Validation of a multi-residue method and estimation of measurement uncertainty of pesticides in drinking water using gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry.

A rapid and efficient sample extraction using solid-phase extraction coupled with gas- and liquid-chromatography-mass spectrometry was studied for the analyses of 124 different types and chemical groups pesticides from drinking water. The extraction was performed using a Bond Elut Florisil cartridge. The GC analysis was divided into two (analysis 1 and 2), while a single method was used for LC analysis. A full validation of the method was performed. Linearity (1-250 ng/L range), intra-day precision (2.31-19.54% RSD) and inter-day precision (4.35-27.15% RSD), matrix effects (low matrix effects were observed for most compounds ≤20%) and limits of quantification (3.19 and 146.24 ng/L) were calculated. The recovery rates were between 55.54 and 121.21% (with RSD mean of 11.34% for all of the compounds). The method was suitable for 95.2% of the compounds. The information obtained from the full method validation has been used to estimate the expanded uncertainty and the uncertainty contributions of the different individual steps of the method for the determination of pesticides at trace levels in water. Expanded relative uncertainties ranged from 10% to 49%.