Highlights:

• The influence of changing %B (or tG), °C, and solvent type on selectivity is reexamined.
• These changes can be as effective as changing pH or column type when adjusting selectivity.
• These changes can mimic changes in pH, reducing or eliminating the need to optimize pH.
• Such continuous changes can be more effective than a step-wise change in column type

An older method for amlodipine was reworked with the goal to reduce the analysis time of 60min below 6min. To select the best column for short and robust analysis, 9 different UHPLC column chemistries were investigated using 3-dimensional resolution spaces based on 12 experiments using DryLab4 modelling software. The main variables used were gradient time (tG), temperature (T) and the pH of eluent A. The best critical resolution was calculated and located in a 3-dimensional space in an automated fashion and the corresponding best experiments were carried out. The work (9×12=108 runs) for DryLab4 modeling was finished with an UHPLC instrument in less than 24h. The comparison between predictions and real experiments showed an excellent correlation with differences typically less than 0.04min (<3s) in average, although the set points were located at quite different conditions on gradient times, pH's and temperatures for the individual columns. With the support of DryLab4 all columns could perform the required baseline separation at their individual best working points with satisfactory results.

An HPLC-UV method to determine compounds having a hydroxyl functional group in plant essential oils is developed. Separation conditions were optimized using the DryLab® method development software, a large sensitivity enhancement was obtained.

In this work, DryLab is used to accurately determine the design space for critical resolution in the analysis of water-soluble vitamins by HPLC. The multifactorial optimization of three measured parameters (gradient time, temperature, ternary eluent composition (B1/B2)) and seven calculated ones (flow rate, column length, column internal diameter, dwell volume, extracolumn volume, %B [start], and %B [end]) are illustrated. DryLab is used to examine multifactorial effects of these 3+7 parameters on critical resolution and selectivity. Multidimensional robust regions of high critical Rs were defined and graphically verified. The optimum method was selected based on the best resolution separation in the shortest run time. Predicted retention times of all peaks were found to be in excellent match with the virtual ones.

Highlights:

• Impurity profiling of a triple combination anti-HIV drug by SFC and RPLC is reported.
• Method development strategies and figures of merit with UV detection are discussed.
• A high degree of orthogonality was achieved with SFC.
• SFC also gave a more uniform distribution of components across the separation space.
• Potential impurities/degradation products were quantitated at the ≤0.1 area% level.

Highlights:

• Comparative study between column selectivity in RP-LC obtained for a real biomedical separation was reported.
• We performed classification of 24 RP-LC columns based on the QSRR approach.
• The reliability of the theoretical QSRR-model results was examined against column test performance based on the LC analysis of moclobemide and its two metabolites using two chemometric techniques.
• Principal component analysis (PCA) and hierarchical clustering analysis (HCA) were applied.