Electroextraction

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For the electrodeposition of metals, see Electrowinning also called electroextraction, is the electrodeposition of metals from their ores that have been put in solution via a process commonly referred to as leaching.

See Patented via Nth Cycle for metal electro-extraction process.[1]

Electroextraction (EE) is a sample enrichment technique that focuses charged analytes from a large volume of one phase into a small volume of aqueous phase through the application of an electric current.[2] The technique was originally developed as a separation technique for chemical engineering, but has since been coupled to capillary electrophoresis and liquid chromatography–mass spectrometry as a means of improving limits of detection, analysis time, and selectivity.[2][3][4] The use of EE-CE has made capillary electrophoresis more applicable to use in the pharmaceutical industry.

Nomenclature

The term electroextraction is used to describe multiple processes. In this article, electroextraction describes the extraction of charged particles through a liquid phase barrier. The term can be used to describe

bioproducts from a cell membrane using an electric field.[5]

Use in Chemical Engineering

Johann Stichlmair developed electroextraction at the

anions and cations. A two-phase system brings anions into one phase and cations into the other. A three phase system extracts anions and cations into the two outer phases while leaving uncharged particles in the middle phase.[6] Convective mixing is restricted to each phase and does not travel between phases. A diagram is given in figure 1. Organic phases that are used typically have small amounts of water added in order to be conductive. Other possible phases include mixtures of water and highly polymerized substances, or water with non-ionic surfactants.[3] Electroextraction has also influenced the development of similar electrophoretic separation techniques involving a membrane
between the two-phase systems.

Figure 1. A diagram of the electroextraction process. Particles cross the phase barrier while any convective mixing is constrained to each phase

Applications

Electroextraction has been successfully employed in the separation of

amino acids. This separation was done using an aqueous two-phase system of dextran-polyethylene glycol-water to stabilize the amino acids.[7] The velocity of a particle crossing the phase barrier is directly proportional to the strength of the applied electric field, so 100% separation is achieved with a strong enough field.[8]

Use in Analytical Chemistry

A diagram of an electroextraction apparatus is shown in figure 2. The apparatus consists of a vial with a conical bottom, a grounded platinum electrode, a capillary to inject the aqueous solution, and an adjustable gold anode with a circular bottom that contacts the entire organic phase.

Figure 2. A diagram of an electroextraction apparatus

EE is also often performed in a capillary electrophoresis capillary. This is referred to as capillary electroextraction, or cEE. In this set up, shown in figure 3, a capillary containing aqueous phase is placed in a vial of organic phase and surrounded by a hallow cathode. The outlet of the capillary is then grounded.[9]

Figure 3. A diagram of a capillary electroextraction apparatus

When EE is coupled to isotachophoresis coupled to capillary electrophoresis, limits of detection decrease to the nanomolar range and isotachophoresis takes only a few minutes to complete. Similar limits of detections are obtained when EE is coupled to liquid chromatography-mass spectrometry.[2] Similar limits of detections are obtained when EE is coupled to liquid chromatography-mass spectrometry.[4]

Applications

EE is ideal for

metabolites in urine for the purpose of studying metabolic processes.[12] In addition, EE-ITP-CE has been used in the determination of the drugs clenbuterol, salbutamol, terbutaline, and fenoterol.[13]

References

  1. ^ Nth Cycle, Nth Cycle. "Electrochemical metal deposition system and method". Google Patent.
  2. ^ a b c d van der Vlis; Mazereeuw; Tjaden; Irth; van der Greef. J. Chromatogr.. A 1994, 687, 333-341.
  3. ^ a b Stichlmair; Schmidt; Proplesch. Chem. Eng. Sci. 1992, 47, 3015-3022.
  4. ^ a b Lindenburg; Tempels; Tjaden; van der Greef; Hankemeier. J. Chromatogra., A 2012, 1249, 17-24
  5. ^ Electroextraction. http://www.electroextraction.org/ Archived 2013-03-26 at the Wayback Machine.
  6. ^ Kuban; Slampova; Bocek. Electrophoresis 2010, 31, 768-785.
  7. ^ Zhai, S.L.; Luo, G.S.; Liu, J.G. Chem. Eng. J. 2001, 83, 55-59.
  8. ^ Luo, G. S.; Yu, M. J.; Jiang, W. B.; Zhu, S. L.; Dai, Y. Y. Sep. Sci. Technol. 1999, 34, 781-791.
  9. ^ Lindenburg; Seitzinger; Tempels; Tjaden; van der Greef; Hankemeier. Electrophoresis 2010, 31, 3903-3912.
  10. ^ Stroink; Paarlberg; Waterval; Bult; Underberg. Electrophoresis, 2001, 22, 2374.
  11. ^ Palm; Marko-Varga. J. Pharm. Biomed. Anal. 2004, 35, 415.
  12. ^ Lindenburg; Tjaden; van der Greef; Hankemeier. Electrophoresis 2012, 33, 2987-2995.
  13. ^ Al-Majed; Analytical Profiles of Drug Substances and Excipients. 2001, 162, 429-441.
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