Low-voltage electromembrane extraction combined with cyclodextrin modified capillary electrophoresis for the determination of phenoxy acid herbicides in environmental samples

Abstract

In the present work, low-voltage electromembrane extraction (EME) combined with cyclodextrin (CD) modified capillary electrophoresis (CE) was applied for preconcentration and determination of some environmentally important pollutants, such as 2,4-dichlorophenoxyacetic acid (2,4-D), 4-(2,4-dichlorophenoxy) butanoic acid (2,4-DB), and 3,6-dichloro-2-methoxybenzoic acid (dicamba) in environmental samples. During the extraction, phenoxy acid herbicides migrated from a 4 mL aqueous sample solution through a thin layer of 1-octanol impregnated in the pores of a hollow fiber, into a 20 μL basic aqueous acceptor solution present in the lumen of the fiber. A Box–Behnken design (BBD) and response surface methodology (RSM) were used for optimization of different parameters related to extraction efficiency. The optimized extraction conditions were: 1-octanol as the supported liquid-membrane (SLM), 7 V potential difference, 24 min extraction time, donor phase pH 9.0 and acceptor phase pH 13.0. The method was reproducible so that intra and inter day RSD% were less than 4.8% by five replicate measurements for 70 ng mL⁻¹ of each herbicide. The developed method provided linearity with correlation coefficient values higher than 0.997 over a concentration range of 30–500 ng mL⁻¹ for 2,4-D and 2,4-DB, and 40–500 ng mL⁻¹ for dicamba. The limits of quantitation and detection for herbicides were obtained in the range of 30–40 and 10–15 ng mL⁻¹, respectively. Finally, the method was successfully applied for the extraction and determination of phenoxy acid herbicides from river water samples.