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 tR vs. number of glucose residues (nGlc) 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.

Internal hernia as a complication of congenital falciform ligament window.

Commonly, small bowel obstruction (SBO) is caused by either postoperative adhesions or external hernias. Internal hernias are rare, accounting for less than 2% of all cases of intestinal obstruction. An internal hernia through the falciform ligament is extremely uncommon and is usually secondary to a congenital or iatrogenic defect caused by trocars insertion. In this article, we report a case of SBO in a virgin abdomen that appeared to be caused by a congenital defect in the falciform ligament. A search of the literature was done identifying all reported cases of internal hernias caused by falciform ligament defect in order to guide diagnosis and management as well as avoidance of hernias caused by iatrogenic defects.

Determination of cellular carbohydrates in peanut fungal pathogens and baker's yeast by capillary electrophoresis and electrochromatography.

In this work, the quantitation of cellular carbohydrates, namely chitin and glucan, in peanut fungal pathogens and baker's yeast was carried out by capillary electrophoresis (CE) and capillary electrochromatography (CEC). The chitin and glucan of the fungi were hydrolyzed by the enzymes chitinase and glucanase, respectively, to their corresponding sugar monomers N-acetylglucosamine (GlcNAc) and glucose (Glc). These two monosaccharides were then tagged with 6-aminoquinoline (6-AQ) to allow their separation and detection in CE and CEC. The 6-AQ derivatives of GlcNAc and Glc formed the basis for the determination by CE and CEC of chitin and glucan in peanut fungi and baker's yeast. Several parameters affecting the separation of the 6-AQ derivatives of GlcNAc and Glc, including the separation voltage and the composition of the running electrolyte, were investigated. Under the optimized separation conditions, the contents of cellular carbohydrates including N-acetylglucosamine, chitin, glucose, and glucan in some fungi, such as Sclerotinia minor, Sclerotium rolfsii, and baker's yeast, were successfully determined. The method described here allowed the assessment of genetic differences in Sclerotium rolfsii isolates from various locations.

Capillary electrochromatography with polyacrylamide monolithic stationary phases having bonded dodecyl ligands and sulfonic acid groups: evaluation of column performance with alkyl phenyl ketones and neutral moderately polar pesticides.

In this report, we describe the preparation of porous polyacrylamide-based monolithic columns via vinyl polymerization. These monoliths possess in their structures bonded dodecyl ligands and sulfonic acid groups. While the sulfonic acid groups are meant to support the electroosmotic flow (EOF) necessary for moving the mobile phase through the monolithic capillary, the dodecyl ligands are introduced to provide the nonpolar sites for chromatographic retention. However, incorporating the sulfonic acid groups in the monoliths does not only support the EOF but also exhibit hydrophilic interaction with moderately polar compounds such as urea herbicides and carbamates insecticides. Consequently, mixed-mode (reversed-phase/normal phase) retention behavior is observed with neutral and moderately polar pesticides. The amount of sulfonic acid group in the monolith can be conveniently adjusted by changing the amount of vinylsulfonic acid added to the polymerization reaction. Optimum EOF velocity and adequate chromatographic retention are obtained when 15% vinylsulfonic acid is added to the reaction mixture. Under these conditions, rapid separation and high plate counts reaching greater than 400000 plates/m are readily obtained.

Electrically driven microseparation methods for pesticides and metabolites: V. Micellar electrokinetic capillary chromatography of aniline pesticidic metabolites derivatized with fluorescein isothiocyanate and their detection in real water at low levels by laser-induced fluorescence.

Anilines are important pollutants occurring in the environment as industrial discharges as well as the transformation products (i.e., metabolites) of a wide variety of commonly used pesticides. In this report, we describe the precolumn derivatization of anilines with fluorescein isothiocyanate (FITC) and their subsequent separation and detection by capillary electrophoresis-laser induced fluorescence (CE-LIF) detection. The FITC-aniline derivatives were readily detected at the 10(-10) M level. This limit of detection (LOD) was achieved in the presence of glycosidic surfactants complexed with borate at alkaline pH yielding the so-called in situ charged micelles. The glycosidic surfactants evaluated were n-octyl- and n-nonylglucopyranoside. Furthermore, and under optimum conditions, the FITC precolumn derivatization of the anilines was performed in real water (e.g., tap and lake water) spiked with anilines at the LOD level. The water matrices showed marginal effects on the extent of derivatization at the LOD level, and the possible interferents in the water samples did not affect the FITC-solute signal due to the selectivity of the derivatization and detection schemes. Besides filtration from microparticles, the real water samples did not necessitate extensive sample cleanup prior to derivatization.

