Methodology for determining the residual content of active ingredients of agrochemicals in surface waters

Agricultural water bodies are multifunctional objects in the agricultural production cycle. Residual amounts of the active ingredients of pesticide agrochemicals can enter and contaminate a water body during some agro-technological tasks. The purpose of this study was to investigate the conditions for the extraction of residual amounts of xenobiotics from surface water containing suspended particles and to measure their content by chromatographic methods. To determine the optimal conditions for the extraction of target xenobiotics, the values of the lipophilicity parameters of their molecules were considered. The methodology for determining the content of lipophilic xenobiotics by chromatographic methods with mass-selective detection in surface water samples includes a step of separating suspended particles, the content of which in the samples under study was controlled by gravimetric analysis and varied within 135-1500 mg/m3. The target compounds were extracted using n-hexane and acetonitrile. The analytes in the acetonitrile concentrate were determined according to high-performance liquid and gas chromatography with mass-selective detectors (HPLC/MS/MS and GC/MS). The achieved limit of detection of xenobiotics was 0.02 µg/m3, the limit of quantification of xenobiotics was 0.10 µg/m3. To substantiate the possibility of applying the proposed methodology, the following indicators were investigated: linearity of analytical signals with the amount of analytes in the solution, correctness, convergence, and accuracy of measurement results. The linear concentration range of the method for the determination of xenobiotics of diverse groups is 0.10-1.00 µg/m3, characterised by a regression coefficient of the linear dependence of the measurement of individual compounds (R2) exceeding 0.99. The degree of analytes recovery (percentage of recovery r, %) was within 85-120%, which indicates the acceptability of the proposed xenobiotic extraction procedure. The error of the measurement results was calculated as the standard deviation (Sr, %), which did not exceed 6%. The findings of this study suggested that the developed methodology is suitable for monitoring the residual content of active ingredients of agrochemicals in surface waters and predicting the level of water pollution