3-Dimensional Retention Modelling of Gradient Time, Ternary Solvent-Strength and Temperature of the Reversed-phase Gradient Liquid Chromatography of a Complex Mixture of 22 Basic and Neutral Analytes using DryLab® 2010 - Melvin R Euerbya, Gesa Sch

The present paper describes a multi-factorial optimization of three critical HPLC method parameters, i.e. gradient time (tG), temperature (T), and ternary composition (B1:B2) based on twelve experiments for the separation of twenty-two pharmaceutically relevant analytes. Examining the effect of these experimental variables on critical resolution and selectivity was carried out in such a way as to systematically vary all three factors simultaneously. The basic element is a gradient time–temperature (tG –T) plane, which is repeated at three different ternary compositions of eluent B between methanol and acetonitrile. The so-defined volume enables the investigation of the critical resolution for a part of the Design Space of a given sample. Multi-dimensional robust regions were successfully defined, graphically depicted and verified. The paper highlights the applicability of this approach for the rapid development of high quality robust LC methodologies.

Introduction
The use of Quality by Design (QbD) and Design Space (DS) principles [1] is becoming increasingly popular within the pharmaceutical environment. Regulatory authorities, including the Federal Drug Administration (FDA) and International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH), are actively promoting and demanding the application of these risk-based approaches to drug development in order to ensure a systematic approach in developing analytical methods.