Determination of clonazepam in human plasma by gas chromatography--negative ion chemical ionization mass spectrometry.

Our previously reported gas chromatographic--mass spectrometric assay for clonazepam using positive ion chemical ionization has been modified to employ negative ion chemical ionization. The sensitivity using this technique (less than 0.1 ng/ml) is approximately twenty times better than the positive ion chemical ionization procedure with similar precision. The method was used to determine the clonazepam plasma concentration in one human for 96 h following a single 2-mg dose of clonazepam.