Electrically driven microseparation methods for pesticides and metabolites: VI. Surfactant-mediated electrokinetic capillary chromatography of aniline pesticidic metabolites derivatized with 9-fluoroenylmethyl chloroformate and their detection by laser-induced fluorescence.

In this report, we describe a surfactant-mediated electrokinetic capillary chromatography (SM-EKC) system for the separation of 9-fluoroenylmethyl chloroformate (FMOC)-derivatized anilines by capillary electrophoresis (CE). The SM-EKC system consisted of dioctyl sulfosuccinate (DOSS)/acetonitrile mixtures and was suited for the CE separation of the relatively hydrophobic FMOC-aniline analytes and other neutral compounds, e.g. alkylphenyl ketones. While the organic modifier acetonitrile (ACN) allowed the solubilization of the hydrophobic solutes and maintained the DOSS surfactant in its monomeric form by inhibiting micellization, the DOSS surfactant associated with the FMOC anilines to a varying degree thus leading to their differential migration and separation. Under these conditions, the FMOC-anilines were readily detected at the 10(-6) M level by UV at 214 nm and at the 10(-8) M level by laser-induced fluorescence (LIF) using a solid-state UV laser operating at 266 nm line as the excitation wavelength. The FMOC precolumn derivatization was also readily performed in lake water spiked with anilines at near the limit of detection (LOD) level. The lake water matrix showed no significant effects on the extent of derivatization at the LOD level as well as on the detection of the analytes due to the selectivity of the FMOC derivatization. The derivatization and detection of spiked lake water necessitated only the removal of microparticles by microfiltration prior to derivatization and detection.

On-column trace enrichment by sequential frontal and elution electrochromatography. 1. Application to carbamate insecticides.

An on-column trace enrichment method for CEC of dilute samples is presented. The method involves on-line preconcentration by frontal electrochromatography under conditions of strong solute binding to the stationary phase followed by a step-gradient elution electrochromatography with a mobile phase of high eluting strength. This method is tested with dilute samples of carbamate insecticides using capillary columns of 100-microm i.d. packed with a 5-microm octadecyl silica (ODS) stationary phase. The effectiveness of on-line preconcentration (i.e., zone narrowing) depends on the retention factor, k', of the analyte in the injection solvent as well as in the eluting mobile phase (i.e., the organic solvent content), the applied voltage during sample introduction, and elution and length of the introduced sample plug. Under optimal frontal and elution electrochromatography conditions, a 500-fold sensitivity increase is achieved for carbofuran (a carbamate insecticide) with a UV detector. The method is demonstrated with deionized and tap water samples spiked with carbamate insecticides.

Capillary electrophoresis and electrochromatography of pesticides and metabolites.

Synthetic pesticides are important chemicals since they are widely used to control many types of weeds, insects, and other pests in a wide variety of agricultural and nonagricultural settings. This review article is aimed at describing the recent progress made in capillary electrophoresis (CE) and capillary electrochromatography (CEC) of pesticides and metabolites. The various electrophoretic systems and detection schemes that were introduced during the period extending from the second half of 1999 to the first half of 2001 for the CE and CEC of pesticides are discussed. Also included in this review article are the various approaches for trace enrichment that are involved in the analysis of dilute pesticide samples.

Enantiomeric separation by capillary electrochromatography. I. Chiral separation of dansyl amino acids and organochlorine pesticides on a diol-silica dynamically coated with hydroxypropyl-beta-cyclodextrin.

In this work, a commercially available diol-silica stationary phase was converted in situ to a chiral stationary phase by dynamically coating it with hydroxypropyl-beta-cyclodextrin (HP-beta-CD). This stationary phase was shown useful for the capillary electrochromatography (CEC) separation of neutral and anionic enantiomers such as some organochlorine pesticides and dansyl amino acids, respectively. The inclusion of HP-beta-CD in the mobile phase to produce the in situ chiral stationary phase allowed the rapid separation of the anionic dansyl amino acid enantiomers at relatively low electroosmotic flow (EOF). The formation of host-guest complexes between the dansyl amino acids and the neutral HP-beta-CD in the mobile phase lowered the actual charge-to-mass ratios of the anionic solutes, thus speeding up their transport by the EOF across the packed capillary column. Several parameters affecting enantioseparation were investigated, including the concentration of HP-beta-CD, ionic strength, pH, and organic modifier content of the mobile phase.

