Determination of three phenoxyacid herbicides in environmental water samples by the application of dispersive liquid-liquid microextraction coupled with micellar electrokinetic chromatography

摘要

An effcient method based on dispersive liquid-liquid microextraction coupled with micellar electrokinetic chromatography has been developed for determination of three phenoxyacid herbicides (PAs) of 2,4-dichlorophenoxybutyric acid (2,4-DB), dicamba and 2,4-dichlorophenoxyacetic acid (2,4-D), in environmental water samples. The types and volumes of extracting and dispersing solvents, ionic strength, extraction and centrifugation time and centrifugation speed were investigated. Successful separation of the three PAs was achieved within 7 min, by using the background electrolyte solution consisting of 10 mmol L~(-1) sodium tetraborate, 25 mmol L~(-1) sodium dodecyl sulfate and 15% (v/v) methanol, at pH 9.75. Excellent analytical performances were attained, such as good linear relationships (R ≥0.9993) between peak area and concentration for each PAs from 10-1000 ng mL~(-1) , limits of detection of 1.56-1.91 ng mL~(-1) , and intra-day precisions at two spiked levels in terms of migration time and peak area within the range of 0.22-0.42% and 3.88-6.39%, respectively. Enrichment factors of 2,4-DB, dicamba and 2,4-D were 180, 151 and 216, respectively. The method recoveries obtained at for tifed 20.0, 50.0 and 100.0 ng mL~(-1) for lake, river and reservoir water samples varied from 67.91 to 119.07% with the relative standard deviation of 1.47-6.89%.