Comparative study of pesticide analysis in river water by gas chromatography/mass spectrometry screening and standard methods

• Compared the results of GC/MS screening and standard methods for pesticide analysis. • Both methods gave consistent pesticide identification results. • Screening method gave −48% to +45% error ranges compared to the standard method. • Quantitative errors in the screening method are controllable on prolonged application. • The GC/MS screening method can be utilized for water quality management. This study entailed a comparative analysis of the standard method (notification method) and the screening method based on gas chromatography/mass spectrometry (GC/MS) for detecting 168 pesticides. To clarify the qualitative and quantitative accuracy of the GC/MS screening method, the occurrence of pesticides in river water samples was determined using both methods. The lowest concentration in the calibration curves for 155 pesticides was 0.01 mg/L, corresponding to a limit of quantification (LOQ) of 0.01 μg/L in river water after accounting for the 1000-fold concentration factor from sample pretreatment. Except for two cases wherein the chromatogram showed interference peaks, both methods yielded consistent identification results. The quantitative values obtained by the screening method were 0.52–1.45 times (quantitative error ranging from −48% to +45%) those obtained by the notification method. The quantitative error associated with the screening method decreased significantly with increasing quantitative values. Calibration curves for each pesticide were prepared five times throughout the study period. Upon comparing with the initial calibration curve, the changes in these calibration curve slopes generally vary between −50% and +100% for each pesticide. Quantitative accuracy could be ensured by comprehensively maintaining the instrument conditions, even during prolonged use. This indicates that the quantitative errors of the screening method are controllable, although they are not equivalent to those of the notification method. Therefore, the GC/MS screening method can be effectively utilized for water quality management. To avoid underestimation of pesticide concentrations, the GC/MS screening method values may be multiplied by a safety factor of 2.