Capillary electrophoresis automation

Automated methods frequently exhibit remarkable performance not only in terms of sample throughput and cost, but in relation to the quality of results, especially in relation to repeatability and reproducibility. Several systems are currently available that enable simple automation of manual gestures these include automatic titra-tors, pH-meters with a circulating cell, etc., and involve approaches that are not fundamentally different to the corresponding manual method. These techniques are not, however, described in this chapter, nor are gas and liquid chromatography and capillary electrophoresis, automated techniques, that may be present but are not routinely used in oenological laboratories. 

M. A. Ruggiero and F. M. Ean as, Approaching the ideal system for the complete automation in ti ace analysis by capillaiy electi ophoresis , in Proceedings of the 3rd Latin American Symposium on Capillary Electrophoresis, Buenos Aires, Argentine, November 30-December 2. p. 1 (1997). 

There are many proteins in the human body. A few hundreds of these compounds can be identified in urine. The qualitative determination of one or a series of proteins is performed by one of the electrophoresis techniques. Capillary electrophoresis can be automated and thus more quantified (Oda et al. 1997). Newer techniques also enable quantitative determination of proteins by gel electrophoresis (Wiedeman and Umbreit 1999). For quantitative determinations, the former method of decomposition into the constituent amino acids was followed by an automated spectropho-tometric measurement of the ninhydrin-amino add complex. Currently, a number of methods are available, induding spectrophotometry (Doumas and Peters 1997) and, most frequently, ELISAs. Small proteins can be detected by techniques such as electrophoresis, isoelectric focusing, and chromatography (Waller et al. 1989). These methods have the advantage of low detection limits. Sometimes, these methods have a lack of specifidty (cross-over reactions) and HPLC techniques are increasingly used to assess different proteins. The state-of-the-art of protein determination was mentioned by Walker (1996). 

High performance capillary electrophoresis was introduced originally as an analytical tool. Now that instruments are equipped with automated fraction collection, however, capillary electrophoresis can be used for micropreparative collection of individual peaks separated from a mixture. Using the fraction collection feature, nanomolar amounts of solute such as proteins, peptides, oligonucleotides can be collected in amounts sufficient for microsequencing. An intersample washing procedure and use of well-formed capillaries aid in the prevention of artifacts.44... 

Miniaturized columns have provided a decisive advantage in speed. Uracil, phenol, and benzyl alcohol were separated in 20 seconds by CEC in an 18 mm column with a propyl reversed phase.29 A19 cm electrophoretic channel was etched into a glass wafer, filled with a y-cyclodextrin buffer, and used to resolve chiral amino acids from a meteorite in 4 minutes.30 A 6 cm channel equipped with a syringe pump to automate sample derivatization was used to separate amino acids modified with fluorescein isothiocyanate.31 Nanovials have been used to perform tryptic digests on the 15 nL scale for subsequent separation on capillary Electrophoresis.32 A microcolumn has also been used to generate fractions representing time-points of digestion from a 40 pL sample.33 A disposable nanoelectrospray emitter has been... 

Michels, D.A., Hu, S., Schoenherr, R.M., Eggertson, M.J., Dovichi, NJ. (2002). Fully automated two-dimensional capillary electrophoresis for high sensitivity protein analysis. Mol. Cell. Proteomics 1, 69-74. 

Riu et al. [542] has reported the determination of linear ethyl benzane-sulfates in coastal waters using automated solid-phase extraction followed by capillary electrophoresis with ultraviolet detection, and confirmed by capillary electrophoresis-mass spectrometry. The detection limits were 1 pg/1 when 250 ml of coastal water was preconcentrated. 

Figure 9.1 Schematic representation of a basic capillary electrophoresis system. The main components include a capillary (commonly contained within a housing that allows for temperature control), a power supply, and a detector. Automation is achieved through the use of computer-controlled setting of solutions and samples, displacement forces (to replace capillary contents and for hydrodynamic injection), and automatic data collection. (Courtesy of Agilent Technologies.)...

Complementary to IC, the capillary electrophoresis (CE) technique is useful for both anions and cations. The method is significantly faster than IC for screening and is relatively easy to automate which is advantageous when large numbers of samples require analysis. Although CE is currendy similar in terms of sensitivity to IC it is a relatively new technique and significant improvements in both selectivity and sensitivity continue to be made [26]. 

The first work on pKa determination by zone electrophoresis using paper strips was described by Waldron-Edward in 1965 (15). Also, Kiso et al. in 1968 showed the relationship between pH, mobility, and p/C, using a hyperbolic tangent function (16). Unfortunately, these methods had not been widely accepted because of the manual operation and lower reproducibility of the paper electrophoresis format. The automated capillary electrophoresis (CE) instrument allows rapid and accurate pKa determination. Beckers et al. showed that thermodynamic pATt, (pATf) and absolute ionic mobility values of several monovalent weak acids were determined accurately using effective mobility and activity at two pH points (17). Cai et al. reported pKa values of two monovalent weak bases and p-aminobenzoic acid (18). Cleveland et al. established the thermodynamic pKa determination method using nonlinear regression analysis for monovalent compounds (19). We derived the general equation and applied it to multivalent compounds (20). Until then, there were many reports on pKa determination by CE for cephalosporins (21), sulfonated azo-dyes (22), ropinirole and its impurities (23), cyto-kinins (24), and so on. 

JA Cleveland, MH Benko, SJ Gluck, YM Walbroehl. Automated pKa determination at low solute concentrations by capillary electrophoresis. J. Chromatogr. A 652 301-308 (1993). 

Development of batch process in 1987, coupled with fluorescent dideoxy-terminator labeling on target DNA, has allowed determination of fluorescence-tagged DNA sequences, separated on high-resolution slab-gels and more recently separated by capillary electrophoresis. Both separation methods are capable of sequencing up to 700 bases for each reaction. The automated DNA sequencer can simultaneously process up to 100 samples at a time within 3 hours and generate data for 100 unique DNA sequences with about 600-700 bases each. 

This area of analytical chemistry includes a great number of instruments that range from colour comparators and other visual comparison devices to automated spectrophotometers that can carry out multicomponent analysis. Liquid chromatography and capillary electrophoresis have accelerated the development of improved UV/Visible detectors, which are at the origin of the current mode of acquiring chromatograms, accompanied by the possibility of identification and quantification of compounds. 

Capillary electrophoresis is a new technique that combines the high resolving power of electrophoresis with the speed, versatility, and automation of... 

Capillary Electrophoresis. This technique, which appeared in the late 1980s. makes possible rapid and automated analysis of small volumes of complex mixtures with excellent resolution and sensitivity. The procedure is well described by M.J. Gordon el al. (see reference listed). 

Capillary electrophoresis is a commercially available technique, and has been integrated with most automated lab equipment such as autosamplers. 

Alternatives to two-dimensional electrophoresis are currently under development in these approaches, liquid chromatography or capillary electrophoresis is used for easier automation and capability of high-throughput application. 

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