In-tip-fabric phase sorptive extraction (In-tip-FPSE): A proof of concept study for on-site and in-laboratory sample preparation of antidepressants and benzodiazepines

Abstract

In forensic toxicology, the accurate identification and quantification of drugs are essential for medico-legal investigations. However, the challenge of drug stability complicates this task. On-site extraction (OSE) offers a solution, eliminating the need for sample transportation and storage, reducing degradation risks, and enhancing time, cost, and data quality. In the present work, we propose an innovative approach: In-tip-fabric phase sorptive extraction (In-tip-FPSE), designed for both on-site and in-laboratory sample preparation of antidepressants (ADs) and benzodiazepines (BZDs) from urine and postmortem blood samples. Initially, a sol–gel Carbowax 20 M (CW20M) coated FPSE membrane was prepared using unbleached cotton as the fabric substrate. For the fabrication of the In-tip-FPSE device, two cleaned FPSE membranes (1 cm × 1.5 cm) were positioned inside a 1 mL micropipette tip and fitted into a standard micropipette. The extraction procedure involves repeated aspirating/dispensing cycles (40 times) of the diluted samples within the micropipette tip to facilitate efficient extraction onto the FPSE membrane. Subsequently, elution is achieved by aspirating 1 mL of methanol (MeOH), followed by vertical positioning of the micropipette for 10 min, after which the eluted MeOH is dispensed into a GC–MS vial for analysis. Optimization of the In-tip-FPSE procedure involved exploring parameters such as the type and size of membrane, number of aspirating/dispensing cycles, type and volume of elution solvent, sample pH, and ionic strength. Under optimized conditions, the limit of quantification (LOQ) ranged from 33-41 µg/L and 42–49 µg/L for urine and blood, respectively. The relative standard deviation for intra and inter-day precision was less than 4 % and 10 %, respectively. The method exhibited excellent linearity in the range of 5–5000 µg/L for both matrices with a coefficient of determination (R2) in the range of 0.998 – 0.999. Absolute recovery (AR%) values for this method in real samples ranged from 85%-110 %. Furthermore, the practicality, greenness, and sustainability of the In-tip-FPSE method were assessed, demonstrating its superiority over previously reported in-laboratory methods. Finally, the method was successfully applied for OSE of target analytes from urine samples and in-laboratory analysis of postmortem blood samples.