Pitfalls and Prevention Strategies for Liquid Chromatography–Tandem Mass Spectrometry in the Selected Reaction Monitoring Mode for Drug Analysis

sults with the use of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Differ-ent LC-MS/MS techniques that use the selected reac-tion–monitoring mode, routinely employed for the analysis and quantification of drugs and toxic com-pounds in biological matrices, were involved in the false-positive and potentially false-positive results ob-tained. We sought to analyze the causes of and solu-tions to this problem. METHODS: We used a previously reported LC-MS/MS general unknown screening method to perform verifi-cation and identification of interfering compounds. RESULTS: We observed that the cases involving false-positive results involved a metabolite of zolpidem that might have been mistaken for lysergic acid diethylam