Capillary electrophoresis of carboxylated carbohydrates. I. Selective precolumn derivatization of gangliosides with UV absorbing and fluorescent tags

Reversed-phase capillary electrochromatography of pre-column derivatized mono- and oligosaccharides with three different ultraviolet absorbing tags

In this research report, an in house developed octadecyl monolithic (ODM) column has been exploited in the reversed-phase capillary electrochromatography (RP-CEC) of precolumn derivatized mono- and oligosaccharides with three different tagging agents, namely 1-naphthylamine (1-NA), 2-aminoanthracene (2-AA) and 3-amino-2,7-naphthalenedisulfonic acid (ANDSA). These three derivatizing agents, which differed in their charges, nonpolar characters and optical absorption properties, led to different RP-CEC elution patterns and UV detection signals. In fact, the limit of detection of the derivatized sugars were 50 µM for the ANDSA- and 1-NA-sugar derivatives and 35 µM for the 2-AA-sugar derivatives due to the presence of three fused aromatic rings in 2-AA versus 2 fused rings in the 1-NA and ANDSA tags. Furthermore, while the longer ANDSA-oligosaccharides eluted later than the shorter ones and the ANDSA-monosaccharides, 1-NA- and 2-AA-sugar derivatives necessitated the presence of borate ions at alkaline pH in the mobile phase to form in situ charged derivatives to facilitate their separation by RP-CEC, and the elution order was the reversal of that observed with the ANDSA-sugar derivatives; that is the mono- eluted later than the larger size oligosaccharides. In addition, plots of log t_R vs. number of glucose residues (n_Glc) for derivatized glucose and maltooligosaccharides yielded straight lines with slopes representing log η where η is the retention time modulus (i.e., ratio of retention time of two neighboring derivatives differing in one glucosyl residue). In the case of 1-NA and 2-AA derivatives, η was smaller than unity while it was greater than unity in the case of ANDSA-sugar derivatives because the elution occurred in the order of decreasing size of the homologous sugar derivatives in the former than in the later derivatives. The prepared ODM column was stable for more than a month of continuous use, a fact that allowed a good repeatability for intraday and interday analyzes.

Development and validation of capillary electrophoresis method for quantification of gangliosides in brain synaptosomes

Gangliosides are sialic acid containing glycosphingolipids of the plasma membrane with diverse biological functions. They are most abundant in neural tissues where their dysregulation has been suggested to be involved in various pathological conditions. Due to their importance, efficient analytical methods are needed to determine individual gangliosides in biological samples. Here we report a capillary electrophoresis method, optimized and validated for the simultaneous quantification of major neural gangliosides GM1, GD1a, GD1b, GT1b and GQ1b in their underivatized form. The most abundant extraneural monosialogangloside, GM3 can also be separated by this method. Micelles of the highly amphiphilic gangliosides were disrupted with cyclodextrins (CyDs) in the aqueous separation buffer. Among the tested CyDs, the best resolution was observed using 20 mM randomly methylated alpha-CyD in alkaline sodium borate buffer enabling the separation of all studied gangliosides. The method was applied for the quantification of gangliosides in rat cerebral and cerebellar synaptosomes.

6-Polyamino-substituted quinolines: synthesis and multiple metal (CuII, HgII and ZnII) monitoring in aqueous media

Chemoselective palladium-catalyzed arylation of polyamines with 6-bromoquinoline has been explored to prepare chelators for the detection of metal cations in aqueous media. The introduction of a single aromatic moiety into non-protected polyamine molecules was achieved using the commercially available Pd(dba)2/BINAP precatalyst to afford nitrogen chelators, in which the aromatic signalling unit is directly attached to the polyamine residue. Water-soluble receptors were then synthesized using N-alkylation of these polyamines by hydrophilic coordinating residues. By combining rich photophysical properties of the 6-aminoquinoline unit with a high coordination affinity of chelating polyamines and a hydrophilic character of carboxamido-substituted phosphonic acid diesters in a single molecular device, we synthesized chemosensor 5 for selective double-channel (UV-vis and fluorescence spectroscopies) detection of CuII ions in aqueous media at physiological levels. This receptor is suitable for the analysis of drinking water and fabrication of paper test strips for the naked-eye detection of CuII ions under UV-light. By increasing the number of donor sites we also obtained chemosensor 6 which is efficient for the detection of HgII ions. Moreover, chemosensor 6 is also suitable for multiple detection of metal ions because it chelates not only HgII but also CuII and ZnII ions displaying different responses of emission in the presence of these three cations.

