Qualitative and semi-quantitative screening of selected psychoactive drugs in blood: Usefulness of liquid chromatography - triple quadrupole and quadrupole time-of-flight mass spectrometry in routine toxicological analyses

Abstract

Routine toxicological analysis requires broad screening for a large number of therapeutically prescribed and other compounds, and/or their metabolites. This article specifically focuses on three classes of psychoactive substances: antidepressants (ADs), antipsychotics (APs) and benzodiazepines and Z-drugs (BZDs). Two screening methods were compared for their ease-of-use in a routine setting, based upon the analysis of 105 medico-legal case samples. Analytes of interest were extracted using liquid-liquid extraction and separated using liquid chromatography with a total run time of 12 min per sample. A first detection method used targeted triple quadrupole mass spectrometry, operated in triggered multiple reaction monitoring mode (tMRM). False negative results were noted for 15% of the total number of detected analytes only, the majority of which were either present at sub- to low therapeutic levels or were metabolites of other analytes in the samples. The occurrence of false positive results was rare. A second screening method used quadrupole time-of-flight mass spectrometry (QTOF) for untargeted data acquisition. Data analysis was facilitated by the creation of an in-house, subset mass spectral database. As was seen for the tMRM screening, false negative results were observed in less than 20% of the total number of detected analytes, either for compounds at low concentrations or of which metabolites could be identified in the samples. More false positive results were observed due to an observed bias for prothipendyl. Determination of the exact concentration in a sample may only be required depending on the specific case circumstances. For this purpose, semi-quantification using each of the screening methods was investigated. Excellent results were observed using the tMRM method in combination with a small number of labelled internal standards (n = 12). Semi-quantification using the QTOF screening method was more laborious, but limited results on selected compounds indicated equally good results. Overall, the developed semi-quantitative screening methods performed well and - following further validation on case samples - could be implemented for most compounds in routine toxicological analysis without the need for highly trained or specialised personnel.

Keywords: Forensic toxicological screening; High-resolution mass spectrometry; Liquid chromatography; Psychoactive pharmaceuticals; Semi-quantification; Triggered multiple reaction monitoring.