Analysis of underivatized cellodextrin oligosaccharides by capillary electrophoresis with direct photochemically induced UV‐detection

Abstract

Analysis of underivatized cellodextrin oligosaccharides by capillary electrophoresis with direct photochemically induced UV-detectionThis work focuses on the development of a CE method allowing, for the first time, the simultaneous separation of the underivatized first seven cellodextrin oligomers (glucose, cellobiose, cellotriose, cellotetraose, cellopentaose, cellohexaose, and celloheptaose), with a view to analyze the hydrolysates obtained after partial acid depolymerization of nitrocellulose, and eight carbohydrates (ribose, xylose, fructose, mannose, galactose, maltose, lactose, and sucrose), which might be potential interfering compounds in explosives samples. Separation was achieved with a highly alkaline BGE containing sodium chloride and direct mid-UV-absorbance detection was performed after photo-oxidation in the detection window. EOF was reversed to speed up the analysis using a dynamic capillary coating by hexadimethrine bromide. A central composite design was carried out to determine the effects of BGE conductivity and sodium hydroxide concentration on resolutions between neighboring peaks, and analysis time. A desirability analysis on modeled responses was applied to maximize resolutions and to minimize analysis time. The simultaneous analysis in 20 min total runtime of the 15 carbohydrates plus internal reference (naphthalene sulfonate) was carried out at 25°C with a BGE composed of 77.4 mM NaOH and 183 mM NaCl to adjust the conductivity at the optimum value. Finally, the resolution robustness was checked. This new method should also be of interest to monitor food and nonfood crop products. Keywords:Cellodextrins / Capillary electrophoresis / Design of experiments / Direct UV detection / Oligosaccharide DOI 10.1002/elps.201400605Additional supporting information may be found in the online version of this article at the publisher's web-site IntroductionCarbohydrates are ubiquitous compounds in the living world, as natural and degradation products, metabolites, or conjugates. They are also widely used as food or beverage additives. This class of compounds of tremendous complexity actually encompasses a variety of molecules differing in size (mono-, oligo-, and polysaccharides), epimerization or isomerization, glycosidic linkage, branching, and functionality , and mixed modes [11,13] have all been commonly employed. Separations have been based on hydrogen bonding, size, complexing ability, and in some cases charge. As far as detection is concerned, great difficulties are encountered due to the lack of a chromophoric moiety. According to the sensitivity requirements and separation mode, different detection strategies have been implemented, namely, without-or with pre-or postcolumn

Capillary electrophoresis as a method to determine underivatized urinary lipoarabinomannans, a biomarker of active tuberculosis caused byMycobacterium tuberculosis

“…It is still unknown whether the reaction is initiated by hydroxyl or superoxide radicals or something else, but most probable, the main intermediate responsible for the absorbance is malonenolate under alkaline conditions . Our research yielded similar results on the selectivity of large molecules to those in the literature for underivatized cellodextrin oligomers (glucose, cellobiose, cellotriose, cellotetraose, cellopentaose, cellohexaose, and celloheptaose) and correlated well with those published for cellohexaose and cellodextrin oligomers .…”

“…Recently, the CE separation along with direct UV detection of underivatized mono‐ and disaccharides has been demonstrated under highly alkaline electrolyte solution providing both carbohydrate ionization (p K a 12–13) and photo‐oxidation of the analytes into UV‐absorbing intermediates formed in the detection window . It is still unknown whether the reaction is initiated by hydroxyl or superoxide radicals or something else, but most probable, the main intermediate responsible for the absorbance is malonenolate under alkaline conditions . Our research yielded similar results on the selectivity of large molecules to those in the literature for underivatized cellodextrin oligomers (glucose, cellobiose, cellotriose, cellotetraose, cellopentaose, cellohexaose, and celloheptaose) and correlated well with those published for cellohexaose and cellodextrin oligomers .…”

“…For the first time, the CE separations in the three most alkaline electrolytes are also presented about the simultaneous separation of the underivatized cello‐, manno‐, and xylooligosaccharides using their mixture for optimization. The reactions in the presence of electric field in alkaline solution correlated well with those published for cellohexaose and cellodextrin oligomers . On the contrary, the inorganic ion markers chloride, sulfate, nitrate, and hydrogen phosphate used in the indirect UV method were studied earlier .…”

Investigation of photochemical reaction products of glucose formed during direct UV detection in CE

“…By now, the phenomenon is ascribed to a fast base catalyzed photochemical reaction in the detection window of the separation capillary resulting in the formation of substances that exhibit UV absorption in the mentioned region . The applicability of this novel method of saccharide detection in CE has been demonstrated in various matrices . Other investigations dealt with the underlying photochemical reaction itself .…”

Recent advances in capillary electrophoresis separation of monosaccharides, oligosaccharides, and polysaccharides

“…Recently, a novel method for the separation of underivatized cellodextrin oligosaccharides by CE with direct photochemically induced UV detection has been proposed by Alinat et al . They reported the simultaneous analysis of 15 carbohydrates in a 20 min total runtime, carried out at 25°C with a BGE composed of 77.4 mM NaOH and 183 mM NaCl to adjust the conductivity at the optimum value (Fig.…”