A High-Throughput Mass-Spectrometry-Based Assay for Identifying the Biochemical Functions of Putative Glycosidases

The most commonly employed glycosidase assays rely on bulky ultraviolet or fluorescent tags at the anomeric position in potential carbohydrate substrates, thereby limiting the utility of these assays for broad substrate characterization. Here we report a qualitative mass spectrometry-based glycosidase assay amenable to high-throughput screening for the identification of the biochemical functions of putative glycosidases. The assay utilizes a library of methyl glycosides and is demonstrated on a high-throughput robotic liquid handling system for enzyme substrate screening. Identification of glycosidase biochemical function is achieved through the observation of an appropriate decrease in mass between a potential sugar substrate and its corresponding product by electrospray ionization mass spectrometry (ESI-MS). In addition to screening known glycosidases, the assay was demonstrated to characterize the biochemical function and enzyme substrate competency of the recombinantly expressed product of a putative glycosidase gene from the thermophilic bacterium Thermus thermophilus.

Preparation and electrophoretic separation of Bodipy-Fl-labeled glycosphingolipids

Several glycosphingolipids were labeled with the fluorphore Bodipy-Fl and analyzed using capillary electrophoresis with laser-induced fluorescence detection. GM1-, LacCer-, and Cer-Bodipy-Fl were prepared through acylation using the N-hydroxysuccinimide ester of Bodipy-Fl. Several other glycosphingolipids including GT1a-, GD1a-, GM2-, GM3-, GD3-, and GlcCer-Bodipy-Fl were enzymatically synthesized. Micellar electrokinetic capillary chromatography with a TRIS/CHES/SDS/α-cyclodextrin buffer produced better separation than an established borate/deoxycholate/methyl-β-cyclodextrin buffer. The nine Bodipy-Fl-labeled glycosphingolipid standards were separated in under 5 min, theoretical plate counts were between 640,000 and 740,000, and the limit of detection was approximately 3 pM or 240 ymol analyte injected onto the capillary.

Capillary electrophoresis of acidic oligosaccharides from human milk

Interest in defining the array of oligosaccharides of human milk has been increasing. Pathogens that bind glycans on their host mucosal surfaces may be inhibited by human milk oligosaccharides. It has been postulated that acidic oligosaccharides in human milk may inhibit binding by pathogens that bind acidic glycans in the gut, but testing this hypothesis requires their reliable quantification in milk. Sialyloligosaccharides of human milk have been quantified by HPLC and CE. A recent CE technique uses the MEKC mode with direct detection at 205 nm to resolve and quantify, in the native form, the 12 most dominant sialyloligosaccharides of human milk in a single 35-min run. The method gives a linear response from 39 to 2500 microg/mL with a coefficient of variation between 2 to 9% and accuracy from 93 to 109%. This was used to detect variation in expression of specific sialyloligosaccharides in milk. Individual sialyloligosaccharide concentrations in milk differ among individual donors and between less and more mature milk. Thus, CE can be used to measure variation in sialyloligosaccharide expression in milk, and thereby test the relationship of this variation-to-variation in risk of specific diseases in breastfed infants.

Positional isomers of sulfated oligosaccharides obtained from agarans and carrageenans: preparation and capillary electrophoresis separation

Partial reductive hydrolysis was used to produce oligosaccharide alditols from repetitive sulfated galactans obtained from four Rhodophyta species: kappa-carrageenan (from Kappaphycus alvarezii), theta-carrageenan (Gigartina skottsbergii-alkali-treated lambda-carrageenan), agarose 6-sulfate (Gracilaria domingensis), and pyruvylated agarose 2-sulfate (Acanthophora spicifera-alkali-treated pyruvylated agaran sulfate). Each hydrolyzate was submitted to anion-exchange and gel-filtration chromatography, and the isolated oligosaccharide alditols were identified by 1D and 2D NMR spectroscopy and by ESI mass spectrometry. The positional isomers of the sulfated oligosaccharide alditols were then completely resolved by capillary electrophoresis in a borate buffer. Attempts to correlate the availability of the hydroxyl groups for borate complexation with the relative migration of the oligosaccharides are presented.

