Measurement of clonazepam by electron-capture gas-liquid chromatography with application to single-dose...

A simple, sensitive, and rapid method for analysis of clonazepam in blood by gas-liquid chromatography with electron-capture detection is described. The method employs neutral benzene extraction from plasma and concentration into a small volume for autoinjection into the electron capture detector-equipped chromatograph. This method consistently provides blank plasma samples free of contaminants in the areas corresponding to the retention times for clonazepam and desmethylflunitrazepam (the internal standard). Sensitivity is 1 ng/mL, and standard curves are linear from 1 to 200 ng/mL. The applicability of the method to single-dose pharmacokinetics is illustrated.