pronounced in the vocabulary of architectural planning and design  . Many of us had percept the positive effect in underground tunnels by traveling through the metro. The vital and efficient sustainable energy which can be used by us is underground thermal inertia; we can become aware of that, the earth can serve in many climates as a heating or cooling source. Its high thermal capacity keeps the soil temperature, below a certain depth, considerably lower than the ambient air temperature during summer and higher than the ambient air temperature during winter. Seasonal variation of the earth temperature decreases with increase of depth, moisture content of soil and soil conductivity. It is estimated that a small number of meters below the earth surface, the earth temperature remains constant during the year. In regions with temperate climate such as Denmark, the temperature of the soil at depth of 2-3 meters can be low enough during summer or high enough during winter, to serve as a cooling or heating source. Using of the underground constant temperature can be useful for architects and designer because the temperature is between 8ºC-13ºC, and2- 3 m above the earth, can help us to find a competent solution which help us to controlled thermal comfort in houses.

  • 822.
    Zdanowicz, Magdalena
    et al.
    West Pomeranian University Technolgy, Polen.
    Johansson, Caisa
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Impact of additives on mechanical and barrier properties of starch-based films plasticized with deep eutectic solvents2017In: Starke (Weinheim), ISSN 0038-9056, E-ISSN 1521-379X, Vol. 69, no 11-12, article id UNSP 1700030Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to prepare starch-based films plasticized with two and three-component deep eutectic solvents (DES) in the presence of different additives:aluminosilicates (sodium and calcium montmorillonite), microcrystalline cellulose, and tannin; and to investigate their influence on mechanical and barrier properties of the films. Mutual interactions between polysaccharide matrix, plasticizer, and additive were investigated by Fourier transform infrared (FTIR) spectroscopy. Two types of starches were used:native potato starch (TPS) and hydroxypropylated, oxidized potato starch (HOPS). The two-component DES CC:G consisted of choline chloride (CC) and glycerol (G), whereas the three-component DES with crosslinking activity CCit:U:G, included choline citrate (CCit), urea (U), and glycerol. For the TPS/CCit:U:G films an improvement of the mechanical and barrier properties was obtained after introduction of additives, whereas for TPS/CC:G only a slight decrease in water vapor transmission rate was observed, without any significant improvement in mechanical properties. Moreover, the mechanical test results, FTIR spectra, and the oxygen transmission rate values revealed that the clays interacted with plasticizer components, thereby hindering crosslinking reactions between plasticizer and starch.

  • 823.
    Zdanowicz, Magdalena
    et al.
    West Pomeranian Univ Technol, Inst Polymer, Ul Pulaskiego 10, PL-70322 Szczecin, Poland.
    Johansson, Caisa
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Mechanical and barrier properties of starch-based films plasticized with two- or three component deep eutectic solvents2016In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 151, p. 103-112Article in journal (Refereed)
  • 824.
    Zethelius, Thea
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Natriumkarbonat som alternativ alkalikälla till natriumhydroxid: Impregnering och blekning av kemitermomekanisk massa2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The objective of this project was to see if it is possible to replace sodium hydroxide with sodium carbonate as an alkali source on the CTMP line, and it was done on behalf of the Stora Enso Skoghall Mill. The areas that were studied were the impregnation and bleaching of CTMP and also the handling of sodium carbonate solution.

    The solubility of sodium carbonate at various temperatures was confirmed, bleaching of CTMP with sodium hydroxide and sodium carbonate, titration of the sodium hydroxide and sodium carbonate against sodium bisulfite solution and a simpler laboratory impregnation was performed. Aspects of equipment, costs and the possibility of precipitation of calcium carbonate were also studied.

    The results indicate that more sodium carbonate is needed than one thought for the substitution to be possible, and that it also becomes more expensive. There is a possibility that other parts of the mill can perform the replacement of alkali and go with greater profit than the CTMP line goes with loss. Experiments also showed an increase in temperature when preparing the sodium carbonate solution, precipitation of natron and the need for the existing equipment to be supplemented on the basis of recommendations from the chemical supplier. Previous studies showed possible deterioration of the paper quality when bleaching CTMP with sodium carbonate.

