The purpose of this work is to demonstrate the usefulness of capillary electrophoresis (CE) instrumentation for determining values of critical micelle concentration (cmc) of surfactants. The approach essentially consists of a CE version of the traditional method of measuring values of cmc by conductivity. Namely, the different conductivities of ionic surfactants in solution depending on their aggregation state, i.e., as monomers or micelles, and the effect on the electrical current as usually measured in a CE apparatus are employed to determine the cmc values. The cmc of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) is obtained in several media such as water, aqueous solutions containing salts, organosaline solutions, and aqueous solutions containing β-cyclodextrin. The cmc values for SDS and CTAB under these conditions are in good agreement with those reported in the literature. Advantages and drawbacks of this procedure as well as its implications in micellar electrokinetic chromatography are discussed. From our results, it is deduced that the present method can be used with high confidence to determine values of cmc in a fast and easy way.

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The kinetic analysis and the characterization of copolymer systems at high conversion based on the free radical polymerization of N-vinylpyrrolidone, VP, and 2-hydroxyethyl methacrylate, HEMA, is analyzed on the basis of the reactivity ratios of these monomers as obtained by the Tidwell and Mortimer nonlinear method. Characterization of copolymers prepared at different conversion degrees was carried out by using micellar electrokinetic chromatography, MEKC, as well as by size exclusion chromatography, SEC. The experimental results obtained demonstrate a noticeable change of the composition of copolymer chains with the conversion degree and a good agreement between the approximation of the Skeist's kinetic treatment and the experimental data. Both MEKC and SEC provide valuable complementary information with respect to the average composition of copolymer chains and their macromolecular size and size distribution. To our knowledge this is the first time that MEKC has been applied to the characterization of high molecular weight copolymer systems.

Alpha‐1‐acid glycoprotein (AGP) presents different forms, which may arise from differences in the amino acid sequence and/or in the glycosidic part of the protein. Changes in forms of AGP have been described in literature as a possible tumor marker. While most previous works have approached the study of glycopeptides and/or glycans obtained after fragmentation of the protein, in this work, a CZE method is developed to separate up to eleven peaks of intact forms of AGP. A computer program developed in our laboratory is used to select the migration parameters that make possible an accurate assignment of AGP peaks. Electropherograms of AGP samples purified from sera of cancer patients and healthy donors are qualitatively and quantitatively compared. Percentages of correct assignment of AGP peaks close to 100% are achieved by using either the migration time of each peak relative to that of the EOF marker or the effective electrophoretic mobility of the peaks. The computer program permits to select, among different hypotheses for peak allotment, that one providing the highest accuracy of assignment. In this way, some peaks with different charge‐to‐mass ratio and a different distribution of area percentage of AGP forms are observed when comparing samples from sick and healthy individuals. Thus, a method that permits to compare AGP forms existing in sera of individuals with different pathophysiological situations has been developed. A potential for using AGP forms analyzed by CZE as a disease marker and for using this technique for screening purposes is envisaged.

Differences in alpha-1-acid glycoprotein (AGP) peptidic and glycan moieties originate several isoforms, whose modifications have been related to different pathophysiological situations. Differences in the isoforms of AGP existing in serum of individuals suffering from different diseases compared to healthy ones could be potentially used as biomarkers. CZE has been proven to be a useful technique for the analysis of glycoprotein isoforms. However, direct CZE analysis of AGP isoforms in serum samples needs efficient purification methods that allow the protein analysis. In this work two new and fast methods to purify AGP from human serum are evaluated in regard to their effect on the determination of isoforms of the intact glycoprotein by CZE-UV and by a developed CZE-ESI-TOF-MS method. Both preparation methods, which differ in the pre-treatment of the sample prior to an anti-AGP immunochromatographic step are shown to be adequate to analyze isoforms of intact AGP. Comparison of both purification methods by CZE-UV and CZE-ESI-TOF-MS indicates that serum AGP purified without acidic precipitation as pre-treatment is more adequate due to AGP higher yield, which leads to better CZE-Mass spectra. Both CZE methods show no indication that acidic precipitation influences the glycosylation (including sialylation) of AGP.

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