Published: August 01, 2011 r2011 American Chemical Society 7381 dx.doi.org/10.1021/ac2012834 | Anal. Chem. 2011, 83, 7381–7387 ARTICLE pubs.acs.org/ac New Avenue for Mid-UV-Range Detection of Underivatized Carbohydrates and Amino Acids in Capillary Electrophoresis C  edric Sarazin, †,‡,§,^ Nathalie Delaunay,* ,‡,§,^ Christine Costanza, † V  eronique Eudes, † Jean-Maurice Mallet, §,||,# and Pierre Gareil ‡,§,^ † Central Laboratory of the Prefecture de Police, 39 bis, rue de Dantzig, 75015 Paris, France ‡ Chimie ParisTech, Laboratory of Physicochemistry of Electrolytes, Colloids and Analytical Sciences (PECSA), 75005 Paris, France § UPMC Univ Paris 06, 75005 Paris, France ^ CNRS, UMR 7195, 75005 Paris, France ) ENS, Laboratory of Biomolecules (LBM), 75005 Paris, France # CNRS, UMR 7203, 75005 Paris, France b S Supporting Information C arbohydrate analysis remains challenging, because of the great molecular diversity, the presence of several struc- tural isomers, and the lack of easy-to-implement and sensitive detection methods. Currently, methods used for the separa- tion of carbohydrates include thin-layer chromatography, 1 gas chromatography, 2,3 and liquid chromatography (LC). 4À6 Most often, LC methods used normal phase (HILIC), 7 reverse- phase, 8 or anion-exchange modes 8,9 with direct low-UV-range or refractive index detections 4 and most often mass spectrometry, ultraviolet (UV), or fluorescence detection after precolumn derivatization. 10À12 More recently, important developments were carried out with the coupling between high performance anion-exchange chromatography and pulsed-amperometric detection. 4,9 Currently, capillary electrophoresis (CE), with its high separa- tion efficiency, low reagent consumption, and speed, appears to be an interesting alternative to chromatographic methods, especially for sulfated and carboxylated carbohydrates, 4,12À16 but the analysis of so-called neutral carbohydrates can be more difficult to implement, because of the absence of easily ionizable functions (other than anomeric hydroxyl group) and chromo- phore groups (see Table S-1 in the Supporting Information), and the high hydrophilic character of these compounds, which makes the use of micelles inoperable. Different strategies are available to circumvent these different drawbacks. Complexation with borate anions at pH comprised between 8.0 and 10.0 has long been used in carbohydrate analysis and exploited in CE with direct UV detection at 195 nm; 17,18 however, this low wavelength does not favor selective detection, generates interferences, and suffers from poor sensitivity. As of today, the most widely used CE Received: May 27, 2011 Accepted: August 1, 2011 ABSTRACT: Capillary electrophoresis (CE) appeared as an interesting alternative to chromatographic methods for carbohydrate analysis, but it can be difficult to implement, because of the lack of easily ionizable functions and chromophore groups. Recently, a promising method was proposed by Rovio et al. for the CE separation under extremely high alkaline conditions of neutral carbohydrates under their alcoholate form and their direct UV detection [Rovio et al. Electrophoresis 2007, 28, 3129À3135; and Rovio et al. J. Chromatogr. A 2008, 1185, 139À144], which is claimed to be due to the absorption of enediolate at 270 nm. Even so, most of the detected compounds in Rovio’s paper (for example, sucrose) cannot give such enediolate, lacking a carbonyl group. In this work, a deeper insight was paid to the understanding of detection mechanism. In effect, unusual detection phenomena were observed in comparing reducing and nonreducing carbo- hydrate behaviors, which pointed to the existence of photochemical reactions in the detection window. A more systematic study of the influence of many parameters (carbohydrate nature, electrolyte pH, residence time in the detection window, and capillary diameter) was undertaken. In addition to this, most of this work was performed under cathodic (reversed) electro-osmotic flow conditions (using Polybrene-modified capillaries), to obtain much faster separations than under Rovio’s conditions. This study also opens up new avenues for the detection in mid-UV range of non-UV-absorbing compounds bearing reducing moieties, such as amino acids.