    Although sodium carbonate is a cheaper alternative to sodium hydroxide, and that it would theoretically work well as a substitute, it is much that one has to take into consideration in terms of using sodium carbonate and it is necessary to think things through before usage, so that things can be done properly. Based on the results, it is shown that the swap of alkali will be suboptimal.

  • 825.
    Zhang, Y.
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Forssén, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Gulliksson, M.
    Orebrov Univ, Sch Sci & Technol, Dept Math, Orebro, Sweden.
    Dai, X.
    Zhejiang Univ, City Coll, Sch Comp Sci, Hangzhou, Zhejiang, Peoples R China.
    An adaptive regularization algorithm for recovering the rate constant distribution from biosensor data2018In: Inverse Problems in Science and Engineering, ISSN 1741-5977, E-ISSN 1741-5985, Vol. 26, no 10, p. 1464-1489Article in journal (Refereed)
    Abstract [en]

    We present here the theoretical results and numerical analysis of a regularization method for the inverse problem of determining the rate constant distribution from biosensor data. The rate constant distribution method is a modern technique to study binding equilibrium and kinetics for chemical reactions. Finding a rate constant distribution from biosensor data can be described as a multidimensional Fredholm integral equation of the first kind, which is a typical ill-posed problem in the sense of J. Hadamard. By combining regularization theory and the goal-oriented adaptive discretization technique, we develop an Adaptive Interaction Distribution Algorithm (AIDA) for the reconstruction of rate constant distributions. The mesh refinement criteria are proposed based on the a posteriori error estimation of the finite element approximation. The stability of the obtained approximate solution with respect to data noise is proven. Finally, numerical tests for both synthetic and real data are given to show the robustness of the AIDA.

  • 826.
    Zhang, Ye
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Orebro Univ, Sch Sci & Technol, Dept Math, Orebro, Sweden.
    Lin, G.
    Zhejiang Univ, Dept Math, Hangzhou, Zhejiang, Peoples R China..
    Gulliksson, M.
    Orebro Univ, Sch Sci & Technol, Dept Math, Orebro, Sweden..
    Forssén, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Cheng, X.
    Zhejiang Univ, Dept Math, Hangzhou, Zhejiang, Peoples R China..
    An adjoint method in inverse problems of chromatography2017In: Inverse Problems in Science and Engineering, ISSN 1741-5977, E-ISSN 1741-5985, Vol. 25, no 8, p. 1112-1137Article in journal (Refereed)
    Abstract [en]

    How to determine adsorption isotherms is an issue of significant importance in chromatography. A modern technique of obtaining adsorption isotherms is to solve an inverse problem so that the simulated batch separation coincides with actual experimental results. In this work, as well as the natural least-square approach, we consider a Kohn-Vogelius type formulation for the reconstruction of adsorption isotherms in chromatography, which converts the original boundary fitting problem into a domain fitting problem. Moreover, using the first momentum regularizing strategy, a new regularization algorithm for both the Equilibrium-Dispersive model and the Transport-Dispersive model is developed. The mass transfer resistance coefficients in the Transport-Dispersive model are also estimated by the proposed inverse method. The computation of the gradients of objective functions for both of the two models is derived by the adjoint method. Finally, numerical simulations for both a synthetic problem and a real-world problem are given to show the robustness of the proposed algorithm.

  • 827.
    Zhang, Ye
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Örebro Universitet Sverige.
    Lin, Guang-Liang
    Zhejiang Univ, Dept Math, Hangzhou 310027, Zhejiang, Peoples R China..
    Forssén, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Gulliksson, Marten
    Örebro Universitet, Sweden..
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Cheng, Xiao-Liang
    Zhejiang Univ, Dept Math, Hangzhou 310027, Zhejiang, Peoples R China..
    A regularization method for the reconstruction of adsorption isotherms in liquid chromatography2016In: Inverse Problems, ISSN 0266-5611, E-ISSN 1361-6420, Vol. 32, no 10, article id 105005Article in journal (Refereed)
    Abstract [en]

