Simplified method for determination of polycarbamate fungicide in water samples by liquid chromatography with tandem mass spectrometry following derivatization with dimethyl sulfate

A simple and sensitive analytical method for the determination of polycarbamate in water samples was developed. In this method, polycarbamate was cleaved under alkaline conditions and derivatized with dimethyl sulfate to methyl dimethyldithiocarbamate (DMDC-methyl) and dimethyl ethylenebisdithiocarbamate (EBDC-dimethyl). After the solid-phase extraction of the resulting methyl derivatives, they were measured by liquid chromatography with tandem mass spectrometry (LC–MS/MS), based on reversed-phase separation and MS/MS detection with positive atmospheric pressure chemical ionization. The absolute recoveries (mean ± SD) all through the procedure from polycarbamate to DMDC-methyl and EBDC-dimethyl were 62.6 ± 4.3 and 73.5 ± 5.9%, respectively. The limits of detection and quantification of polycarbamate in the water samples were 0.061 and 0.20 μg/L in the form of DMDC-methyl, and 0.032 and 0.11 μg/L in the form of EBDC-dimethyl, respectively. The method was validated at levels of 0.25, 1.0, and 5.0 μg/L in the tap water and river water samples, and accuracy was achieved in the range of 94–109%. The proposed method can be applied to the determination of trace amounts of polycarbamate in environmental water samples.