Electromembrane extraction (EME) is a liquid phase microextraction technique based on the voltage-assisted migration of the target analytes between two aqueous solutions (the sample and the acceptor phase) separated by a polymeric membrane where an organic solvent is immobilized in the form of a supported liquid membrane (SLM). The technique, which has been the subject of several posts in this blog, allows the rapid extraction of ionic species. The present post highlights a recent article, published in Journal of Pharmaceutical and Biomedical Analysis, where polyacrylamide gels are proposed as a membrane in EME.
Although polypropylene membranes are usually selected as a physical barrier between the two aqueous phases involved in EME, several research groups have proposed alternatives to this classical approach. In 2017, Tabani et al. proposed agarose gel as a greener alternative. Although good results were obtained, the large pore sizes of these gels (up to 300 nm) induce high electric currents which are associated with some disadvantages like bubbles generation or electroosmotic flow (the water migration produce a dilution of the analytes in the acceptor phase). The same group has recently proposed polyacrylamide gels for the same purpose. These gels present a more homogeneous pore size distribution, that can be tuned playing with the synthesis conditions, and smaller pore sizes (in the range of 20-140 nm).
The gel is synthesized in Eppendorf tubes which are finally cut (see Figure 1) leaving the gel in the open end and creating a small chamber for the location of the acceptor solution. The cut tube is immersed in the sample, and two electrodes are introduced in the donor and the acceptor phase for EME. The extraction has been studied for three basic drugs (pseudoephedrine, lidocaine, and propranolol) with good results.
|Figure 1. Extraction device. For extraction it is immersed into the sample and the two electrodes are connected|
The authors state that this EME approach involves three aqueous phases (donor, acceptor and that immobilized in the gel) and it does not require any organic solvent.
You can read the complete article where you can find all the specific information to synthesize the gel and the optimization of the extraction. The extraction in combination with LC-UV allows the determination of the target compounds in complex samples like wastewater and breast milk.
(1) Application of polyacrylamide gel as a new membrane in electromembrane extraction for the quantification of basic drugs in breast milk and wastewater samples. Link to the article