The In Vitro Stability of Four New Psychoactive Substances in Urine Samples Stored At Different Temperatures

Objective: In the last ten years New Psychoactive Substances (NPS) have become more frequent than the classic illicit drugs. The stability of these compounds during the different storage temperatures is less known, so the aim of our study was to investigate the extent of in vitro degradation in urine samples stored at room temperature (25 °C), in the refrigerator (4 °C) and in the freezer (-20 °C) for 21 days. Methods: The analysis was performed on HPLC-DAD system. The confirmatory examination of synthetic cannabinoid parent compounds was carried out on SFC-MS/MS. Results: N-Ethyl-Pentylone was stable at all three storage temperature. N-ethyl-hexedrone shows a significant (p = 0.03) decrease at room temperature, but was stable in the refrigerator and in the freezer. 5F-MDMB-PINACA and ABFUBINACA metabolites seemed stable at lower temperatures, but at 25 °C the degradation was significant (p = 0.04). Conclusion: The temperature greatly influences the stability, so based on our measures we conclude that the storage exclusively at -20 °C is satisfactory for the majority of NPS.