Optimization capillary electrophoresis

McClean, S., O Kane, E. J., and Smyth, W. E (2000). The identification and determination of selected 1,4-benzodiazepines by an optimized capillary electrophoresis-electrospray mass spectro-metric method. Electrophoresis 21, 1381 — 1389. 

Enantioresolution in capillary electrophoresis (CE) is typically achieved with the help of chiral additives dissolved in the background electrolyte. A number of low as well as high molecular weight compounds such as proteins, antibiotics, crown ethers, and cyclodextrins have already been tested and optimized. Since the mechanism of retention and resolution remains ambiguous, the selection of an additive best suited for the specific separation relies on the one-at-a-time testing of each individual compound, a tedious process at best. Obviously, the use of a mixed library of chiral additives combined with an efficient deconvolution strategy has the potential to accelerate this selection. 

Jandik, P. and Jones, W. R., Optimization of detection sensitivity in the capillary electrophoresis of inorganic anion, /. Chromatogr., 546, 431, 1991. 

Capillary zone electrophoresis coupled with fast cyclic voltammetric detection was developed by Zhou et al. [27] for the separation and determination of OTC, TC, and CTC antibiotics. All compounds were well separated by optimization of pH and complexation with a boric acid sodium tetraborate buffer. The detection limit using fast on-line cyclic voltammetric detection with Hg-film-microm electrode was 1.5 x 10-6 mol/L for OTC (signal to noise ratio > 2). A continuous flow manifold coupled on-line to a capillary electrophoresis system was developed by Nozal et al. [28] for determining the trace levels of OTC, TC, and DC in surface water samples. 

Valproic acid has been determined in human serum using capillary electrophoresis and indirect laser induced fluorescence detection [26], The extract is injected at 75 mbar for 0.05 min onto a capillary column (74.4 cm x 50 pm i.d., effective length 56.2 cm). The optimized buffer 2.5 mM borate/phosphate of pH 8.4 with 6 pL fluorescein to generate the background signal. Separation was carried out at 30 kV and indirect fluorescence detection was achieved at 488/529 nm. A linear calibration was found in the range 4.5 144 pg/mL (0 = 0.9947) and detection and quantitation limits were 0.9 and 3.0 pg/mL. Polonski et al. [27] described a capillary isotache-phoresis method for sodium valproate in blood. The sample was injected into a column of an EKI 02 instrument for separation. The instrument incorporated a conductimetric detector. The mobile phase was 0.01 M histidine containing 0.1% methylhydroxycellulose at pH 5.5. The detection limit was 2 pg/mL. 

Optimization and applications of CL detection in flow injection and liquid chromatographic analysis and the relatively new use of CL in capillary electrophoresis are extensively described. Particular interest is attached to the universally applied peroxyoxalate CL reactions, as well as to the applications of new acridan esters in immunoassay. Obviously, the related applications of BL and CL imaging techniques in analytical chemistry, and the increasing importance of these techniques in DNA analysis—including the recent strategies in the development of CL sensors—are also presented. 

Analytical methods are ripe for attack using Al methods. Capillary electrophoresis is a routine separation technique, but like other separation techniques, its effectiveness is correlated strongly with experimental conditions. Hence it is important to optimize experimental conditions to achieve the maximum degree of separation. Zhang and co-workers41 studied the separation of mixtures in reserpine tablets, in which vitamin B1 and dibazolum may be incompletely separated, as may promethazine hydrochloride and chloroquine... 

Fused silica capillaries are almost universally used in capillary electrophoresis. The inner diameter of fused silica capillaries varies from 20 to 200 pm, and the outer diameter varies from 150 to 360 pm. Selection of the capillary inner diameter is a compromise between resolution, sensitivity, and capacity. Best resolution is achieved by reducing the capillary diameter to maximize heat dissipation. Best sensitivity and sample load capacity are achieved with large internal diameters. A capillary internal diameter of 50 pm is optimal for most applications, but diameters of 75 to 100 pm may be needed for high sensitivity or for micropreparative applications. However, capillary diameters above 75 pm exhibit poor heat dissipation and may require use of low-conductivity buffers and low field strengths to avoid excessive Joule heating. 

