Electromembrane Extraction Report

Electromembrane Extraction (EME)
Principle
Electromembrane extraction (EME) selectively extracts compounds of interest by employing electromigration across liquid membranes. In EME, the driving force of solutes is potential difference across the SLM. A platinum electrode is located in the donor sample solution, and the other platinum electrode is placed in the acceptor solution. Charged solutes that are desired to be extracted in the donor solution diffuse across the SLM toward the oppositely charged electrode in the acceptor solution. Upon completion of the extraction, the acceptor solution can be transferred to a vial to perform analysis by GC, HPLC, CE or any other analytical techniques. The setup used for EME is shown in figure 7. (5)

Source: Sihvonen M, Jarvenpaa E, Hietaniemi V, Huopalahti R. Advances in supercritical carbon dioxide technologies. Trends Food Sci Technol. 1999;10(6–7):217–22.

Application
The automated systems available are mainly dealed with environmental analysis. SFE is used to extract pharmaceuticals from liquid and solid samples. The other widely used industrial applications are tobacco extraction, extraction of fats and oils and making of spice extracts.(5)
SFE is mainly used for the extraction of bioactive compounds from a mixture for purification, quantification of active enantiomer, extraction from natural matrices, etc. SFE is effective in separating enantiomers. For example a simple resolution for the enantiomers of trans-1,2-cyclohexanediol by diastereomeric complex formation with tartaric acid and subsequent supercritical fluid extraction is developed.(7)

Solid-phase Extraction (SPE)
Principle
SPE is a selective extraction technique where the compounds of interest are partitioned between a sorbent phase and a sample liquid in a cartridge, where these compounds must have greater affinity for the sorbent phase than for the sample liquid. The choice of sorbents depends on the interaction of compounds of interest and the chosen sorbent through the functional groups of the compounds. Typically, sorbents used in SPE consists of 40μm diameter silica gel with approximately 60 Aº pore diameters. The steps in SPE is described in

Fiber SPME is a new sample preparation technique using a fused-silica fiber coated on the outside with an appropriate stationary phase. In-tube SPME is suitable for automation, and extraction, desorption and injection can be done continuously using a standard autosampler. Drawing and ejection of the sample solution, switching of the valves, control of peripheral equipment such as the HPLC and MSD, and analytical data processing are all computer controlled.(9)

Application
SPME is widely applied in pharmaceutical analysis. The types of compounds that can be analysed by SPME range from non-polar to semi-polar materials due to the different sorbent materials available. This extraction technique has become a standard technique, with fully automated systems available. The following outlined some of the applications of SPME that are widely employed. (9)
1. Analysis of amphetamines in urine using PDMS fiber.
2. Toxicological analysis of the local anesthetic lidocaine in biological fluids.
3. Analysis of benzodiazepines in plasma and urine using PDMS/DVB and CW/TPR