ESTIMATION OF THE ANALGESIC MUSCLE-RELAXANTS CHLORZOXAZONE AND DIAZEPAM IN HUMAN PLASMA BY REVERSED-PHASE LIQUID-CHROMATOGRAPHY

A rapid and sensitive method of extraction of human plasma containing acetaminophen, chlorzoxazone, oxyphenbutazone and diazepam along with their active metabolites was developed. The plasma samples were extracted by a solid-phase extraction procedure with theophylline as an internal standard for accurate quantitation. The reversed-phase liquid chromatographic method provided a linear ultraviolet detector response in the range 100.0-700.0 ng/ml. Recoveries greater than 95% were achieved from human plasma samples. Limits of detection of 100, 200, 150 and 250 ng/ml for acetaminophen, chlorzoxazone, oxyphenbutazone and diazepam, respectively, were obtained. © 1990.