Abstract
Capillary gas chromatography (GC) with electron capture detection (ECD) and mass selective detection (MSD) was used for simultaneous determination of 2,4-dichlorophenoxyacetic acid (2,4-D), 3,6-dichloro-2-methoxybenzoic acid (dicamba), and (±)2-(4-chloro-2-methylphenoxy)propanoicacid (mecoprop) extracted from soil leachates. The 2,2,2-trif luoroethanol (TFE) esters of the acid analytes were synthesized by using H2SO4 as the catalyst. Efficiency of derivatization and instrumental molecular response were compared for herbicides methylated with boron trifluoride-methanol (14%, w/v), H2S04-methanol (33%, v/v), and diazomethane. The molecular integrity of TFE-2,4-D, TFE-dicamba, and TFE-mecoprop in the mixture was confirmed by GC-MSD. The TFE-esterification efficiency was maximized by adjusting the volume of H2SO4, the reaction time, and the reaction temperature. Optimal efficiency for the herbicide mixture was obtained by adding 1 m└ H2SO4 and 1 m└ TFE to the dried extract and allowing the reaction to proceed at 22�C for 8 h or by adding 0.5 m└ H2SO4 and 1 m└ TFE at 60°C for 120 min. Maximum esterification efficiency required an increased temperature and a decreased reaction time. The sensitivity of GC-ECD was about 2-20 times greater in determining TFE esters than in determining methyl ester derivatives. The herbicides were extracted simultaneously from soil leachates previously spiked with the analytes and esterified to TFE derivatives. Herbicide recovery, peak resolution, and detector sensitivity were excellent without column cleanup procedures.
Simultaneous Determination of 2,4-D, Dicamba, and Mecoprop in Soil Leachates by Gas Chromatography with Electron Capture Detection