    Determining competitive adsorption isotherms is an open problem in liquid chromatography. Since traditional experimental trial-and-error approaches are too complex and expensive, a modern technique of obtaining adsorption isotherms is to solve the inverse problem so that the simulated batch separation coincides with actual experimental results. This is a typical ill-posed problem. Moreover, in almost all cases the observed concentration at the outlet is the total response of all components, which makes the problem more difficult. In this work, we tackle the ill-posedness with a new regularization method, which is based on the fact that the adsorption isotherms do not depend on the injection profile. The proposed method transfers the original problem to an optimization problem with a time-dependent convection-diffusion equation constraint. Iterative algorithms for solving constraint optimization problems for both the equilibrium-dispersive and the transport-dispersive models are developed. The mass transfer resistance is also estimated by the proposed inverse method. A regularization parameter selection method and the convergence property of the proposed algorithm are discussed. Finally, numerical tests for both synthetic problems and real-world problems are given to show the efficiency and feasibility of the proposed regularization method.

  • 828.
    Åsberg, Dennis
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Fundamental and Regulatory Aspects of UHPLC in Pharmaceutical Analysis2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ultra-high performance liquid chromatography (UHPLC) provides a considerable increase in throughput compared to HPLC and a reduced solvent consumption. The implementation of UHPLC in pharmaceutical analysis, e.g. quality control, has accelerated in recent years and there is currently a mix of HPLC and UHPLC instrumentation within pharmaceutical companies. There are, however, technical and regulatory challenges converting a HPLC method to UHPLC making it difficult to take full advantage of UHPLC in regulatory-focused applications like quality control in pharmaceutical production.

    Using chromatographic modelling and fundamental theory, this thesis investigated method conversion between HPLC and UHPLC. It reports on the influence of temperature gradients due to viscous heating, pressure effects and stationary phase properties on the separation performance. It also presents a regulatory concept for less regulatory interaction for minor changes to approved methods to support efficient life cycle management.

    The higher pressure in UHPLC gave a retention increase of up to 40% as compared to conventional HPLC while viscous heating, instead, reduced retention and the net result was very solute dependent. Selectivity shifts were observed even between solutes with similar structure when switching between HPLC and UHPLC and an experimental method to predict such selectivity shifts was therefore developed. The peak shape was negatively affected by the increase in pressure for some solutes since secondary interactions between the solute and the stationary phase increased with pressure.

    With the upcoming ICH Q12 guideline, it will be possible for the industry to convert existing methods to UHPLC in a more flexible way using the deeper understanding and the regulatory concept presented here as a case example.

  • 829.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Chutkowski, Marcin
    Rzeszów University of Technology, Polen.
    Leśko, Marek
    Rzeszów University of Technology, Polen.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Kaczmarski, Krzysztof
    Rzeszów University of Technology, Polen.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    A practical approach for predicting retention time shifts due to pressure and temperature gradients in ultra-high-pressure liquid chromatography2017In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1479, p. 107-120Article in journal (Refereed)
    Abstract [en]

    Large pressure gradients are generated in ultra-high-pressure liquid chromatography (UHPLC) using sub–2 μm particles causing significant temperature gradients over the column due to viscous heating. These pressure and temperature gradients affect retention and ultimately result in important selectivity shifts. In this study, we developed an approach for predicting the retention time shifts due to these gradients. The approach is presented as a step-by-step procedure and it is based on empirical linear relationships describing how retention varies as a function of temperature and pressure and how the average column temperature increases with the flow rate. It requires only four experiments on standard equipment, is based on straightforward calculations, and is therefore easy to use in method development. The approach was rigorously validated against experimental data obtained with a quality control method for the active pharmaceutical ingredient omeprazole. The accuracy of retention time predictions was very good with relative errors always less than 1% and in many cases around 0.5% (n = 32). Selectivity shifts observed between omeprazole and the related impurities when changing the flow rate could also be accurately predicted resulting in good estimates of the resolution between critical peak pairs. The approximations which the presented approach are based on were all justified. The retention factor as a function of pressure and temperature was studied in an experimental design while the temperature distribution in the column was obtained by solving the fundamental heat and mass balance equations for the different experimental conditions. We strongly believe that this approach is sufficiently accurate and experimentally feasible for this separation to be a valuable tool when developing a UHPLC method. After further validation with other separation systems, it could become a useful approach in UHPLC method development, especially in the pharmaceutical industry where demands are high for robustness and regulatory oversight.

