Development and Performance Evaluation of an Adapted QuEChERS-Gas Chromatography–Mass Spectrometry Method for the Analysis of Cocaine in Surface Water Samples

The consumption of illicit psychoactive substances, such as cocaine, poses significant public health and socioeconomic challenges due to its widespread use and impact on the central nervous system. This study aimed to develop and validate an analytical method for quantifying cocaine in surface water using an adapted QuEChERS extraction procedure and gas chromatography–mass spectrometry (GC-MS). The research included a bibliographic review of about 40 articles and laboratory analyses conducted at the Federal University of Northern Tocantins (UFNT). The results showed a matrix effect of −54.24%. This negative matrix effect impacted accuracy, as interference from other sample components can suppress the analyte signal, resulting in a smaller measured quantity. This indicates signal suppression, which can be corrected through matrix-matched calibration. Recovery values ranged from 61.3% to 107.7%, demonstrating satisfactory accuracy. The validated method proved suitable for monitoring cocaine in surface water and can serve as a biomarker for untreated sewage discharges.