Study of pharmaceutical determination in water by solid phase extraction followed by liquid chromatography-mass spectrometry

Abstract

An analytical method has been studied for the determination of selected pharmaceuticals in different water samples by liquid chromatography coupled to tandem mass spectrometry (LCMS/MS). Samples studied were 9 in total from different types(two surface water, three effluents and four influents wastewater) coming from various locations in Spain. The studied pharmaceuticals included eight antibiotics, an analgesic, an antidepressant, a hypolipidemic agent, two antihypertensive, an antiepileptic, an anti-inflammatory, and one anthelmintic agent. The study consisted in the investigation of the quality control (QCs) prepared from selected samples fortified at 500 ng/mL for surface an effluent wastewater and 100 ng/mL for influent wastewater. A prior solid phase extraction (SPE) was performed using Oasis HLB (150 mg) cartridges. The corresponding isotopically- labelled internal standards (ILIS) were added before extraction. The analytical determination was performed by LC-MS/MS using a triple quadrupole analyser and three MS/MS transitions were acquired for each analyte for a reliable confirmation. The matrix effect was evaluated from the experiences performed by ILIS. The results were satisfactory for the surface water samples, for the rest of the samples this effect was higher. The extraction process was evaluated in terms of accuracy and precision using the corresponding ILIS for correction. Recoveries of the 16 selected pharmaceuticals were in general satisfactory (between 70-120%) for all types of water samples studied, with the exceptions of some drugs in effluent wastewater such as Trimethoprim, with results higher in influent wastewater for instance: Norfloxacin, Ciprofloxacin and Acetaminophen. Relative standard deviations (RSDs) were lower than 20% for the majority of compounds with two exceptions Valsartan and Sulfamethoxazole in one type of water.