Quantitation of verapamil and norverapamil in postmortem and clinical samples using liquid-liquid extraction, solid phase extraction, and HPLC

Summary A sensitive micellar electrokinetic chromatography method for the determination of impurities in SB-209247, a novel LTB₄ antagonist, has been developed. Selectivity was optimised by systematic examination of the effects of the acetonitrile content in the separation buffer. Sensitivity and resolution was enhanced by focusing effects for both charged and neutral analytes achieved by a special sample buffer composition. Minor impurities well below 0.1% peak area ratio can be readily and reliably detected. The validity of the method has been successfully demonstrated with respect to reproducibility of peak area ratios and the linearity of a key impurity. A comparison with HPLC has shown the method has complementary selectivity and competitive sensitivity.