Rapid detection and quantification of 35 benzodiazepines in urine by GC-TOF-MS

A rapid and sensitive method for the screening and quantification of 35 benzodiazepines in human urine by gas chromatography/time-of-flight mass spectrometry was developed and validated. Target analytes were isolated from 1 ml urine by solid-phase extraction using Oasis MCX extraction columns (extraction recovery between 35 and 99 %). With a supported liquid-liquid extraction method, a new modification of conventional liquid-liquid-extraction, a less time intensive alternative for benzodiazepine extraction is presented. The sample pretreatment entails the derivatization of the benzodiazepines with N,O-bis(trimethylsilyl)trifluoroacetamide plus 1 % trimethylchlorosilane. Separation of all benzodiazepines was done within 9.5 min, and detection was based on full mass spectra for each analyte. A deconvolution algorithm was used for unresolved chromatographic peaks to identify coeluted substances. The subsequent quantification was done using significant masses. The limit of quantification is 10 ng/ml for most of the compounds. Linearity is in the range between 10 and 350 ng/ml. Reproducibility was observed with coefficients of variation below 2 % at concentrations of 50 and 200 ng/ml. The accuracy is between 88 and 108 % depending on the respective analyte and the concentration.