Abstract

The combination of chromatography and mass spectrometry is the golden standard in forensic sciences. Although this approach provides high sensitivity and selectivity levels, it is time-consuming. The circumvention of the chromatography can increase the sample throughput, but the selectivity must be compensated by using a selectivity enhanced instrumental technique, such as high-resolution mass spectrometry (HRMS), and designing an appropriate sample preparation step. Microextraction by packed sorbent (MEPS) has proven potential to treat complex biological samples in a fast and reproducible way. It allows processing low sample volumes, remaining a green procedure due to low solvent consumption. This article presents the direct coupling of a MEPS syringe to the electrospray ionization source (ESI) of a quadrupole time-of-flight mass spectrometer (QqTOF) using an infusion pump for sample introduction, as a proof of concept. The developed method was validated for the simultaneous analysis of benzodiazepines and tricyclic antidepressants in postmortem blood samples. Limits of quantification (LOQ) were between 25 and 50 ng mL-1 for all compounds. Accuracy and precision were evaluated at three concentration levels (50, 125 and 350 ng mL-1) and expressed in terms of relative error (%RE) and relative standard deviation (%RSD), respectively. Both parameters were better than 20% for the lower concentration evaluated and better than 15% for the other two concentration levels. The developed method was used to analyze authentic postmortem blood samples, to test the applicability in the forensic toxicological context. The results are in agreement with the data provided by the medico-legal services. Also, the application of HRMS has allowed the identification of unexpected targets in the samples.