In this study, accurate analytical method of the minimal detectable concentration was studied to determine of 2,4-dichlorophenoxyacetic acid(2,4-D) and 2,4,5-trichlorophenoxyacetic acid(2,4,5-T) in environmental samples using gas chromatography-tandem mass spectrometry(GC-MS/MS). for this purpose, the simultaneous analysis method of 2,4-D and 2,4,5-T with the most efficient derivatization was selected for comparison between SIM mode and SRM mode.
Methoxylation, ethoxylation, propoxylation of alkoxylation and trifluoroethoxylation and TMS, TBDMS of silyation were compared with the reaction temperature and time. we compared SIM mode with SRM mode to establish optimum reaction conditions for derivatization using GC-MS/MS. As a result, trifluoroethoxylation was chosen as analytical method using SRM mode that 2,4-D and 2,4,5-T are analyzed at the same time, both have an excellent sensitivity and high reproducibility and the lower instrument detection limit(IDL) in order to detect trace amounts. Calibration curve of optimised analysis method for validity certification using isotope dilution-GC-MS/MS was linear (R2=0.999) over the concentration range 0.5 ~ 50 ng/L. The accuracy results of 2,4-D and 2,4,5-T ranged from -4.52 % to -1.19 % and the precision results of 2,4-D and 2,4,5-T ranged 3.49 % to 6.07 %.
After 208 samples from national 40 water tretment plants were analysed by established derivatization, screening carried out in SIM mode and determination was performed in SRM mode. 2,4-D was detected in total 3 samples when the selected ion monitering(SIM) mode was used. Under Selected reaction monitoring(SRM) mode, the compound was not detected from one sample confirmed by detection in SIM mode but its detection could be checked at 6 samples confirmed by no detection in SIM mode. These results show that gas Chromatography-Tandem Mass Spectrometry can reduce quantitative errors caused by matrix effects due to mechanical advantage of the instrument operating in multi mode ionization.