A method for the simple and reliable determination of triazolam and midazolam in human plasma using gas chromatography with microelectron capture detection has been developed. Samples (0.5 mL of plasma) were prepared using a simple solvent extraction with 3% isoamyl alcohol/benzene in the presence of NaOH. Two microlitres of the extract were injected onto the capillary column ((5%-phenyl)-methylpolysiloxane). The method was found to be valid in terms of selectivity, linearity, precision, accuracy, and recovery over the concentration range of 0.2 to 20 ng/mL for triazolam, and from 0.5 to 200 ng/mL for midazolam, respectively. Intra- and inter-day precisions determined at three concentrations were from 4.1 to 9.3% for triazolam and from 2.9 to 13.0% for midazolam. The accuracies were within 17.7% for triazolam and within 13.0% for midazolam. This proposed method was successfully applied to a pharmacokinetic study of triazolam or midazolam in healthy volunteers.
