Matrix effects on mass spectrometric determinations of four pharmaceuticals and personal care products in water, sediments, and biota

Abstract

Simple analytical methods were developed for the extraction and determination of four pharmaceuticals and personal care products (PPCPs) from water, sediments, and biota. PPCPs were determined using tandem LC-MS in electrospray ionization mode, and interactions with matrix co-eluents were investigated. Extractions of water samples were performed using solid-phase extraction (SPE), sediments were extracted by pressurized liquid extraction (PLE), and biota was extracted by liquid extraction. The selected analytical methods yielded recoveries 61% in all matrixes. Matrix interactions were investigated throughout the linear range of quantification of each compound, revealing that dissolved salts had relatively minor effects on ionization (between 14% suppression to 12% enhancement), but that sediment and biota extracts caused significant matrix effects (ranging from 56% suppression to 25% enhancement). The direction and magnitude of matrix interactions reflected the physico-chemical properties of each analyte, particularly their pKa. Among the compounds analyzed in electrospray positive mode, carbamazepine was insensitive to matrix interactions, because it is a strong proton acceptor (pK a = 14.0). In contrast, atorvastatin (pK a = 4.5), a weaker proton acceptor, was particularly sensitive to matrix effects. For those compounds analyzed in negative-ion mode, sample alkalinity was found to be important. With a pK a of 10.4, 17a-ethinylestradiol generally exhibited matrix enhancement with increased sample alkalinity. However, the presence of acidic co-eluents contributed to matrix suppression. Lastly, TCS was particularly sensitive to matrix suppression, as its circumneutral pK a (7.9) caused even slight changes in sample pH to considerably impact ionization. We conclude that while different matrixes have clear impacts on ionization of these PPCPs, matrix effects can be quantified and overcome.Key words: pharmaceuticals and personal care products, matrix effects, LC-MS/MS, sediments, biota. Résumé :On a développé des méthodes analytiques simples pour l'extraction et la détermination de quatre produits pharmaceutiques et de soins personnels (PPSP) à partir de solutions aqueuses, de sédiments et du biote. On a déterminé les PPSP en faisant appel à la chromatographie liquide opérant en tandem avec spectrométrie de masse en mode d'ionisation par électronébulisation (CL-SM) et on a étudié les interactions avec les coéluants de la matrice. Les extractions à partir de solutions aqueuses ont été effectuées en utilisant l'extraction en phase solide (EPS) alors que les sédiments ont été soumis à une extraction avec un liquide pressurisé (ELP) et que le biote a été soumis à une extraction liquide. Dans l'ensemble des matrices, les méthodes analytiques choisies ont permis d'obtenir des taux de récupération d'au moins 61 %. On a étu-dié les interactions avec la matrice pour la plage entière de quantification de chaque composé et ces études ont révélé que les sels dissous n'ont que des effets mineurs sur l'ionisation (alla...

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