In-silico optimised two-dimensional high performance liquid chromatographic (2D-HPLC) separations of a model methamphetamine seizure sample are described, where an excellentmatch between simulated and real separations was observed. DryLab optimisation reduced 2D-HPLC development time significantly. Targeted separation of model compounds was completed with significantly reduced method development time. This separation was completed in the heart-cutting mode of 2D-HPLC where C18 columns were used in both dimensions taking advantage of the selectivity difference of methanol and acetonitrile as the mobile phases. This method development protocol is most significant when optimising the separation of chemically similar chemical compounds as it eliminates potentially hours of trial and error injections to identify the optimised experimental conditions. After only four screening injections the gradient profile for both 2D-HPLC dimensions could be optimised via simulations, ensuring the baseline resolution of diastereomers (ephedrine and pseudoephedrine) in 9.7 min. Depending on which diastereomer is present the potential synthetic pathway can be categorised.

A new and fast ultra-high pressure liquid chromatographic separation of amlodipine and bisoprolol and all their closely related compounds is described for impurity profiling purposes. Computer-assisted method development with DryLab was applied and the impact of several state-of- the-art stationary phase column chemistries (50 × 2.1 mm, sub-2 μm, and core–shell type materials) on the achievable selectivity and resolution was investigated. The work was performed according to QbD-principles using design of experiment with three experimental factors: gradient time (tG), temperature (T), and mobile phase pH. DryLab proves that the separation of all compounds was feasible on numerous column chemistries within <10 min, by proper adjustments of variables. It was also demonstrated that the reliability of predictions was good, as the predicted retention times and resolutions were in good agreement with the experimental ones. The final, optimized method separates 16 peaks related to amlodipine and bisoprolol within 7 min, ensuring baseline separation between all peak-pairs.

The aim of this study was to apply quality-by-design principles to build in a more scientific and risk-based multifactorial strategy in the development of an ultrahigh-pressure liquid chromatography (UHPLC) method for omeprazole and its related impurities.

The work presents a quality-by-design–based method development strategy for a method that tests the purity of omeprazole. The scientific and risk-based multifactorial method development strategy uses visual chro- matographic modeling as a fast and easy-to-use development tool. To speed up the method development process, all experiments are performed on a UHPLC system. The final method is successfully transferred to HPLC conditions. Predicted and experimental retention times are verified to confirm accuracy of the model.

The goals in ultrahigh-pressure liquid chromatography (UHPLC) method development are to first find the best separation, second find the best column, and third find the most robust method in a multifactorial Design Space. Trial and error methods are not sufficient anymore and solid science based on Quality by Design (QbD) principles is required.

The goal of this study was to evaluate the accuracy of simulated robustness testing using commercial mod- elling software (DryLab) and state-of-the-art stationary phases. For this purpose, a mixture of amlodipine and its seven related impurities was analyzed on short narrow bore columns (50 × 2.1 mm, packed with sub-2  m particles) providing short analysis times. The performance of commercial modelling software for robustness testing was systematically compared to experimental measurements and DoE based pre- dictions. We have demonstrated that the reliability of predictions was good, since the predicted retention times and resolutions were in good agreement with the experimental ones at the edges of the design space. In average, the retention time relative errors were <1.0%, while the predicted critical resolution errors were comprised between 6.9 and 17.2%. Because the simulated robustness testing requires signif- icantly less experimental work than the DoE based predictions, we think that robustness could now be investigated in the early stage of method development.

Moreover, the column interchangeability, which is also an important part of robustness testing, was investigated considering five different C8 and C18 columns packed with sub-2  m particles. Again, thanks to modelling software, we proved that the separation was feasible on all columns within the same analysis time (less than 4 min), by proper adjustments of variables.