Liquid chromatography-electron ionization tandem mass spectrometry with the Direct-EI interface in the fast determination of diazepam and flunitrazepam in alcoholic beverages

This is the first application based on electron ionization (EI) using a Direct-EI LC interface and MS/MS to detect unequivocally target compounds in a very small real sample. The determination and quantification of benzodiazepines in very small residues of beverages, collected at the scene of drug-facilitated crimes are mandatory in legal procedures. A specific and sensitive analytical instrumentation is needed, involving little or no sample preparation. Here, a direct flow injection analysis of alcoholic beverages spiked with commercially available drugs containing diazepam and flunitrazepam is presented. The method proposed is very fast and requires neither sample preparation nor chromatographic separation. Linearity (R(2) ) was between 0.9977 and 0.9992; LOD and LOQ spanned from 0.01 to 0.02 ng/μL and from 0.1 to 0.5 ng/μL, respectively; intra- and interday repeatabilities were between 1 and 8%. No matrix effects were observed from the comparison of the linear regression curves obtained in real fortified samples and in pure ethanol. Vodka, whisky, and white wine specimens were fortified with commercial drugs, Valium(®) and Rohypnol(®) , at two different concentrations (20 and 50 ng/μL) to simulate the typical amounts found in adulterated real samples and analyzed to demonstrate the method applicability to forensic analyses.