Multi-residue method for the analysis of pharmaceuticals and some of their metabolites in bivalves

• Analytical method for the simultaneous determination of pharmaceuticals and some major metabolites in mollusks.
• Fast, simple, robust, and easy to implement for routine analysis.
• Fifteen compounds detected over the MDL in oyster samples from shellfish farm in the Spanish Mediterranean.
• The antibiotic azithromycin has been detected for the first time in environmental samples of marine biota.

A fast, simple and robust method has been developed for the simultaneous determination of 23 pharmaceuticals (including some major metabolites) in bivalve mollusks. The analytes belong to eight different therapeutic groups: antibiotics, psychiatric drugs, analgesics/anti-inflammatories, tranquilizer, calcium channel blockers, diuretic, and prostatic hyperplasia. The method is based on pressurized liquid extraction (PLE) followed by solid phase extraction clean-up (SPE), and ultra performance liquid chromatography–triple quadrupole mass spectrometry (UHPL–MS/MS) for the identification and quantification of the target analytes. It has been developed and validated in three different species of bivalves: Crassostrea gigas (Pacific oyster), Mytilus galloprovincialis (Mediterranean mussel), and Chamelea gallina (striped venus clam). The majority of the compounds were extracted with a recovery between 40 and 115%. The developed analytical method allowed the determination of the compounds in the lower ng/g concentration levels. The relative standard deviation was under 12% for the intra-day and 20% inter-day analyses, respectively. Finally, the method was applied to oyster, clam and mussel samples collected from the Ebro delta, Spain. The most ubiquitous compounds detected were the psychiatric drug venlanfaxine and the antibiotic azithromycin, with the highest concentrations found in mussel (2.7 ng/g dw) and oyster (3.0 ng/g dw), respectively. To the best of our knowledge, this is the first time that azithromycin has been reported in environmental samples of marine biota.

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