Derivatization of carbohydrates for chromatographic, electrophoretic and mass spectrometric structure analysis

Carbohydrates, either alone or as constituents of glycoproteins, proteoglycans and glycolipids, are mediators of several cellular events and (patho)physiological processes. Progress in the "glycome" project is closely related to the analytical tools used to define carbohydrate structure and correlate structure with function. Chromatography, electrophoresis and mass spectrometry are the indispensable analytical tools of the on-going research. Carbohydrate derivatization is required for most of these analytical procedures. This review article gives an overview of derivatization methods of carbohydrates for their liquid chromatographic and electrophoretic separation, as well as the mass spectrometric characterization. Pre-column and on-capillary derivatization methods are presented with special emphasis on the derivatization of large carbohydrates.

Microchip capillary electrophoresis coupled to sinusoidal voltammetry for the detection of native carbohydrates

The development of a microchip electrophoresis system involving integrated frequency based electrochemical detection is described. The use of poly(dimethylsiloxane) (PDMS) as the channel substrate greatly simplifies the fabrication process while decreasing cost and time consumption. Characterization of this system is accomplished through the detection of native carbohydrates at planar copper electrodes. Various photolithographic techniques are explored in the optimization of electrode area. Separation efficiency of 1 x 10(5) theoretical plates per meter is demonstrated. Sinusoidal voltammetry utilizes information in the frequency domain to achieve sensitive detection through either of two approaches, maximization of signal or minimization of noise. Mass detection limits (S/N = 3) of less than 200 amol have been accomplished for glucose and sucrose. Sinusoidal voltammetry also facilitated the selective isolation of an analyte signal from a pair of chromatographically unresolved species through the use of phase discrimination.

Capillary electrophoresis for the analysis of glycosaminoglycans and glycosaminoglycan-derived oligosaccharides

Glycosaminoglycans are a family of polydisperse, highly sulfated complex mixtures of linear polysaccharides that are involved in many life processes. Defining the structure of glycosaminoglycans is an important factor in elucidating their structure-activity relationship. Capillary electrophoresis has emerged as a highly promising technique consuming an extremely small amount of sample and capable of rapid, high-resolution separation, characterization and quantitation of analytes. Numerous capillary electrophoresis methods for analysis of intact glycosaminoglycans and glycosaminoglycan-derived oligosaccharides have been developed. These methods allow for both qualitative and quantitative analysis with a high level of sensitivity. This review is concerned with separation methods of capillary electrophoresis, detection methods and applications to several aspects of research into glycosaminoglycans and glycosaminoglycan-derived oligosaccharides. The importance of capillary electrophoresis in biological and pharmaceutical samples in glycobiology and carbohydrate biochemistry and its possible applications in disease diagnosis and monitoring chemical synthesis are described.

Structure analysis of lipoglycans and lipoglycan-derived carbohydrates by capillary electrophoresis and mass spectrometry

Lipoglycans (lipopolysaccharides, lipoarabinomannans and glycolipids) are unique components of the cell membrane of all cells and the envelope of many bacteria. They play important roles in determining cell-environment interactions, which, however, are only partly understood due to incomplete description of their structural components, lipids and glycans. Capillary electrophoresis is an analytical technique of high separation efficiency and minimum sample requirements and has successfully been used for the analysis of several molecules of biological importance: proteins, nucleic acids and glycoconjugates. In the last years, a few applications of capillary electrophoresis to the analysis of lipoglycans have been reported. Analysis of lipoglycans involves the study of two parameters: intact molecules and carbohydrate parts. The conjunction of capillary electrophoresis and mass spectroscopy not only enhances the detection sensitivity, but also provides structural information on these structurally complex molecules. The interest in the field is rising and the results from the exact determination on the lipoglycan structure are expected to improve our understanding of the molecular mechanism of lipoglycan binding to proteins and cells of host organisms as well as their relationship to the virulence and pathogenesis of bacteria. In this report, an overview of the capillary electrophoresis methods used to analyze and characterize the intact lipoglycans as well as their carbohydrate parts is presented.

Capillary electrochromatography with novel stationary phases. IV. Retention behavior of glycosphingolipids on porous and non-porous octadecyl sulfonated silica

In this investigation, capillary electrochromatography (CEC) with a novel stationary phase proved useful for the separation of neutral and acidic glycosphingolipids (GSLs). Four different gangliosides, namely G(M1a), G(D1a), G(D1b) and G(T1b), served as the acidic GSLs model solutes. The following four GSLs: galactosylceramide (GalCer), lactosylceramide (LacCer), globotriaosylceramide (Gb3Cer) and globotetraosylceramide (Gb4Cer) served as the typical neutral GSLs. The stationary phase, octadecyl sulfonated silica (ODSS), consisted of octadecyl functions bonded to a negatively charged layer containing sulfonic acid groups. Porous and non-porous ODSS stationary phases were examined. The retention behavior of the acidic and neutral GSLs was examined over a wide range of elution conditions, including the nature of the electrolyte and organic modifier and the pH of the mobile phase. The porous ODSS stationary phase yielded the separation of the four different gangliosides using a hydro-organic eluent of moderate eluent strength whereas the non-porous ODSS stationary phase permitted the separation of the four neutral GSLs with a mobile phase of relatively high eluent strength.

