Determination of antihypertensive and anti-ulcer agents from surface water with solid-phase extraction-liquid chromatography-electrospray ionization tandem mass spectrometry.

Pharmaceuticals are emerging contaminants in surface water and they must be measured to follow their effects on the aquatic environment. We developed a solid-phase extraction and liquid chromatography-electrospray ionization tandem mass spectrometry (SPE-LC-ESI-MS/MS) method for the determination of twenty-six pharmaceutical compounds - which belong to antihypertensive and anti-ulcer agents - from surface water samples. The selection of pharmaceuticals was based on usage frequency in Hungary. During method development Oasis HLB, SampliQ Polymer SCX and Si-SCX SPE cartridges were tested. As LC eluent ammonium formate, ammonium acetate buffers at pH 3 and 5 were investigated and for quantitation both matrix-matched and internal standard calibration was used. For matrix effect assessment post-extraction spike method was applied which can separate the extraction efficiency from ion suppression for better determination of recovery. Method detection limits (MDLs) varied between 0.2 and 10 ng/L. Precision of the method, calculated as relative standard deviation (RSD), ranged from 0.2 to 14.6% and from 1.2 to 22.4% for intra- and inter-day analysis, respectively. The method was applied to analyze Danube water samples. Measured average concentrations varied between 2 and 39 ng/L for eleven compounds and another one could be detected under LOQ.