Development of an achiral-chiral 2-dimensional heart-cutting platform for enhanced pharmaceutical impurity analysis

A new broadly applicable achiral-chiral 2-dimensional heart-cutting (LC-LC) platform is designed comprising a multi-column selection approach in the chiral dimension. As both dimensions are operated in a highly aqueous reversed-phase type mode, analysis of a broad range of pharmaceutical solutes (LogP: 1.49-5.7) and their impurities becomes possible, while breakthrough issues arising due to solvent immiscibility and peak broadening phenomena in the second dimension are practically circumvented. These aspects, together with the chromatographic and quantitative performances are systematically assessed for various transfer loop sizes (50, 100, 200 and 500 µl), column diameters (2.0 and 4.6 mm), and various gradients (10, 20 and 40 min) with a mixture of five racemates covering a broad range in polarity. In order to broaden the selectivity of the second dimension, an automated chiral screening is performed comprising six chiral columns, allowing baseline separation for all enantiomers and a chiral resolution up to 17.21 for some of the racemates. The performance of the platform is also assessed in pharmaceutical drug development samples. A hybrid high-resolution (HiRes) sample approach is thereby used, which proves to be effective for precise confirmation of the relative prevalence of the impurities compared to the principal compound in all studied cases. The co-eluted impurities were thereby effectively detected and quantified down to the 0.05% level. The obtained figures of merits indicate the suitability of the platform for implementation in industry.