Optimization of derivatization procedure and gas chromatography-mass spectrometry method for determination of bensulfuron-methyl herbicide residues in water.

A simple and efficient technique based on liquid phase extraction with CH2Cl2 solvent followed by derivatization with (C2H5)2O·BF3 solution and confirmation analysis with GC-MS analytical method was developed for detecting the bensulfuron-methyl (BSM) residues in water. Box-Behnken response surface methodology was employed for optimization of the derivatization efficiency. According to the optimization model, the derivatization time of 45min, derivatization temperature at 55°C and 0.2mL (C2H5)2O·BF3 solvent were selected as the optimal derivatization condition for obtaining the maximum desirability of response. Method validation was performed at 6 working standard levels (0.05, 0.1, 0.2, 0.5, 1.0, 5.0μg/mL) and the linearity of the calibration curve was linear well over the 6 fortification levels with the squared correlation coefficient of determination r(2)=0.998 and the LOD was found to be 0.1μg/L for BSM herbicide. The mean value of BSM was detected from 0.0414 to 4.7542μg/mL at levels from 0.05 to 5μg/mL with the recoveries remained at the acceptable level (42.8-95.0%) with the RSD values from 3.5% to 6.2%, which is more accptable and desirable than the results obtained by LC methods. Moreover, the method allowed the determination of BSM residue in real paddy field water samples at concentrations between 0.0902 and 3.4605μg/L. Average recovery rates of the BSM spiked at levels 0.1, 0.2, 0.5, 1.0μg/mL into thirty water samples ranged from 74.1% and 94.1% with the relative standard derivation (RSD) values from 1.9% to 6.7%.