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

Abstract

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.

Advances in Ionization for Mass Spectrometry

“…Addition of an in-vacuum plasma ionization source minimized ion transfer loss in the continuous atmospheric pressure interface. Another interesting coupling of techniques came from Famiglini et al These authors highlighted a direct interface of electron ionization (EI) with LC for direct flow injection-MS/MS of small molecules in alcoholic beverages. Benham et al coupled laser-induced acoustic desorption (LIAD) with APPI and demonstrated its utility by analyzing a number of low-polarity organics .…”

Evaluation of a liquid electron ionization liquid chromatography–mass spectrometry interface

“…Direct-EI was successfully used in a variety of applications [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] in a range of fields of research, demonstrating the lack of matrix effects [39][40][41]. It is not influenced by the co-elution of analytes or matrix components, making it highly suitable for direct introduction of diluted samples without chromatographic separations [37] or paired with a condensed-phase membrane introduction mass spectrometry (CP-MIMS) for real time monitoring of aqueous solutions [38] through a direct analysis of co-permeating compounds. Direct-EI has been successfully used by Zimmermann and coworkers [42,43] with direct infusion resonanceenhanced multiphoton ionization (DI-REMPI) and in combination with single photon ionization (SPI) for hard and soft ionization.…”

Current developments in LC-MS for pharmaceutical analysis

“…Both for the direct flow injection analysis of 16 polyaromatic hydrocarbons (PAHs) and the Direct-EI-LC-MS analysis of four hormones, peaks obtained with a ceramic coated ion source were much sharper and displayed significantly higher signal-to-noise (S/N) ratios (up to a four-fold increase) compared to a stainless-steel ion source. The application of the Direct-EI LC interface in combination with MS/MS was also demonstrated for the targeted detection and quantification of benzodiazepines in alcoholic drinks 29 . For this purpose, a fast direct-injection method requiring no prior sample preparation was proposed and validated, resulting in detection limits (LOQ) between 100 and 500 µg/L when injecting 2 µL of sample.…”