Determination of peak homogeneity by dual detection

A general method has been elaborated to characterize peak homogeneity. The method uses two detection techniques and ratio formation of two simultaneou s signals, arising from the same detector cell section. The feasibility of the method is exemplified by the analysis of partially overlapping codeine- hydrocodone and completely overlapping codeine-oxycodone samples, where pea k homogeneity could be characterized by dual CD and UV detection. The S-CD/ S-UV ratio, and analogous ratios for other, coupled dual detection techniqu es, are proven to be concentration-independent intensive parameters of the analytes and can be used for identification purposes much more readily than retention times. The observed ratio clearly shows the pure section(s) of t he peak. Component composition can also be calculated in the case of hetero geneous peaks, and the ratio shows even the enantiomeric purity/impurity if achiral chromatography is hyphenated with dual (CD and UV) detection.