Determination of drugs of abuse and metabolites in plasma microsamples by LC-MS/MS after microQuEChERS extraction

<b>Aim:</b> Identifying drugs of abuse and their metabolites in plasma is vital in both forensic and clinical toxicology. While the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method offers an efficient approach to sample preparation, its application is complex due to the wide-ranging properties of target analytes and the challenges posed by biological matrix interferences. This study aims to develop a microQuEChERS approach for the quantification of 14 drugs of abuse and metabolites utilizing minimal sample and solvent volumes.<b>Methods:</b> The microQuEChERS method involved using 10 μl plasma samples, 25 mg of a salt mixture and 150 μl of acetonitrile. Extracts were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), with a 7.5 min run. The assay was validated according to bioanalytical guidelines.<b>Results:</b> The accuracy was 96.8-112.4%. The within-assay precision was within 2.0-8.9% and the between-assay precision was within 3.2-8.2%. Matrix effects were found to range from -5.7 to 13.5%. The extraction yield was higher than 74.7%.<b>Conclusion:</b> This study described a microQuEChERS sample preparation approach for determining drugs of abuse and metabolites using plasma microsamples and LC-MS/MS. The approach is efficient, environmentally friendly and suitable for scenarios with limited amounts of biological samples.