High-performance liquid-phase separation of glycosides. III. Determination of total glucosinolates in cabbage and rapeseed by capillary electrophoresis via the enzymatically released glucose

A selective and sensitive method for the determination of total glucosinolates (GSs) in plant extracts by capillary electrophoresis-laser-induced fluorescence (LIF) detection was developed. It was based on the enzymatically released glucose from glucosinolates in the presence of the hydrolyzing enzyme myrosinase. The released glucose was converted to gluconic acid (GA) by the action of glucose oxidase. The resulting GA was then labeled selectively with the fluorescent tag 7-aminonaphthalene-1, 3-disulfonic acid (ANDSA). The peak area resulting from the GA-ANDSA derived from free and bound glucose was subtracted from the peak area of the GA-ANDSA resulting from the free glucose in the sample. This gave the total glucosinolates in the sample. The peak areas were normalized to the internal standard, N-acetylneuraminic acid derivatized with ANDSA. The method was validated using four different plant extracts, white cabbage leaves, rapeseed leaves, rapeseed roots, and rapeseed seeds. Furthermore, a capillary electrophoresis-UV detection method for profiling GS in plant extracts was developed. In addition to providing a fingerprint of the glucosinolates in plant extracts, the method allowed the experimenter to rapidly check the various steps involved in the extraction and sample cleanup.

A tabulated review of capillary electrophoresis of carbohydrates

This review summarizes publications on capillary electrophoresis (CE) of carbohydrates, covering almost all hitherto published papers on this topic. It is designed to be a convenient tool for the literature search by providing a comprehensive table. Since CE analysis of carbohydrates is generally complicated due to the structural diversity of carbohydrate species, an attempt is made in this table to supply detailed information on the analyzed form (underivatized or derivatized, type of derivative) and analytical conditions (capillary size, state of the inner wall, composition of the electrophoretic solution, applied voltage, detection method, etc.), for each combination of carbohydrate species to be analyzed. In addition, a brief overview is presented to help in the literature search.

Separation of chiral compounds by capillary electrophoresis

This review presents the different chiral selectors used in capillary electrophoresis (CE) for the separation of enantiomers. The use of charged cyclodextrins, crown ethers, polysaccharides, proteins, natural and synthetic micelles, macrocyclic antibiotics and ergot alkaloids is discussed in detail. Neutral native and derivatized cyclodextrins are not treated because several review articles have already been published on this topic. Recent developments like the application of two chiral selectors in the same background electrolyte are highlighted.

Derivatization in capillary electrophoresis

In recent years capillary electrophoresis (CE) has been developed into a versatile separation technique, next to gas and liquid chromatography (LC), well suited for the determination of a wide variety of e.g., pharmaceutical, biomedical and environmental samples. The main advantages of CE over chromatographic separation techniques are its simplicity and efficiency. It is well recognized, however, that the sensitivity and selectivity of the detection are relatively weak points of CE. One way to overcome these limitations is the conversion (derivatization) of the analytes into product(s) with more favourable detection characteristics. Although, in principle, almost any detection mode can be combined with a derivatization procedure, in practice, fluorescence monitoring is favoured in most cases. This paper aims to give a short overview on the various reagents that can be used for pre-, post- and on-column derivatization in CE. First, a short introduction is given on CE as an analytical technique, followed by a discussion of the pros and cons of the various modes of derivatization, a comparison of derivatizations in CE with derivatizations in LC, the principles of fluorescence and prerequisites for a good fluorophore and the potential of using diode lasers in combination with a labelling procedure. With respect to the derivatization reagents the emphasis is on the labelling of amino, aldehyde, keto, carboxyl, hydroxyl and sulfhydryl groups.

