Analysis methods capillary electrophoresis

Several variants of separation methods based on dialysis, ultrafiltration, and size exclusion chromatography have been developed that work under equilibrium conditions. Size exclusion chromatography especially has become the method of choice for binding measurements. The Hummel-Dreyer method, the vacancy peak method, and frontal analysis are variants that also apply to capillary electrophoresis. In comparison to chromatographic methods, capillary electrophoresis is faster, needs only minimal amounts of substances, and contains no stationary phase that may absorb parts of the equilibrium mixture or must be pre-equilibrated. 

Knowledge of the pKa value is crucial for analyzing both lipophilicity and solubility of ionizable compounds, as discussed above. Ionization equilibria also affect several toxicokinetic parameters, such as intestinal absorption, membrane permeability, protein binding, and metabolic transformations. Therefore, much research has been invested in developing both experimental and computational tools for pKa determination. Experimentally, two high-throughput methods exist spectral gradient analysis and capillary electrophoresis. However, the most definitive methods are still... 

Novotny MV (1996) Glycoconjugate analysis by capillary electrophoresis. In Karger BL, Hancock WS (eds) Methods enzymol, vol 271. Academic Press, NY, p 319... 

More success was obtained using on-line solid phase extraction before offline analysis by capillary electrophoresis with matrix-assisted laser-desorption ionization (MALDI) MS [18]. Because microdialysis is a method used for analysis of small molecules and peptides, MALDI is not used frequently with microdia lysis sampling. Another disadvantage is that MALDI cannot be used on-line with the separation because it is a vacuum ionization technique. However, if the pep-tide is large enough (0 1000 Da) MALDI can be useful. For the analysis of peptides in dialysate an appropriate separation is important before mass spectrometric detection. In a comparison with direct sampling of dialysate in MALDI, capillary electrophoresis provides the high efficiency separations necessary to resolve all... 

Aside from conventional electrophoretic methods, capillary electrophoresis (CE) is considered as a novel electrophoretic technique for protein separation with advantages of being easy, rapid, automatic, using trace amount of test samples, and qualitative as well as quantitative within one analysis... 

We have developed the method for quantitative analysis of urinary albumin with CE. A capillary electrophoresis systems Nanophor 01 (Institute of Analytical Instmmentation, Russian Academy of Sciences, Saint-Petersburg) equipped with a UV-detector was used to determine analyte. Separation was achieved using 45 cmx30 p.m I.D. fused silica capillary column with UV-detection at 214 nm. 

A. W. Moore-Jr, J. P. Lamiann-Jr, A. V. Lemmo and J. W. Jorgenson, Two-dimensional liquid chromatography-capillary electrophoresis teclmiques for analysis of proteins and peptides . Methods Enzymol. 270 401-419 (1996). 

To allow all culture productiou to be coutrolled, a method for rapid analysis is required. Prior to development of an LC-MS method, the analysis was both complex and time-consuming, involving the purification of a relatively large amount of the antibody using affinity chromatography, enzymatic release, and subsequent derivatizafion of the oligosaccharides and their analysis by using capillary electrophoresis. 

At present, the most promising methods for synthetic colorant analysis seem to be those based on separation approaches such as HPLC and capillary electrophoresis (CE). CE is the method of choice for the determination of synthetic dyes in biological materials while HPLC is generally a more suitable method for the identification and determination of hydrophobic natural pigments, having a better sensitivity and efficiency than CE. 

Frazierm, R.A. et ah. Development of a capillary electrophoresis method for the simultaneous analysis of colours, preservatives and sweeteners in soft drinks, J. 

Frazier, R.A., Ames, J.M., and Nursten, H.E., Method Development Capillary Electrophoresis for Food Analysis, Royal Society of Chemistry, Cambridge, 2000. 

Frazier, R. A. (2001). Recent advances in capillary electrophoresis methods for food analysis. Electrophoresis 22,4197-4206. 

