Ultra‐High Performance Liquid Chromatography–Tandem Mass Spectrometry Method Development and Validation to Quantify Simultaneously Six Urinary DIALKYL Phosphate Metabolites of Organophosphorus Pesticides

The exposure to chemical pesticides is one of the world's concerns, especially in Vietnam, which is becoming a key player in global agriculture. The chronic long-term exposure to pesticides, especially organophosphorus groups poses increased health risks such as cancer and related diseases due to their hazardous metabolites. The characterization of urinary pesticides is essential to understand the pesticide exposure patterns. Therefore, this research aims to develop a liquid chromatography-tandem mass spectrometry procedure for the quantification of six dialkyl phosphate metabolites of organophosphorus pesticides based on simulated human urine containing dialkyl phosphates and urine samples of organophosphorus pesticides-exposed farmers in An Giang province of Vietnam. As a result, a highly sensitive procedure with a negative ion atmospheric pressure chemical ionization source, fosfomycin as internal standard and multireaction monitoring, was successfully validated in compliance with international guidelines for simultaneous quantitative determination of six dialkyl phosphates in human urine samples. Molecular and fragmented ions for quantification were consistent with the standard spectrum. The linear ranges of DMP, DEP, DMTP, DETP, DMDTP, and DEDTP were 5.29-1000.58, 5.10-1000.19, 5.10-1000.20, 5.06-1000.11, 5.06-1000.11, 5.30-1000.60, and 5.06-1000.12 ng/mL, respectively. The validation results showed that the selectivity, intraday and interday precision and accuracy, matrix effect, carry over, dilution, and stability of all the analytes were in the acceptable range. In total, 383 spot urine samples from people working with pesticides were satisfactorily analyzed by the proposed procedure. Over 80% of farmers were detected with at least one organophosphate metabolite, especially DEDTP with high concentrations, up to 5015.0 ng/mL, which alerts the high likelihood of pesticide exposure in the community of rural areas in Vietnam.