Owing to the ease and effectiveness of removing suspended substances (SSs), filtration has become a universal pretreatment step during water sample preparation. However, it can lead to the underestimation of contaminants if the targets easily associate with the SSs or filters. For the first time, this study comprehensively assessed issues related to filtration for the accurate quantification of 35 typical pharmaceuticals, including 28 antibiotics and seven non-steroidal anti-inflammatory drugs (NSAIDs), in water samples by comparing the effects of different filter materials, preservatives, and water matrices on the recoveries. The results showed that some sulfonamides and NSAIDs had an affinity for nylon filters, whereas trimethoprim and macrolides were easily retained on mixed cellulose ester filters. The use of glass fiber filter (0.7 μm) resulted in improved recovery of all the targets. Acidification promoted the adsorption of fluoroquinolones, tylosin, and roxithromycin on SSs, whereas 5% methanol resulted in desorption of macrolides from the SSs and other pharmaceuticals (sulfadiazine, trimethoprim, etc.) from the solid-phase extraction cartridges. Without additional detection of targets adsorbed on the SSs and filters, the addition of appropriate surrogates prior to filtration can help correct the loss.
Keywords: Filter materials; Multi-residue analysis; Pharmaceuticals; Preservatives; Water matrices.
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