  • 830.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Enmark, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Evaluation of co-solvent fraction, pressure and temperature effects in analytical and preparative supercritical fluid chromatography2014In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1374, p. 254-260Article in journal (Refereed)
    Abstract [en]

    Abstract A chemometric approach is used for studying the combined effect of temperature, pressure and co-solvent fraction in analytical and preparative supercritical fluid chromatography (SFC). More specifically, by utilizing design of experiments coupled with careful measurements of the experimental conditions the interaction between pressure, temperature and co-solvent fraction was studied with respect to productivity, selectivity and retention in chiral SFC. A tris-(3,5-dimethylphenyl) carbamoyl cellulose stationary phase with carbon dioxide/methanol as mobile phase and the two racemic analytes trans-stilbene oxide (TSO) and 1,1′-bi-2-naphthol (BINOL) were investigated. It was found for the investigated model system that the co-solvent fraction and pressure were the parameters that most affected the retention factors and that the co-solvent fraction and column temperature were most important for controlling the selectivity. The productivity in the preparative mode of SFC was most influenced by the co-solvent fraction and temperature. Both high co-solvent fraction and temperature gave maximum productivity in the studied design space.

  • 831.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Karlsson, Anders
    AstraZeneca R and D, Mölndal, Sweden.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Kaczmarski, Krzysztof
    Poland.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Analytical method development in the quality by design framework2014In: American Laboratory, ISSN 0044-7749, Vol. 46, no 9, p. 12-15Article in journal (Refereed)
    Abstract [en]

    The development of analytical methods in the Quality by Design (QbD) framework is currently gaining great momentum in the pharmaceutical industry. Presented here is a case study in which a pharmaceutical Quality Control (QC) method was developed using HPLC. The possibilities of continuous improvements during the method’s lifetime are demonstrated by switching to ultrahigh performance liquid chromatography (UHPLC).

  • 832.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Lesko, Marek
    Rzeszow University of Technology.
    Enmark, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Forssén, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Kaczmarski, Krzysztof
    Rzeszow University of Technology.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Prediction of Overloaded Profiles in Gradient Elution Chromatography2013Conference paper (Other academic)
    Abstract [en]

    This poster is a compliment to the oral presentation “A new procedure for improved predictions of overloaded profiles in gradient elution”. In order to simulate the separation process in liquid chromatography the competitive adsorption isotherms need to be known. In gradient elution the adsorption isotherms are determined with isocratic experiments on different mobile-phase plateaus that covers the range used in the gradient program. This can lead to extreme retention times for some mobile-phase compositions and therefore it might even be impossible to determine all necessary adsorption data using the traditional isocratic approach. We present a method where single and competitive nonlinear adsorption isotherms are determined directly from overloaded elution profiles in gradient elution. The numerical coefficients in the adsorption isotherms are determined by the inverse method that minimizes the difference between the calculated and the experimental elution profiles. This is an extension of the inverse method where the need for tedious/impossible isocratic experiments is eliminated. The method is systematically verified using both synthetic and experimental data. Finally the new method is used to successfully predict elution profiles for a two-component mixture in gradient elution. The new method makes it possible to study the adsorption of substances whose retention factor vary strongly with the mobile-phase composition, like peptides and proteins, where the classic methods will fail. A similar situation occurs in SFC and the proposed approach could with modifications probably be used also there. This is a contribution from the Fundamental Separation Science Group www.FSSG.se

  • 833.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Lesko, Marek
    Leek, Tomas
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Kaczmarski, Krzysztof
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Estimation of Nonlinear Adsorption Isotherms in Gradient Elution RP-LC of Peptides in the Presence of an Adsorbing Additive2017In: Chromatographia, ISSN 0009-5893, E-ISSN 1612-1112, Vol. 80, no 6, p. 961-966Article in journal (Refereed)
    Abstract [en]

    In electrostatic repulsive interaction chromatography, using a charged surface hybrid sorbent carrying positive charges can improve the peak shape of peptides in reversed-phase liquid chromatography (RP-LC), especially in overloaded conditions, compared with standard C-18 sorbents. However, the positive surface charges can interact with anionic additives commonly used in peptide separations, e.g., trifluoroacetic acid (TFA), complicating adsorption isotherm estimation. We investigated how the competition for available adsorption sites between TFA and two peptides influenced the adsorption isotherm in gradient elution. A model accounting for the competition with TFA was compared with a model neglecting TFA adsorption. We found that the two models predicted elution profiles with the same accuracy. We also found that the adsorption isotherms were extremely similar in shape, leading to the conclusion that neglecting the competition with TFA is a valid approximation enabling faster and more robust adsorption isotherm estimation for the studied type of sorbent.

