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.

Ultra-high performance liquid chromatography (UHPLC) provides a considerable increase in throughput compared to conventional HPLC and a reduced solvent consumption. The implementation of UHPLC in pharmaceutical analysis has accelerated in recent years and currently both instruments are used. 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. In UHPLC, the column is packed with smaller particles than in HPLC resulting in higher pressure and viscous heating. Both the higher pressure and the higher temperature may cause changes in retention and selectivity making method conversion unpredictable.

Using chromatographic modelling and fundamental theory, this thesis investigates 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 quality control methods and how predicable method conversion is achieved by improved understanding.