Application of ultra-sensitive GC-QqQ-MS/MS (MRM) method for the determination of diclofenac in whole blood samples without derivatization

Diclofenac is one of the most frequently prescribed nonsteroidal anti-inflammatory drugs (NSAID) worldwide. Although it is considered a relatively safe drug, it exhibits high toxicity to some animal populations (e.g., raptors). An ultra-sensitive gas chromatography method, coupled with tandem mass spectrometry (GC-QqQ-MS/MS) with an electron impact (EI) ionization source for diclofenac determination in whole blood samples without a derivatization procedure, was developed and fully validated. Diclofenac-d4 was used as an internal standard. The determination of analytes was performed in the multiple-reaction monitoring (MRM) mode. The method was linear in the range from 0.1 to 200 ng/mL, with a coefficient of determination of 0.999 (R2). The lower limit of quantification was 0.1 ng/mL, and the detection limit was 0.05 ng/mL. The blood samples (200 µL) were prepared by liquid–liquid extraction (pH3) with ethyl acetate. The intra- and interday accuracies and precisions did not exceed 15%. Recovery and matrix effect values were in the range of 92.2–105.9% and −7.8 to 5.9%, respectively. The developed method was applied in authentic blood samples. A simple and precise GC-QqQ-MS/MS method can be potentially applied for routine clinical, toxicological and environmental analysis.