Development of ionic liquid based electromembrane extraction and its application to the enrichment of acidic compounds in pig kidney tissues

Abstract

The ionic liquid-based electromembrane extraction (IL-EME) is presented for the determination of acidic compounds in complex biological samples for the first time. In this work, the IL was held in the hollow fiber pores serving as the supported liquid membrane (SLM). An aqueous acceptor solution was placed in the lumen of hollow fiber. The acidic analytes migrated in the electric field, and were eventually enriched in the acceptor phase. In this extraction mode, electrokinetic migration served as the primary driving force, which significantly increased the extraction efficiency, resulting in a considerable increase in the extraction rate. Four chlorophenoxy acid herbicides, namely, 2,4-dichlorophenoxy acetic acid, 2-(2,4-dichlorophenox)propionic acid, 4-chloromethylphenoxyacetic acid, and 2,4,5-trichlorophenoxyacetic acid were used as the model analytes to test the applicability of IL-EME for acidic compounds. And the pig kidney was chosen as the sample matrix. Prior to the microextraction, some pretreatments including homogenating, shaking together with NaOH and centrifugating were needed for the kidney tissues. Important parameters affecting the extraction efficiency, such as the type of SLM, voltage, sample solution and acceptor phase pH, extraction time, temperature, stirring rate and salt addition were also investigated and optimized. Under the optimized conditions, the extraction procedure was completed within 15 min with 78–90 folds enrichment factors and the spike recoveries were in the range of 87.5–97.8%. Moreover, high linearities over 10.0 μg L⁻¹ to 640 μg L⁻¹ were obtained. The correlation coefficients exceeded than 0.9900.