Abstract:Abstract：A gas chromatography-tandem mass spectrometry （GC-MS/MS） was established for the determination of dichloracetic acid and trichloroacetic acid residues in drinking water.The differences in the derivatization reaction of dichloracetic acid and trichloroacetic acid by sulfuric acid-methanol solution and trimethylsilyl diazomethane（TMS-CHN2）hexane solution were compared.Sulfuric acid-methanol solution and TMS-CHN2hexane solution were used as the derivatization reagents for dichloracetic acid and trichloroacetic acid are reported in this paper.Samples of drinking water were extracted with methyl tert-butyl ether and then derived by sulfuric acid-methanol solution and TMS-CHN2hexane solution.A cleanup step using Florisil SPE cartridge was applied，and then quantified by external standard method in multiple reactions monitoring mode（MRM）.Under the optimized conditions，the target concentrations and peak areas were linearly correlated in the range of 0.005 mg/L-0.200 mg/L，and the correlation coefficients are greater than 0.99.Recovery studies were carried out on spiked matrices （three different water samples）with dichloracetic acid and trichloroacetic acid at spiking levels of 0.02，0.04，0.1 mg/L.The mean recoveries were 86.1%-96.5%，with relative standard deviations less than 5.2%.The response for the derivatives of dichloracetic acid and trichloroacetic acid by the TMS-CHN2hexane solution in water was 1.69，1.71 times of dichloracetic acid and trichloroacetic acid by the sulfuric acid-methanol solution.The method of TMS-CHN2hexane solution derivation was adopted，which greatly reduces the detection time，improves the detection efficiency，reduces the detection cost，and is conducive to the daily detection of a large number of water samples.