  • 834.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Leśko, Marek
    Department of Chemical Engineering, Rzeszów University of Technology, Rzeszów, Poland.
    Enmark, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Kaczmarski, Krzysztof
    Department of Chemical Engineering, Rzeszów University of Technology, Rzeszów, Poland.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Fast estimation of adsorption isotherm parameters in gradient elution preparative liquid chromatography. I: The single component case2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1299, p. 64-70Article in journal (Refereed)
    Abstract [en]

    The inverse method is a numeric method for fast estimation of adsorption isotherm parameters directly from overloaded elution profiles. However, it has previously only been used for isocratic experiments. Here we will extend the inverse method so it can be used for gradient elution too. This extended inverse method will make it possible to study the adsorption of substances whose retention factor vary strongly with the mobile-phase composition, like peptides and proteins, where the classic methods will fail. Our extended inverse method was verified using both simulations and real experiments. For simulated overloaded elution profiles we were able to determine almost exact Langmuir adsorption isotherm parameters with the new approach. From real experimental data, bi-Langmuir adsorption parameters were estimated using both the perturbation peak method and the extended inverse method. The shape of the acquired adsorption isotherms did match over the considered concentration range; however, the adsorption isotherm parameters found with the two methods were not the same. This is probably due to the fact that adsorption isotherm estimated with the inverse method is only a good approximation up to the highest eluted concentration in the used chromatograms. But this is not a serious drawback from a process point of view where the main objective is to make accurate predictions of elution profiles. The bi-Langmuir adsorption isotherm obtained with both methods could accurately predict the shape of overloaded elution profiles.

  • 835.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Leśko, Marek
    Department of Chemical and Process Engineering, Rzeszów University of Technology.
    Enmark, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Kaczmarski, Krzysztof
    Department of Chemical and Process Engineering, Rzeszów University of Technology.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Fast estimation of adsorption isotherm parameters in gradient elution preparative liquid chromatography. II: The competitive case2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1314, no Nov, p. 70-76Article in journal (Refereed)
    Abstract [en]

    Abstract Experimental competitive adsorption isotherms were successfully determined directly from overloaded elution profiles in gradient elution mode using an extended inverse method. This approach differs from the existing methods in one important aspect – no isocratic experiments are necessary which makes it possible to study adsorption of substances whose retention factors vary strongly with the mobile-phase composition. The approach was verified with simulated binary data and with experimental data from gradient separations of a cyclohexanone/cycloheptanone mixture. For the synthetic data, the original adsorption isotherm parameters were found using a two-step estimation procedure. In the first step analytical peaks were used to estimate the “analytical” part of the Langmuir equation and in the second step the association equilibrium parameters were estimated from two simulated overloaded elution profiles. For the experimental data, a three-step approach was used. The two first steps were used to reduce the calculation time so that parameter estimation could be performed on an ordinary computer. In the first step, analytical peaks were used to estimate the “analytical” part of the bi-Langmuir equation. In the second step, initial guesses for all other parameters were determined separately for each solute using the faster Rouchon algorithm. In the final and third step, the more accurate orthogonal collocation on finite elements algorithm, was used to fine-tune the isotherm parameters. The model could accurately predict the shape of overloaded elution profiles. The shape of the adsorption isotherms agreed well with those determined with the standard isocratic method, although the numerical values were not the same. The extended inverse method is well suited for process optimization where few experiments and accurate predictions are important.

