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  • 1.
    Samuelsson, Jörgen
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Shalliker, R. Andrew
    Univ Western Sydney, Sch Sci & Hlth, Australian Ctr Res Separat Sci, North Parramatta, NSW 2751, Australia..
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Viscosity contrast effects in analytical scale chromatography: Evidence and impact2017In: Microchemical journal (Print), ISSN 0026-265X, E-ISSN 1095-9149, Vol. 130, p. 102-107Article in journal (Refereed)
    Abstract [en]

    The phenomenon known as viscous fingering has been shown to be very detrimental to separation performance in preparative and size exclusion chromatography, and also in multidimensional HPLC However, there are few reports of viscous fingering in analytical scale high performance liquid chromatography (HPLC), despite samples very often being introduced to the analytical-size HPLC columns in a solvent have a substantially different viscosity than the mobile phase. With this study we aim at first hand to investigate if viscous fingering or any similar and related effects to these in preparative levels also take place in analytical scale HPLC and if so, what impact this have on the separation performance. We could show that not only viscous finger does occur in analytical scale columns but also that peak distortions are apparent already at viscosity ratios between eluent and sample solution approaching unity. The latter indicates that a pre-viscous phenomenon is occurring that could be more important than the viscous fingering itself at the analytical format. As the viscosity contrast increases, the leading edge of the sample band distorts and the band volume increases, both leading to a decrease in performance.

  • 2. Vera, C. M.
    et al.
    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).
    Dennis, G. R.
    Shalliker, R. A.
    Protocol for the visualisation of axial temperature gradients in ultra high performance liquid chromatography using infrared cameras2018In: Microchemical journal (Print), ISSN 0026-265X, E-ISSN 1095-9149, Vol. 141, p. 141-147Article in journal (Refereed)
    Abstract [en]

    A protocol was developed for the visualisation of axial temperature gradients on a Kinetex column (1.3 μm C18 100 Å 50 × 2.1 mm) operated at near maximum pressure of the system (Pmax) using an infrared camera. Real time viscous frictional heating effects across the entire column length was observed, and showed that with increasing flow rate there was an increase in the maximum temperature of the column, and the difference between the inlet and outlet temperatures. Temperature profile data over the entire length of the column revealed the dynamics of heat exchange processes along different parts of the column, and raises the question on potential heating effects on eluents. The axial temperature gradients of eluents such as pure methanol, isopropyl alcohol and acetonitrile near Pmax were compared; finding that acetonitrile which had the highest flow velocity at Pmax gave the highest overall temperature increase for these eluents.

  • 3.
    Vera, C. M.
    et al.
    Western Sydney Univ, Australian.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. 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). Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Dennis, G. R.
    Western Sydney Univ, Australian.
    Shalliker, R. A.
    Western Sydney Univ, Australian.
    Visualisation of axial temperature gradients and heat transfer process of different solvent compositions in ultra high performance liquid chromatography using thermography2019In: Microchemical journal (Print), ISSN 0026-265X, E-ISSN 1095-9149, Vol. 145, p. 927-935Article in journal (Refereed)
    Abstract [en]

    Thermal imaging was used to visualise axial temperature gradients in chromatography columns running solvents of water, methanol and acetonitrile at various compositions. The non-monotonic relationship between solvent composition and viscosity enabled the testing of solvent conditions with equivalent viscosities, but with different percentages of water. It was observed that at equivalent power the increase in water composition leads to an increase in the magnitude of the axial temperature gradients (Delta T-A). Observing the change in temperature at defined points (Delta T-p) with increasing power indicates that the relationship between Delta T-p and power is not linear but deviates at higher power. The degree of this deviation depends on what point along the column axis is observed as well what solvent composition is used. Being able to monitor the entire length of the column using thermography also allowed for the observation of different rates of heat transfer through to the bulky stainless steel end fittings from solvent to solvent. Revealing that water is able to transfer heat to the stainless steel surface in such a way that the temperature profile of transition point between columns to end fitting is more gradual compared to when methanol or acetonitrile is used. This evidence plus video data collected indicates that at constant flow rate an equilibrium between heat generated and heat dissipated through the stainless steel is formed, which differs from solvent to solvent. Moreover any disruption to this equilibrium, i.e. a change in flow rate will momentarily change the shape of the temperature profile.

