High-performance liquid chromatographic determination of theophylline and its derivatives with electrochemical detection.

Theophylline and its derivatives are determined by high-performance liquid chromatographic separation on a C8 reversed-phase column with electrochemical detection. The analyte is oxidized at 1.24 V (vs. the standard calomel electrode) on a wax-impregnated graphite electrode using classical d.c. and current sampled d.c. modes, and the results obtained compared with those of a 254 nm ultraviolet (UV) detector. Polarographic detection offers greater sensitivity for theophylline than UV detection; further, interferences which hamper UV detection may be selectively eliminated with polarographic detection.