Nonaqueous CE

The mixing of solvents in various ratios tinned out to be a powerful optimization tool in nonaqueous CE, since a favorable ratio of mixture dielectric constant to its viscosity enhances separation efficiency and analysis speed. 

Besides its application as a separation technique, nonaqueous CE has also been used as a powerful method to measure fundamental physicochemical parameters in organic solvents and, thus, to contribute to a broader understanding of solvation phenomena, protolysis, and electochemistry in nonaqueous media. 

Dansyl-amino acids P Double reciprocal 60 nonaqueous CE (A-methylformamide), 17-correction... 

The most widely used separation medium in CE is water, that is, an aqueous medium. If an organic solvent has been used instead, the term nonaqueous CE (NACE) is used in order to make the difference. Nonaqueous solvents were first applied to conventional electrophoresis in the early 1950s [12,13]. The first NACE experiments were carried out in 1984 by Walbroehl and Jorgenson [14] and since then they have served as alternative media to the water environment in many electrophoretic applications [15-17]. 

If the samples are poorly soluble in aqueous media, then nonaqueous CE [5], capillary electrochromatography (CEC), or HPLC should be considered. 

Isoquinoline alkaloids Central European Corydalis species Nonaqueous CE-ESI-MS 46... 

Chcrkaoui and Veuthey have used nonaqueous CE for the simultaneous separation of nine nonsteroidal anti-inflammatory drugs. Separation was achieved using methanol/acetonitrile (40/60 v/v) with 20 mM ammonium acetate. Perhaps more important, the elution order of the individual components was shown to change with both solvent and electrolyte composition, indicating that selectivity can be manipulated. 

The range of analytes accessible to SP(M)E/CE is wide. Drugs, pollutants (and very hydrophobic ones like polyaromatic hydrocarbon, PAHs), proteins/peptides have all been determined using the methods described herein. There does not seem to be any sacrifice in separation modes, either. CE, capillary isoelectric focusing, MEKC, nonaqueous CE can all function with some form of SP(M)E. Methods of detection are similarly broad, encompassing at least the three most common optical absorbance, laser-induced fluorescence, and MS. It is perhaps foolish to attempt to generalize, but it does seem that an improvement in concentration detection limits of about 100-fold can be realized through SPME in conjunction with CE. 

Most of the analysis for drugs by CE utilizes either CZE in free solutions or MEKC in the presence of micelles. The two methods are complementary to each other. Drugs that are not sufficiently water soluble can be analyzed by nonaqueous CE (NACE). The separation in this method occurs in organic solvents in place of aqueous buffers. NACE offers several advantages for the analysis of such drugs, e.g., better solubility, different selectivity, and the ability to use higher voltages. 

Okada, T., Nonaqueous CE separation of polyethers and evaluation of weak complex formation, 7. Chromatogr. 4, 1995,695, 309-317. 

Heinig, K., C. Vogt, G. Werner, Anionic surfactants using aqueous and nonaqueous CE, 7. Capillary Electrophor., 1996,3, 261—270. 

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