Improved gas chromatographic procedure for the determination of clonazepam levels in plasma using a nitrogen-sensitive detector

A gas-liquid chromatographic procedure (GLC) is described for the determination of clonazepam in plasma. The drug is extracted from buffered plasma at pH 9.0 with diethyl ether and then back-extracted into 6 N hydrochloric acid-6N sulfuric acid (95:5) and hydrolyzed at 100 degrees C to convert the drug into its benzophenone derivative. The benzophenone derivative of flurazepam is added to plasma as an internal reference standard. Drug derivatives are finally extracted from the neutralized aqueous phase and assayed by GLC. The present procedure makes use of a nitrogen-sensitive detector which is more stable and selective than the commonly employed electron-capture procedure. The sensitivity of the detector for clonazepam is 1 ng/ml.