  • 836.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Leśko, Marek
    Department of Chemical Engineering, Rzeszów University of Technology, PL-35 959 Rzeszów, Poland.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Kaczmarski, Krzysztof
    Department of Chemical Engineering, Rzeszów University of Technology, PL-35 959 Rzeszów, Poland.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Method transfer from high-pressure liquid chromatography to ultra-high-pressure liquid chromatography. I. A thermodynamic perspective2014In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1362, p. 206-217Article in journal (Refereed)
    Abstract [en]

    This is the first investigation in a series that aims to enhance the scientific knowledge needed for reliable analytical method transfer between HPLC and UHPLC using the quality by design (QbD) framework. Here, we investigated the differences and similarities from a thermodynamic point of view between RP-LC separations conducted with 3.5 μm (HPLC) and 1.7 μm (UHPLC) C18 particles. Three different model solutes and one pharmaceutical compound were used: the uncharged cycloheptanone, the cationic benzyltriethylammonium chloride, the anionic sodium 2-naphatlene sulfonate and the pharmaceutical compound omeprazole, which was anionic at the studied pH. Adsorption data were determined for the four solutes at varying fractions of organic modifier and in gradient elution in both the HPLC and UHPLC system, respectively. From the adsorption data, the adsorption energy distribution of each compound was calculated and the adsorption isotherm model was estimated. We found that the adsorption energy distribution was similar, with only minor differences in degree of homogeneity, for HPLC and UHPLC stationary phases. The adsorption isotherm model did not change between HPLC and UHPLC, but the parameter values changed considerably especially for the ionic compounds. The dependence of the organic modifier followed the same trend in HPLC as in UHPLC. These results indicates that the adsorption mechanism of a solute is the same on HPLC and UHPLC stationary phases which simplifies design of a single analytical method applicable to both HPLC and UHPLC conditions within the QbD framework.

  • 837.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Leśko, Marek
    Rzeszów University of Technology, Poland.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Karlsson, Anders
    AstraZeneca R&D Gothenburg, Mölndal.
    Kaczmarski, Krzysztof
    Rzeszów University of Technology, Poland.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Combining Chemometric Models with Adsorption Isotherm Measurements to Study Omeprazole in RP-LC2016In: Chromatographia, ISSN 0009-5893, E-ISSN 1612-1112, Vol. 79, no 19, p. 1283-1291Article in journal (Refereed)
    Abstract [en]

    The adsorption of the proton-pump inhibitor omeprazole was investigated using RP-LC with chemometric models combined with adsorption isotherm modelling to study the effect of pH and type of organic modifier (i.e., acetonitrile or methanol). The chemometric approach revealed that omeprazole was tailing with methanol and fronting with acetonitrile along with increased fronting at higher pH. The increased fronting with higher pH for acetonitrile was explored using a pH-dependent adsorption isotherm model that was determined using the inverse method and it agreed well with the experimental data. The model indicated that the peaks exhibit more fronting at high pH due to a larger fraction of charged omeprazole molecules. This model could accurately predict the shape of elution profiles at arbitrary pH levels in the studied interval. Using a two-layer adsorption isotherm model, the difference between acetonitrile and methanol was studied at the lowest pH at which almost all omeprazole molecules are neutral. Omeprazole had adsorbate–adsorbate interactions that were similar in strength for the acetonitrile and methanol mobile phases, while the solute–adsorbent interactions were almost twice as strong with methanol. The difference in the relative strengths of these two interactions likely explains the different peak asymmetries (i.e., tailing/fronting) in methanol and acetonitrile. In conclusion, thermodynamic modelling can complement chemometric modeling in HPLC method development and increase the understanding of the separation.

  • 838.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Nilsson, Mikael
    Olsson, Susanne
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Svensson, Olof
    Klick, Silke
    Ennis, Julie
    Butterworth, Paul
    Watt, Denise
    Iliadou, Stavroula
    Karlsson, Angelica
    Walker, Joanne T.
    Arnot, Kate
    Ealer, Norb
    Hernqvist, Kerstin
    Svensson, Karin
    Grinell, Ali
    Quist, Per-Ola
    Karlsson, Anders
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    A quality control method enhancement concept: Continual improvement of regulatory approved QC methods2016In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 129, p. 273-281Article in journal (Refereed)
    Abstract [en]