  • 4.
    Vera, C. M.
    et al.
    Phenomenex Australia Pty Ltd, Lane Cove, NSW 2067, Australia..
    Shock, D.
    Phenomenex Australia Pty Ltd, Lane Cove, NSW 2067, Australia..
    Dennis, G. R.
    Univ Western Sydney, Sch Sci & Hlth, Australian Ctr Res Separat Sci, Penrith, NSW 2751, Australia..
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Enmark, Martin
    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.
    Shalliker, R. A.
    Univ Western Sydney, Sch Sci & Hlth, Australian Ctr Res Separat Sci, Penrith, NSW 2751, Australia.
    Contrasting selectivity between HPLC and SFC using phenyl-type stationary phases: A study on linear polynuclear aromatic hydrocarbons2015In: Microchemical journal (Print), ISSN 0026-265X, E-ISSN 1095-9149, Vol. 119, p. 40-43Article in journal (Refereed)
    Abstract [en]

    A selectivity study was undertaken using two types of phenyl-type (Synergi polar RP and Cosmosil 5PBB) stationary phases in supercritical fluid chromatography. The mobile phases used in the SFC environment employed CO2 with methanol as the modifier. These columns were tested using linear polynuclear aromatic hydrocarbons as the test solutes. The retention behaviour of these PAHs in SFC was compared to their behaviour in HPLC and there were very distinct differences. On the Synergi-polar stationary phase the PAH selectivity was highly dependent on the methanol modifier concentration, but in comparison on the Cosmosil column, the selectivity between the members of this PAH test group showed almost no change as a function of the methanol concentration, even though the retentivity on the Cosmosil stationary phase was far greater than the Synergi stationary. In fact, the mobile phase played a very passive role in the separations observed on the Cosmosil stationary phase. (C) 2014 Elsevier B.V. All rights reserved.

  • 5.
    Vera, C. M.
    et al.
    Phenomenex Australia, Pty Ltd, Lane Cove, NSW 2067, Australia.
    Shock, D.
    Phenomenex Australia, Pty Ltd, Lane Cove, NSW 2067, Australia.
    Dennis, G. R.
    Australian Centre for Research on Separation Science, School of Science and Health, University of Western Sydney, Penrith, NSW 2751, Australia.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Enmark, Martin
    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.
    Shalliker, R. Andrew
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. Australian Centre for Research on Separation Science, School of Science and Health, University of Western Sydney, Penrith, NSW 2751, Australia.
    A preliminary study on the selectivity of linear polynuclear aromatic hydrocarbons in SFC using phenyl-type stationary phases2015In: Microchemical journal (Print), ISSN 0026-265X, E-ISSN 1095-9149, Vol. 121, p. 136-140Article in journal (Refereed)
    Abstract [en]

    The retention behaviour of a homologous series of polyaromatic hydrocarbons was evaluated on two phenyl-type stationary phases in reversed phase supercritical fluid chromatography (SFC). These phases were the Synergi polar-RP phase and the Cosmosil 5PBB phase, both of which are polar end-capped and incorporate an ether in a propyl chain that tethers the phenyl ring to the silica surface. The Cosmosil 5PBB phase also has five bromine atoms on the phenyl ring. The retention capacity of the Cosmosil column was substantially greater than the Synergi column. However, selectivity on the Cosmosil column was effectively independent of the acetonitrile modifier composition in the CO2 mobile phase, whereas, selectivity on the Synergi column was greatly affected by the acetonitrile modifier in the CO2 mobile phase. The results from this study showed that selectivity and retention studies in HPLC cannot be used to predict selectivity and retention behaviour in SFC. (C) 2015 Elsevier B.V. All rights reserved.

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