An investigation of the stability of emerging new psychoactive substances.

The evolving nature of new psychoactive substances (NPS) - often referred to as 'legal highs', 'designer drugs' or 'bath salts' - presents an evolving challenge for toxicologists. Apart from the detection and identification of these compounds, further analytical challenges may arise from the presence of possible metabolites or degradation products which may have to be considered when devising an analytical strategy. Whilst there has been some stability research for some more established drugs of abuse and medicinal products, data on emerging NPS are less abundant. In order to address this need, 13 NPS (4-MEC, MDAI, methoxetamine, 5-MeO-DALT, 6-APB, MPA, 5-IAI, MDAT, 2-AI, AMT, 25C-NBOMe, AH-7921, 5-MAPB) were spiked in blood and plasma and kept at room temperature (20-23 °C). Detection and identification of the suspected breakdown products were carried out by high performance liquid chromatography with diode-array detection (HPLC-DAD), liquid chromatography-tandem mass spectrometry (LC-MS/MS), and ultra high performance liquid chromatography with high mass accuracy quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS). 4-MEC became undetectable in blood within 14 days with a corresponding loss of 54% in plasma. A breakdown product was identified as dihydro-4-MEC which was also found in vivo in a case work sample. Storage of AMT led to a range of potential breakdown products which were also found in vivo. The remaining substances were found to be stable for at least 21 days in blood and plasma. This is the first time stability data have been published for these emerging substances and showed that additional compounds found during forensic casework were potential metabolites rather than instability products. In particular, presumptive metabolites of 25C-NBOMe and AH-7921 are presented.