Enantiomeric separation by capillary electrochromatography. II. Chiral separation of dansyl amino acids and phenoxy acid herbicides on sulfonated silica having surface-bound hydroxypropyl-beta-cyclodextrin.

A chiral silica-based stationary phase having surface-bound hydroxypropyl-beta-cyclodextrin (HP-beta-CD) with a relatively strong electroosmotic flow (EOF) was introduced for enantioseparation by capillary electrochromatography (CEC). The stationary phase contained a hydrophilic sulfonated sublayer to which a chiral top layer of HP-beta-CD was immobilized. While the sulfonated sublayer was to provide a relatively strong EOF, the top HP-beta-CD was to confer the desired chiral recognition towards enantiomeric solutes. This HP-beta-CD sulfonated silica (CDSS) stationary phase proved useful for the rapid separation of anionic enantiomers such as dansyl amino acids and phenoxy acid herbicides. The effects of the organic modifier content, pH, and ionic strength of the mobile phase on enantioseparation were investigated. Under the optimized separation conditions, ten dansyl amino acids and six phenoxy acid herbicides were enantioseparated with a resolution greater than unity.

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.

Electrically driven microseparation methods for pesticides and metabolites: III. Capillary electrochromatography with novel silica-based stationary phases having a surface-bound surfactant moiety.

A silica-based stationary phase with surface bound silylpropyl trialkylammonium functions was introduced and evaluated in the capillary electrochromatography of alkylbenzenes and pesticides. This stationary phase is referred to as octadecyldimethyl(3-trimethoxysilylpropyl) ammonium-silica (ODAS) and has quaternary amine functions that generate an anodic electroosmotic flow (EOF) and octadecyl functions that are responsible for solute retention by a reversed-phase chromatography mechanism. The ODAS stationary phase was characterized over a wide range of elution conditions in term of EOF and retention behavior of alkylbenzene homologous series. The ODAS stationary phase proved useful in the separation of pesticides as well as in the on-column preconcentration of dilute pesticide samples, thus permitting the detection of solution at 7 x 10(-7) M using a UV detector.

Electrically driven microseparation methods for pesticides and metabolites: IV. Effects of the nature of fluorescent labels on the enantioseparation of pesticides and their degradation products by capillary zone electrophoresis with UV and laser-induced fluorescence detection.

Three different fluorescent tags, namely 5-aminonaphthalene-1-sulfonic acid (ANSA), 7-aminonaphthalene-1,3-disulfonic acid (ANDSA), and 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS) were evaluated in the precolumn derivatization of some chiral phenoxy acid herbicides, some chiral transformation products of pyrethroid insecticides, and in their subsequent enantiomeric separation by capillary electrophoresis (CE). The electrolyte systems consisted of sodium phosphate buffers containing chiral surfactants such as octylglucoside (OG) or octylmaltoside (OM) at concentrations above the critical micellar concentration (CMC). Among the three different tags investigated, the ANDSA derivatives of the various solutes were more readily enantioseparated than the ANSA and ANTS derivatives. While the tagging with ANSA allowed the enantioseparation of a limited number of the chiral solute-ANSA derivatives investigated, the ANTS derivatization yielded derivatives that could not be enantioseparated. The polarity of the three different tags increases by increasing the number of sulfonic acid groups in the molecule in the following order: ANSA (one sulfonic acid) < ANDSA (two sulfonic acid groups) < ANTS (three sulfonic acid groups). This seems to indicate that the intermediate polarity of the ANDSA tag allowed more equitable nonpolar/polar interactions of the ANDSA-derivatized solutes with the OG or OM micelles, and consequently the enantioseparation of the solute-ANDSA derivatives. Thus, there is a solute polarity window for enantioresolution with alkylglycoside micelle by CE. Solutes of intermediate polarity that undergo more equitable nonpolar/polar interactions with the micelles exhibited chiral separations.

Chiral glycosidic surfactants for enantiomeric separation in capillary electrophoresis.

