Ultrasound assisted membrane-assisted solvent extraction for the determination of antidepressants in pericardial fluid by gas chromatography-mass spectrometry

• MASE has been used for the first time to determine ATDs in pericardial fluid. • Use of pericardial fluid as a complementary sample to blood. • A sensitive method is needed to detect low concentrations present in biological samples. The current trend in the development of analytical methods focuses on the miniaturization of sample preparation techniques, avoiding the consumption of large volumes of organic solvents and replacing the more harmful ones with less toxic solvents. In order to bring Forensic Toxicology closer to this trend, a simple method based on membrane-assisted solvent extraction (MASE) has been developed for the first time for the determination of three antidepressants (ATDs) using pericardial fluid as an alternative biological sample to blood. The analytes under study were later determined by gas chromatography-mass spectrometry (GC–MS). The optimized extraction procedure consisted of using 400 µL of n-hexane as an extractant solvent, placed inside a polypropylene (PP) membrane, and 4 mL of pericardial fluid (pH adjusted at 11). Ultrasound assistance (50–60 Hz, room temperature, 30 min) was used to favor analytes mass transfer from the aqueous phase to the organic phase. The n-hexane extract was further evaporated to dryness and reconstituted with 40 µL of methanol, achieving a preconcentration factor of 100. Validation was performed in accordance with FDA guidance as a reference. Lower limit of quantification (LOQ) values of 5 ng/mg were achieved for each ATD under study. The recoveries were higher than 90 % and the values of accuracy and precision did not exceed the maximum allowed error of 20 % for the LOQ or 15 % for the remaining concentration levels. Finally, the method was successfully applied to 14 real cases.