Integrated procedure for multiresidue analysis of dissolved and particulate drugs in municipal wastewater by liquid chromatography-tandem mass spectrometry.

For the first time, an integrated procedure for a quantitative multiresidue analysis of dissolved and particulate illicit drug target residues was developed and validated in three different wastewater matrices. The procedure consists of a comprehensive sample enrichment, fractionation and cleanup followed by the determination of target analytes by triple quadrupole liquid chromatography-tandem mass spectrometry in both positive and negative ionisation polarities. The enrichment of illicit drugs from suspended solids and aqueous samples was performed using pressurised liquid extraction and solid phase extraction (SPE), respectively. The performance of different SPE cartridges was investigated in order to optimise the overall recovery and to reduce the matrix effects. The optimal results were obtained by combining mixed cation exchange (Oasis MCX) cartridges for fractionated enrichment, weak anion exchange for an additional extract cleanup and optimised chromatographic separation to minimise the impact from co-extracted interferences. The method was applied for the analysis of raw wastewater (RW), activated sludge (AS) and secondary effluent (SE) samples collected at four different wastewater treatment plants. The average contributions of the particulate drugs in the RW and AS were 1-28 and 23-65 %, respectively. This suggested that the total mass loads of some drugs might be underestimated by neglecting the particulate fraction. Moreover, relatively high distribution coefficients, determined for 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (RW = 1211 L/kg) and 11-hydroxy-Δ(9)-tetrahydrocannabinol (RW = 1,786 L/kg) implied that adsorption might play a significant role in their overall removal during wastewater treatment.