    Quality Control methods (QC-methods) play an important role in the overall control strategy for drug manufacturing. However, efficient life-cycle management and continual improvement are hindered due to a variety of post-approval variation legislations across territories and a lack of harmonization of the requirements. As a result, many QC-methods fall behind the technical development. Developing the QC-method in accordance with the Quality by Design guidelines gives the possibility to do continual improvements inside the original Method Operable Design Region (MODR). However, often it is necessary to do changes outside the MODR, e.g. to incorporate new technology that was not available at the time the original method was development. Here, we present a method enhancement concept which allows minor adjustments, within the same measuring principle, outside the original MODR without interaction with regulatory agencies. The feasibility of the concept is illustrated by a case study of a QC-method based on HPLC, assumed to be developed before the introduction of UHPLC, where the switch from HPLC to UHPLC is necessary as a continual improvement strategy. The concept relies on the assumption that the System Suitability Test (SST) and failure modes are relevant for other conditions outside the MODR as well when the same measuring principle is used. It follows that it should be possible to move outside the MODR as long as the SST has passed. All minor modifications of the original, approved QC-method must be re-validated according to a template given in the original submission and a statistical equivalence should be shown between the original and modified QC-methods. To summarize, revalidation is handled within the pharmaceutical quality control system according to internal change control procedures, but without interaction with regulating agencies.

  • 839.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    A fundamental study of the impact of pressure on the adsorption mechanism in reversed-phase liquid chromatography2016In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1457, p. 97-106Article in journal (Refereed)
    Abstract [en]

    A fundamental investigation of the pressure effect on individual adsorption sites was undertaken based on adsorption energy distribution and adsorption isotherm measurements. For this purpose, we measured adsorption equilibrium data at pressures ranging from 100 to 1000 bar at constant flow and over a wide concentration range for three low-molecular-weight solutes, antipyrine, sodium 2-naphthalenesulfonate, and benzyltriethylammonium chloride, on an Eternity C18 stationary phase. The adsorption energy distribution was bimodal for all solutes, remaining clearly so at all pressures. The bi-Langmuir model best described the adsorption in these systems and two types of adsorption sites were identified, one with a low and another with a high energy of interaction. Evidence exists that the low-energy interactions occur at the interface between the mobile and stationary phases and that the high-energy interactions occur nearer the silica surface, deeper in the C18 layer. The contribution of each type of adsorption site to the retention factor was calculated and the change in solute molar volume from the mobile to stationary phase during the adsorption process was estimated for each type of site. The change in solute molar volume was 2-4 times larger at the high-energy site, likely because of the greater loss of solute solvation layer when penetrating deeper into the C18 layer. The association equilibrium constant increased with increasing pressure while the saturation capacity of the low-energy site remained almost unchanged. The observed increase in saturation capacity for the high-energy site did not affect the column loading capacity, which was almost identical at 50- and 950-bar pressure drops over the column. (C) 2016 Elsevier B.V. All rights reserved.

  • 840.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Lesko, Marek
    Department of Chemical and Process Engineering, Rzeszów University of Technology, PL-35 959 Rzeszów, Poland.
    Cavazzini, Alberto
    Department of Chemical and Pharmaceutical Sciences, University of Ferrara, IT-44 121 Ferrara, Italy.
    Kaczmarski, Krzysztof
    Department of Chemical and Process Engineering, Rzeszów University of Technology, PL-35 959 Rzeszów, Poland.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Method transfer from high-pressure liquid chromatography to ultra-high-pressure liquid chromatography. II. Temperature and pressure effects2015In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1401, p. 52-59Article in journal (Refereed)
    Abstract [en]

