Mixed-Mode Gradient HPLC Analysis of a Tyrosine Kinase Inhibitor, Its Isomers and Other Potential Impurities

A mixed-mode high performance liquid chromatographic (HPLC) method has been developed for the determination of RG-14620 and its potential impurities and degradation products in a topical formulation. The separation of geometric and other structural isomers of RG-14620 as well as potential process impurities and degradation products was achieved by gradient elution from a Supelcosil LC-SCX cation exchange column (5 urn particle size, 250 × 4.6 mm i.d.) in series with a Nova-Pak dimethyloctadecylsilyl analytical column (4 μm particle size, 150 × 3.9 mm i.d.). The gradient components were 25mM sodium phosphate buffer (pH=3.5) and acetonitrile. The flow rate was 1.1 mL/min. with UV absorbance detection at 260 nm. The implementation of the mixed-mode technique is especially useful for pharmaceutical products whose collective mixture of precursors and potential degradation products often span a wide range on the polarity scale.