Jimidar, M.I., Vennekens, T., Van Ael, W., Redlich, D., De Smef M. Optimization and validation of an enantioselective method for a chiral drug with eight stereo-isomers in capillary electrophoresis. Electrophoresis 2004, 25, 2876-2884. 

The origins, principles, methods, and modes of capillary electrophoresis (CE) are discussed. Massive application of electrophoresis methods started after Tiselius s moving boundary method that was optimized by the use of paper or a gel as a semiconducting medium. The applications of paper and gel electrophoresis were situated mostly in the biochemical environment for the analysis of proteins, amino... 

Jimidar, M., Van Ael, W, and De Smet, M. (2004). Optimization of enantiomeric separations in capillary electrophoresis based on a screening approach. /. Capillary Electrophor. Microchip Technol. 9(1 and 2), 13-21. 

This chapter discusses general considerations for improving capillary electrophoresis (CE) method performance from a robustness angle. Several method parameters are discussed and examples are offered of how CE procedures are handled to obtain optimal performance. The purpose of this chapter is to raise the awareness and help the development of more robust and sensitive methods. 

Salas-Solano, O., Tomlinson, B., Du, S. B., Parker, M., Strahan, A., and Ma, S. (2006). Optimization and validation of a quantitative capillary electrophoresis sodium dodecyl sulfate method for quality control and stability monitoring of monoclonal antibodies. Anal. Chem. 78(18), 6583-6594. 

Persson Stubberud, K., and Astrom, O. (1998). Separation of ibuprofen, codeine phosphate, their degradation products and impurities by capillary electrophoresis I. Method development and optimization with fractional factorial design. ]. Chromatogr. A 798, 307—314. 

Pranfois, C., Morin, P., and Dreux, M. (1995). Separation of transition metal cations by capillary electrophoresis, optimization of complexing agent concentrations (lactic acid and 18-crown-6).. Chromatogr. A 717, 393—408. 

Samskog, J., Wetterhall, M., Jacobsson, S., and Markides, K. (2000). Optimization of capillary-electrophoresis conditions for coupling to a mass-spectrometer via a sheathless interface. ]. Mass Spectrom. 35, 919—924. 

Lazar, I. M., Lee, E. D., Rockwood, A. L., and Lee, M. L. (1998). General considerations for optimizing a capillary electrophoresis-electrospray ionization time-of-flight mass-spectrometry system./. Chromatogr. A 829, 279 — 288. 

SG Penn, ET Bergstrom, DM Goodall, JS Loran. Capillary electrophoresis with chiral selectors. Optimization of separation and determination of thermodynamic parameters for binding of ticonazole enantiomers to cyclodextrins. Anal Chem 66 2866-2873, 1994. 

Capillary electrophoresis has been applied for the enantioselective determination of the binding constants of chiral drugs with cyclodextrins for basically the following two reasons (1) optimization of chiral selector concentration and (2) understanding the fine mechanisms of enantioseparations in CE. The first group of studies have been published mainly on the early stage of chiral CE development, whereas the second goal is followed in the most recent studies, mainly by Rizzi and Kremser (10,13) and Scriba et al. 

Finally, when RPC methods are used in preparative studies with peptides, the opportunity routinely exists for subsequent analysis of the recovered fractions by a variety of analytical methods including high-speed RP-HPLC, HP-IEX, HP-HILIC, or HP-IMAC, zonal or micellar electrokinetic high-performance capillary electrophoresis (HP-CZE and MECK-CZE), capillary electrochromatography (CEC), or capillary isotachophoresis. The combination of the RPC information, drawn from the In k versus i > plots, with the data derived from on-line spectroscopic detection thus readily provides a comprehensive opportunity to assess the purity of an isolated peptide, many of the physicochemical features of the interaction, as well as a means to optimize the resolution in the RPC separation. 

Determination of inorganic anions by capillary electrophoresis is critically compared with ion chromatographic determinations on the basis of recent literature in the field. After a very brief summary of the theoretical background, the selection and optimization of the running electrolyte system are discussed, especially in connection with modification of the electroosmotic flow. Preconcentration techniques are surveyed, as are the approaches to the sample introduction and analyte detection. The principal analytical parameters of the determinations are evaluated and illustrated on selected applications described in the literature. 1997 Elsevier Science B.V. 

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