Quantitative gas chromatographic analysis of flunitrazepam in human serum with electron-capture detection

A rapid method for the determination of flunitrazepam and desmethylfflunitrazepam in human serum in the range 10-300 ng/ml is described. Both drugs are isolated from biological material by means of a single extraction, part of the organic phase is evaporated to dryness and the residue is dissolved in a small volume of benzene. Without further purification, the substance is determined gas chromatographically with an electron-capture detector configuration of 63Ni-type. The method permits the quantitative determination of at least 25-300 ng/ml with an overall recovery of flunitrazepam of 99.7 +/- 4.9% and of desmethylflunitrazepam of 98.6 +/- 7.8% from serum. All calculations were carried out by a data system that was programmed for this purpose. The limit of detection for flunitrazepam is of the order of 1 ng/ml in serum. The method is sufficiently sensitive and specific for therapy control purposes. The time needed for an analysis is less than 1 h.