Capillary electrophoresis of carboxylated carbohydrates. IV. Adjusting the separation selectivity of derivatized carboxylated carbohydrates by controlling the electrolyte ionic strength at subambient temperature and in the absence of electroosmotic flow

The effect of the ionic strength of the running electrolyte on selectivity and resolution of 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) derivatives of carboxylated monosaccharides and sialooligosaccharides derived from gangliosides was evaluated in capillary electrophoresis in the absence of electroosmotic flow and at subambient temperature. The acidic saccharides used in this study were derivatized with ANDSA fluorescing tag to facilitate their detection by laser-induced fluorescence. To maximize resolution among the derivatized saccharides, commercially available fused-silica capillaries with 'zero' electroosmotic flow having polyvinyl alcohol coating on their inner walls were used as the separation capillaries. The effective electrophoretic mobility (mu) of the various ANDSA derivatized mono- and oligosaccharides decreased linearly with the inverse of the square root of the buffer concentration (1/square root of C) used in the running electrolyte. The extent of screening of the charge on the solute by the electrolyte counterions varied among the various saccharides as was manifested by the slopes of the lines of mu vs. 1/square root of C. Increasing the ionic strength of the running electrolyte allowed, via its charge screening effect, the modulation of selectivity thus adjusting the resolution of closely related saccharides.

Pre-, on- and post-column derivatization in capillary electrophoresis

This survey gives a short overview of the various reagents and procedures that can be used for pre-, post- and on-column derivatization in capillary electrophoresis. First there is an introduction about capillary electrophoresis as an analytical technique; this is followed by a discussion of the pros and cons of the various modes of derivatization and a comparison with liquid chromatography. In the following paragraphs the reagents for a number of functional groups are discussed. The emphasis is on derivatization of the amino group. Most of the information on the reagents and derivatization procedures is listed in tables together with information on the detection mode, analytes, sensitivity and samples. In addition to the amino group, information is given on labeling of aldehyde, keto, carboxyl, hydroxyl and sulfhydryl groups.

Recent developments in capillary electrophoresis of carbohydrate species

Carbohydrates are ubiquitous species involved in many life processes. Because of the multilateral roles of carbohydrates, their analysis has come to have increasing importance. As shown in this review, capillary electrophoresis in its various modes of operation has proved very useful in the analysis of carbohydrate species including mono- and oligosaccharides, glycoproteins, glycopeptides and glycosaminoglycans. Advances in separation approaches and applications as well as advances in detection including sensitive and selective pre-column derivatization are described. In summary, this comprehensive review is a supplement to previous reviews and covers the published work in 1996 and the first half of 1997.

Analysis of gangliosides by capillary zone electrophoresis and capillary zone electrophoresis-electrospray mass spectrometry

Gangliosides, sialic acid(s)-containing glycosphingolipids, were separated by capillary zone electrophoresis and detected with either UV or electrospray mass spectrometry. Several electrolyte system were evaluated for the separation of underivatized gangliosides. The best result was obtained by using 50 mM borate and 50 mM phosphate buffer containing 20 mM alpha-cyclodextrin at pH 9.9. The four major ganglioside forms (GM1, GD1a, GD1b, GT1b) were successfully separated, and, moreover, each ganglioside yielded two peaks, splitting by the difference in chain length of the ceramide moiety. The resolution obtained in CE-UV could not be reproduced in CE-MS because of the incompatibility of the borate/phosphate buffer to ESI-MS. With the use of more volatile buffers, such as ammonium acetate or 2-[N-cyclohexylamino]-ethanesulfonic acid, baseline resolution was obtained for gangliosides having different number of sugars, but the two disialoganglioside isomers, GD1a and GD1b, were coeluted.

Capillary electrophoresis of pesticides: V. Analysis of pyrethroid insecticides via their hydrolysis products labeled with a fluorescing and UV absorbing tag for laser-induced fluorescence and UV detection

Some representative standard pyrethroid insecticides, namely permethrin, phenotrin, cypermethrin, sanmarton and fenpropathrin, were subjected to base hydrolysis with the aim of facilitating the indirect determination of these neutral species of low water solubilities by aqueous capillary electrophoresis. This first involved the base fragmentation of the pyrethroids in alcohol buffer (pH 12.0), and then the selective tagging of the carboxylated hydrolytic products with 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) via a condensation reaction in the presence of organic soluble carbodiimide. The tagging of the hydrolytic products with ANDSA imparted each of the derivatives with two strong sulfonic acid groups whose permanent charges were necessary for achieving aqueous capillary electrophoresis. In addition, the labeling with ANDSA allowed the detection of the derivatives at low levels by capillary electrophoresis laser-induced fluorescence. The geometric and optical isomers of the ANDSA derivatives of the pyrethroid hydrolytic products were best separated when using electrolyte systems composed of sodium phosphate buffer, pH 6.5, containing n-octylglucoside chiral surfactant in the presence of small amounts of acetonitrile (e.g., 10% v/v).