    The importance of the generated temperature and pressure gradients in ultra-high-pressure liquid chromatography (UHPLC) are investigated and compared to high-pressure liquid chromatography (HPLC). The drug Omeprazole, together with three other model compounds (with different chemical characteristics, namely uncharged, positively and negatively charged) were used. Calculations of the complete temperature profile in the column at UHPLC conditions showed, in our experiments, a temperature difference between the inlet and outlet of 16 degrees C and a difference of 2 degrees C between the column center and the wall. Through van't Hoff plots, this information was used to single out the decrease in retention factor (k) solely due to the temperature gradient. The uncharged solute was least affected by temperature with a decrease in k of about 5% while for charged solutes the effect was more pronounced, with k decreases up to 14%. A pressure increase of 500 bar gave roughly 5% increase in k for the uncharged solute, while omeprazole and the other two charged solutes gave about 25, 20 and 15% increases in k, respectively. The stochastic model of chromatography was applied to estimate the dependence of the average number of adsorption/desorption events (n) and the average time spent by a molecule in the stationary phase (tau(s)) on temperature and pressure on peak shape for the tailing, basic solute. Increasing the temperature yielded an increase in n and decrease in tau(s) which resulted in less skew at high temperatures. With increasing pressure, the stochastic modeling gave interesting results for the basic solute showing that the skew of the peak increased with pressure. The conclusion is that pressure effects are more pronounced for both retention and peak shape than the temperature effects for the polar or charged compounds in our study. (C) 2015 Elsevier B.V. All rights reserved.

  • 841.
    Åsberg, Dennis
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Weinmann, Annika Langborg
    AstraZeneca, Resp Inflammat & Autoimmun, Innovat Med & Early Dev Biotech Unit, SE-43183 Molndal, Sweden..
    Leek, Tomas
    AstraZeneca, Resp Inflammat & Autoimmun, Innovat Med & Early Dev Biotech Unit, SE-43183 Molndal, Sweden..
    Lewis, Richard J.
    AstraZeneca, Resp Inflammat & Autoimmun, Innovat Med & Early Dev Biotech Unit, SE-43183 Molndal, Sweden..
    Klarqvist, Magnus
    AstraZeneca, Resp Inflammat & Autoimmun, Innovat Med & Early Dev Biotech Unit, SE-43183 Molndal, Sweden..
    Lesko, Marek
    Rzeszow Univ Technol, Dept Chem & Proc Engn, PL-35959 Rzeszow, Poland..
    Kaczmarski, Krzysztof
    Rzeszow Univ Technol, Dept Chem & Proc Engn, PL-35959 Rzeszow, Poland..
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    The importance of ion-pairing in peptide purification by reversed-phase liquid chromatography2017In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1496, p. 80-91Article in journal (Refereed)
    Abstract [en]

    The adsorption mechanism for three peptides was studied under overloaded conditions through adsorption isotherm measurements in the presence of an ion-pairing reagent, trifluoroacetic acid (TFA), on an end-capped C18-bonded stationary phase. The overall aim of the study was to obtain a better understanding of how the acetonitrile and the TFA fractions in the eluent affected the overloaded elution profiles and the selectivity between peptides using mechanistic modelling and multivariate design of experiments. When studying the effect of TFA, direct evidence for ion pair formation between a peptide and TFA in acetonitrile-water solutions was provided by fluorine-proton nuclear Overhauser NMR enhancement experiments and the adsorption of TFA on the stationary phase was measured by frontal analysis. The adsorption isotherms for each peptide were then determined by the inverse method at eight TFA concentrations ranging from 2.6 mM to 37.3 mM (0.02–0.29 vol-%) in isocratic elution. The equilibrium between the peptide ion and the peptide-TFA complex was modelled by coupling the mass-balance to reaction kinetics and determining separate adsorption isotherms for the two species. We found that a Langmuir isotherm described the elution profile of peptide-TFA complex well while the peptide ion was described by a bi-Langmuir adsorption isotherm since it exhibited strong secondary interactions. The elution profiles had an unfavorable shape at low TFA concentrations consisting of a spike in their front and a long tailing rear due to the secondary interactions for the peptide ion having very low saturation capacity. The acetonitrile dependence on the adsorption isotherms was studied by determination of adsorption isotherms directly from elution profiles obtained in gradient elution which enabled a broad acetonitrile interval to be studied. Here, it was found that the column saturation capacity was quickly reached at very low acetonitrile fractions and that there were significant variations in adsorption with the molecular weight. Finally, practical implications for method development are discussed based on an experimental design where gradient slope and TFA concentrations are used as factors. (c) 2017 Published by Elsevier B.V.

  • 842.
    Östberg, Linda
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Kvarnlöf, Niklas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    The hemicellulose content in two chemical pulps and its influence on Fock´s test and the gamma number of the resulting viscose dope2013In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, no 3, p. 4p. 377-380Article in journal (Refereed)
14151617 801 - 842 of 842
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