Analysis of acidic, basic and neutral pharmaceuticals in river waters: clean-up by 1°, 2° amino anion exchange and enrichment using an hydrophilic adsorbent

A fast and sensitive LC-MS/MS method suitable to monitor a set of 24 pharmaceuticals belonging to 9 therapeutical families was developed using an analytical column of reduced dimensions and an appropriate SPE procedure for acidic, basic and neutral analytes. Furthermore, a preliminary assessment of the occurrence and levels of these substances in surface waters of the Leca and Douro rivers, located in the north of Portugal, was conducted. Among 17 different SPE adsorbents tested, some of them often neglected, the JTBaker H2Ophilic provided the best recoveries (average 86%). When compared to the amino and quaternary ammonium adsorbents, the 1°, 2° amino proved the most suitable clean-up media for surface water samples prior to enrichment by SPE. The overall method provided limits of detection generally below 5 ng L−1 and a precision below or around 10% RSD in three non-consecutive days at 500 ng L−1 and around 12% at 50 ng L−1 concentration levels. The confirmatory capabilities of the method developed are ...