Capillary electrophoresis of herbicides: IV. Evaluation of octylmaltopyranoside chiral surfactant in the enantiomeric separation of fluorescently labeled phenoxy acid herbicides and their laser-induced fluorescence detection

A novel chiral nonionic surfactant, namely octyl-b-D-maltopyranoside (OM), was evaluated in chiral capillary electrophoresis of fluorescently labeled phenoxy acid herbicides. The labeling of the analytes with 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) permitted a concentration detection limit of 5 x 10-10 M using laser-induced fluorescence detection. This limit of detection allowed the determination of ultradiluted solutions of the ANDSA-derivatized phenoxy acid herbicides whose concentration was a low as 10-11 M (i.e. 2.2 ppt) by applying the concept of field-amplified sample stacking (FASS). The sample injection by FASS did not adversely affect separation efficiencies, resolution and reproducibility of the electrophoretic system. The tagging of the phenoxy acid herbicides with ANDSA increased the hydrophobicity of the analytes, thus favoring an enhanced solubilization of the derivatized herbicides in the OM micellar phase. The net results of this effect were a much shorter analysis time and an improved enantiomeric resolution of the derivatives when compared to underivatized phenoxy acid herbicides. The optimum surfactant concentration required for maximum resolution decreased with increasing hydrophobicity of the analyte, with the least hydrophobic analyte requiring higher surfactant concentration. Because of the two permanently charged sulfonic acid groups of the ANDSA tag, the pH of the running electrolyte had little effect on the enantiomeric resolution of the derivatized herbicides. Due to its salting-out effect and increasing the micellized surfactant concentration, increasing the ionic strength of the running electrolyte increased the enantiomeric resolution of the least hydrophobic analytes. Conversely, increasing the percent methanol in the running electrolyte decreased the enantiomeric resolution of the least hydrophobic analytes due to a decrease strength of solute-micelle association. For hydrophobic analytes, existed an optimum percent of methanol existed for maximum enantiomeric resolution.

Capillary electrophoresis of carboxylated carbohydrates. Part 2. Selective precolumn derivatization of sialooligosaccharides derived from gangliosides with 7-aminonaphthalene-1,3-disulfonic acid fluorescing tag

The most suitable conditions for selective precolumn derivatization of sialooligosaccharides, derived from gangliosides, with 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) and the subsequent separation of the derivatives by capillary electrophoresis are described. ANDSA-sialooligosaccharide derivatives, which fluoresce at 420 nm when excited at 315 nm, were readily detected in capillary electrophoresis using an on-column lamp-operated fluorescence detector. In addition, the precolumn derivatization described here, which exploited the reactivity of the carboxylic acid group of the sialic acid residue of the oligosaccharides, replaced each weak carboxylic acid group of the parent sugar by two strong sulfonic acid groups. This allowed for electrophoresis over a wide range of pH and improved the resolution of the derivatives when compared to those obtained with underivatized sialooligosaccharides under identical separation conditions. The separation of sialooligosaccharides was best achieved when 75 mM borate, pH 10.0, was used as the running electrolyte. The derivatization and separation conditions described herein are expected to be readily transposed to the capillary electrophoresis of other sialooligosaccharides such as those derived from glycoproteins.

Fused-silica capillaries with surface-bound dextran layer crosslinked with diepoxypolyethylene glycol for capillary electrophoresis of biological substances at reduced electroosmotic flow

This report is concerned with the introduction of novel surface modification involving the covalent attachment of branched, high molecular weight dextrans and subsequent crosslinking with polyether chains on the inner surface of fused silica capillaries with the aim of producing hydrophilic capillaries with reduced electroosmotic flow (EOF). Three different molecular mass dextrans, namely 45, 71 or 150 kDa were covalently attached to the capillary surface, and subsequently crosslinked with diepoxypolyethylene glycol (PEG). This chemistry produced stable coating over a wide range of conditions including high and low pH aqueous solutions. Moreover, the various dextran-PEG-coated capillaries exhibited reduced electroosmotic flow. These features of the dextran-PEG coatings were useful for the separations of basic and acidic proteins, and provided high resolution separation for closely related acidic monosaccharides and sialooligosaccharides.