Multiple absorbance ratio correlation — a new approach for assessing peak purity in liquid chromatography

Abstract The theory of multiple absorbance ratio correlation (MARC), a novel method for examining chromatographic peaks, is presented. The MARC hypothesis provides a method for examining chromatographic peaks for homogeneity, identity and purity, operating on multi-wavelength data sets which do not contain full spectra. Paraxanthine (PX) is an endogenous caffeine metabolite which is spectrally similar (r 0.99) to theophylline (TH) and which often coelutes with it. Multi-wavelength data, collected using an HP1040A diode-array detector, for a series of binary mixtures of TH and PX (0.7 R s