High concentrations of nordiazepam may impair the detection of benzoylecgonine by GC-MS with derivatization

Costa, Suzel; Rosendo, Luana M.; Barroso, Mário; Gallardo, Eugenia

http://hdl.handle.net/10400.26/54091

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Introduction: Forensic toxicology plays a pivotal role in legal investigations, particularly in detecting substances in biological samples. However, the simultaneous presence of multiple substances can pose analytical challenges. For instance, nordiazepam, a major metabolite of some benzodiazepines, can interfere with the detection of benzoylecgonine, a primary metabolite of cocaine, when using gas chromatography-mass spectrometry (GC-MS) with N- methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA) derivatization. This interference could result in false negatives for benzoylecgonine detection. Aims: This study aims to assess whether N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MBDSTFA) derivatization can reduce interference from nordiazepam, thereby improving the detection and quantification of benzoylecgonine in biological samples. Methods: Solid phase extraction (SPE) was carried out on post-mortem blood samples using Oasis® MCX columns. Microwave derivatization with MSTFA or MBDSTFA followed after the extracts were evaporated. Results and discussion: Two derivatization reagents, MSTFA and MBDSTFA, were compared using GC-MS to evaluate their effectiveness. For this assessment, both the limit of detection (LOD) and limit of quantification (LOQ) for benzoylecgonine in this chromatographic method were 10 and 25 ng/mL, respectively. MBDSTFA derivatization significantly reduced analytical interference between nordiazepam and benzoylecgonine. In contrast, MSTFA derivatization resulted in substantial interference at high concentrations of nordiazepam, potentially leading to false negatives for cocaine detection. These findings highlight the superior performance of MBDSTFA in complex toxicological analyses. Conclusion: MBDSTFA derivatization is more effective than MSTFA for minimizing interference in the detection of benzoylecgonine in the presence of nordiazepam. This method enhances the specificity of forensic toxicological analyses and helps prevent false negatives for detecting cocaine consumption through its principal metabolite, thereby supporting more reliable legal and clinical decisions.