Direct Determination of Nimesulide in Natural Waters and Wastewater by Cathodic Stripping Voltammetry

Pharmaceuticals are included in a group of compounds considered as contaminants of emerging concern (CECs) in environmental matrices. The quantification of CECs is typically accomplished using chromatographic methods that require several sample pretreatment steps. The current study proposes a voltammetric method to quantify directly nimesulide (NIM) in aqueous samples. The voltammetric parameters were optimized and chosen based on the profile of the voltammograms and peak current intensity. The adequacy of the analytical method was evaluated using validation criteria, such as accuracy, selectivity, linearity, detection, and quantification limits. Linearity was assessed by a standard addition curve at a concentration range of 0.5-130 µg L^-1 of NIM. The limit of quantification was 0.50 µg L^-1, with 60 s of preconcentration time. Accuracy was expressed as recovery percentages of NIM and ranged from 111.4 to 119.8%. The voltammetric method herein proposed has several advantages over others already used to determine NIM, such as fewer sample pretreatment steps, faster, and cheaper analyses. NIM was detected in wastewater samples at concentration levels ranging from 101.7 to 385.0 µg L^-1. This result is the first evidence about NIM occurrences in environmental matrices in the area surrounding the Itaipu Lake reservoir in Brazil.