Several glycosidic surfactants (GSs) have been shown useful in the separation of enantiomers by capillary electrophoresis. The virtue of GSs is that they can be used as (i) neutral chiral additives in the running electrolyte for the enantioseparation of charged chiral solutes by capillary zone electrophoresis, (ii) as in situ charged micelles for the enantioseparation of neutral and charged chiral solutes by micellar electrokinetic capillary chromatography (MECC), (iii) as anionic chiral surfactants in the MECC mode upon covalently attaching negatively charged groups to their sugar head groups, and (iv) as neutral and anionic chiral surfactants mixed with achiral micelles (e.g., sodium dodecyl sulfate) for MECC of enantiomers. This review article is to provide a comprehensive description of GSs in the chiral separation of various enantiomers over a wide range of operating conditions.

Recent developments in capillary electrophoresis and capillary electrochromatography of carbohydrate species.

This review article is concerned with the recent developments in capillary electrophoresis (CE) and capillary electrochromatography (CEC) of carbohydrates. The literature shows that CE possesses impressive potential in the analysis of carbohydrates. On the other hand, CEC has just started to show promise in the analysis of carbohydrates. Advances in separation and detection approaches of derivatized and underivatized carbohydrates are discussed based on the available literature. In addition, important applications are illustrated.

Capillary electrophoresis of glucosinolates and their degradation products.

Glucosinolates are important natural products occurring mainly in plants of the Cruciferae family. This review article is aimed at describing the recent progress made in capillary electrophoresis of glucosinolates and their degradation products. It describes the various electrophoretic systems and detection schemes introduced to date for the capillary electrophoresis (CE) of glucosinolates and their degradation products. Also included in this review are the applications of CE to the qualitative and quantitative determination of glucosinolates and their degradation products in plant extracts.

High-performance liquid phase separation of glycosides. 5. Determination of individual glucosinolates in cabbage and rapeseed by laser-induced fluorescene capillary electrophoresis via the enzymatically released isothiocyanate aglycon.

A capillary electrophoresis (CE) method was developed for the profiling and determination of individual glucosinolates (GSs) via their isothiocyanate degradation products upon myrosinase digestion. The resulting isothiocyanates, the structures of which are reflective of the parent GS's, were then converted to their corresponding amines via base hydrolysis or reaction with 1, 2-benzenedithiol. Subsequently, the amines were fluorescently labeled to allow their sensitive detection by laser-induced fluorescence (LIF). The CE method involved the use of in situ charged micelles for the separation of isothiocyanates and their corresponding fluorescently labeled amines by micellar electrokinetic capillary chromatography (MECC). The term "in situ charged micelles" refers to micelles formed by complexing the polar hydroxyl groups of glycosidic surfactants with borate. The MECC method with on-column LIF detection was applied to the determination of GSs in white cabbage, rapeseed leaves, and rapeseed roots.

Capillary electrophoresis and electrochromatography of pesticides and metabolites.

Synthetic pesticides are important chemicals since they are widely used to control many types of weeds, insects and other pests in a wide variety of agricultural and nonagricultural settings. This review article is aimed at describing the recent progress made in capillary electrophoresis (CE) and capillary electrochromatography (CEC) of pesticides and their metabolites. The various electrophoretic systems and detection schemes that have been introduced so far for the CE and CEC of pesticides are discussed. Also included in this review article are the various approaches for trace enrichment that are involved in the analysis of dilute pesticide samples.

Enantioseparations by capillary electrophoresis using chiral glycosidic surfactants. I. Evaluation of cyclohexyl-pentyl-beta-D-maltoside surfactant.

Chiral cyclohexyl-pentyl-beta-D-maltoside (CYMAL-5) surfactant was evaluated in the enantioseparation of charged racemic species by capillary electrophoresis. CYMAL-5 is a glycosidic surfactant (GS) with a chiral maltose polar head group and a cyclohexyl-pentyl hydrophobic tail. At concentrations above its critical micellar concentration (CMC), CYMAL-5 produces neutral micelles in aqueous media. The neutral micelles migrate at the velocity of the electroosmotic flow (EOF). As expected, the CYMAL-5 system was only useful for the enantioseparation of charged chiral solutes. The enantioresolution of the CYMAL-5 can be manipulated over a wide range of electrolyte composition, e.g., pH, ionic strength and surfactant concentration. In the presence of EOF, and in all cases, there is an optimum surfactant concentration for maximum enantioresolution, which is located at low surfactant concentration for strongly hydrophobic solutes and at high surfactant concentration for relatively hydrophilic solutes. The presence of an optimum surfactant concentration for maximum enantioresolution is attributed to the EOF. At low pH values where the EOF is negligible, enantioresolution increased with increasing surfactant concentration in the useful concentration range in a way similar to chromatography.