Direct detection of the psychoactive substance MT-45 in human tissue samples by probe electrospray ionization-tandem...

Analyses of drugs and poisons in tissue samples are essential in forensic toxicology and pharmacology. However, current procedures for tissue analysis are laborious and time-consuming. Therefore, we assessed the utility of a newly devised probe electrospray ionization (PESI) technique with tandem mass spectrometry (MS/MS) for easy, ultra-rapid drug detection in human tissue samples. Using this system, typical pretreatment procedures, such as solid-phase extraction, liquid-liquid extraction, deproteinization, or homogenization, can be avoided. Briefly, a tissue sample of 1-2 mm³ was supplemented with a solution of ethanol and 10 mmol/L ammonium formate, and measurements were obtained. We demonstrated the successful application of this method in a forensic case by detecting an opioid analgesic, MT-45, in all tissue samples (liver, kidney, lung, brain, and heart). We also detected oxidized metabolites of MT-45 in the liver. Since the analysis required only 0.5 minutes per sample, PESI-MS/MS is an ultra-rapid detection method. Furthermore, for a quantitative approach, the total analysis time for the combination of PESI-MS/MS with the quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method (from instrument start-up to extraction and PESI-analysis) was within 8 minutes. MT-45 concentrations obtained by QuEChERS-PESI-MS/MS and liquid chromatography (LC) -MS/MS were similar for all tissue samples. PESI-MS/MS cannot be used to separate isobars/isomers (ie, compounds with the same m/z value), similar to other direct introduction techniques. Further studies are needed to validate the quantitation method. However, our results indicate that PESI-MS/MS is a potentially easy and rapid technique for the analysis of drugs and poisons in human tissue samples.