Simultaneous analysis of opioid analgesics and their metabolites in municipal wastewaters and river water by liquid chromatography-tandem mass spectrometry

Although published literature provides a clear demonstration of widespread occurrence of opioid analgesics (OAs) in the aquatic environment, analytical methods suitable for a systematic study of this pharmaceutical class, which would include a broad spectrum of opioid analgesics and their metabolites, are still missing. In this work, a comprehensive multiresidue method for quantitative analysis of 27 opioid analgesics and their metabolites, including 2 morphine glucuronide conjugates, was developed and validated for three matrices: raw wastewater (RW), secondary effluent (SE) and river water. The method comprised different classes of opioid analgesics, including natural opiates (morphine and codeine), their semi-synthetic derivatives (hydrocodone, hydromorphone, oxycodone, oxymorphone and buprenorphine) as well as fully synthetic opioids such as methadone, fentanyl, sufentanil, propoxyphene and tramadol. The optimized enrichment procedure involved mixed-mode, strong cation-exchange sorbent in combination with a sequential elution procedure. The extracts were analyzed by reversed-phase liquid chromatography using a Synergy Polar column coupled to electrospray ionization tandem mass spectrometry (LC-MS/MS). Accurate quantification of target OAs was achieved using 19 deuterated analogues as surrogate standards. Method accuracies for RW, SE and river water varied in the range from 91 to 126%, 74 to 120% and 75 to 116%, respectively. Careful optimization of the procedure allowed reliable determination of OAs with method quantification limits in the low ng/L range (RW: 0.3-3.5 ng/L; SE: 0.2-1.9 ng/L, river water: 0.1-0.8 ng/L. The developed method was applied for analysis of RW, SE and river water samples from Croatia. The concentrations of individual OAs in municipal wastewater varied in a wide range (from < QL to 859 ng/L) and the most prevalent representatives were tramadol, codeine, morphine and methadone and their derivatives. Elevated concentrations of morphine glucuronides (up to 370 ng/L) found in raw municipal wastewater indicated their importance in the overall morphine mass balance.