A variety of formats and options for different types of applications are possible in CE, such as micellar electrokinetic chromatography (MEKC), isotachophoresis (ITP), and capillary gel electrophoresis (CGE). The main applications for CE concern biochemical applications, but CE can also be useful in pesticide methods. The main problem with CE for residue analysis of small molecules has been the low sensitivity of detection in the narrow capillary used in the separation. With the development of extended detection pathlengths and special optics, absorbance detection can give reasonably low detection limits in clean samples. However, complex samples can be very difficult to analyze using capillary electrophoresis/ultraviolet detection (CE/UV). CE with laser-induced fluorescence detection can provide an extraordinarily low LOQ, but the analytes must be fluorescent with excitation peaks at common laser wavelengths for this approach to work. Derivatization of the analytes with appropriate fluorescent labels may be possible, as is done in biochemical applications, but pesticide analysis has not been such an important application to utilize such an approach. 

The spectrum of new analytical techniques includes superior separation techniques and sophisticated detection methods. Most of the novel instruments are hyphenated, where the separation and detection elements are combined, allowing efficient use of materials sometimes available only in minute quantities. The hyphenated techniques also significantly increase the information content of the analysis. Recent developments in separation sciences are directed towards micro-analytical techniques, including capillary gas chromatography, microbore high performance liquid chromatography, and capillary electrophoresis. 

In the previously described electrophoretic methods, the capillary was filled with electrolytes only. Another mode of operation in capillary electrophoresis involves filling the capillary with gel or viscous polymer solutions. If desired, a column can be packed with particles and equipped with a frit.68 This mode of analysis has been favorably used for the size determination of biologically important polymers, such as DNA, proteins, and polysaccharides. The most frequently used polymers in capillary gel electrophoresis are cross-linked or linear polyacrylamide,69 cellulose derivatives,70-75 agarose,76 78 and polyethylene glycols. 

High performance capillary electrophoresis in its current form is a new technique. Its feasibility has been proven by the analysis and separation of small ions, drugs, chiral molecules, polymers, and biopolymers.93 We are learning more every day about the small tricks of the trade of the technique, and the efficiency and reproducibility of the methods are improving. 

A number of developments have increased the importance of capillary electrophoretic methods relative to pumped column methods in analysis. Interactions of analytes with the capillary wall are better understood, inspiring the development of means to minimize wall effects. Capillary electrophoresis (CE) has been standardized to the point of being useful as a routine technique. Incremental improvements in column coating techniques, buffer preparation, and injection techniques, combined with substantive advances in miniaturization and detection have potentiated rugged operation and high capacity massive parallelism in analysis. 

Li, J. Thibault, P. Martin, A. Richards, J. C. Wakarchuk, W. W. der Wilp, W. Development of an on-line preconcentration method for the analysis of pathogenic lipopolysaccharides using capillary electrophoresis-electrospray mass spectrometry—Application to small colony isolates. J. Chromatogr. A 1998, 817, 325-336. 

This book is organized into five sections (1) Theory, (2) Columns, Instrumentation, and Methods, (3) Life Science Applications, (4) Multidimensional Separations Using Capillary Electrophoresis, and (5) Industrial Applications. The first section covers theoretical topics including a theory overview chapter (Chapter 2), which deals with peak capacity, resolution, sampling, peak overlap, and other issues that have evolved the present level of understanding of multidimensional separation science. Two issues, however, are presented in more detail, and these are the effects of correlation on peak capacity (Chapter 3) and the use of sophisticated Fourier analysis methods for component estimation (Chapter 4). Chapter 11 also discusses a new approach to evaluating correlation and peak capacity. 

Jia, L., Liu, B., Terabe, S., Nishioka, T. (2004). Two-dimensional separation method for analysis of bacillus subtilis metabolites via hyphenation of micro-liquid chromatography and capillary electrophoresis. Anal. Chem. 76, 1419-1428. 

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