Determination of carbohydrates in fruit juices by capillary electrophoresis and high-performance liquid chromatography

Grapevine tissues and phenology differentially affect soluble carbohydrates determination by capillary electrophoresis

Soluble carbohydrates distribution depends on plant physiology and, among other important factors, determines fruit yield and quality. In plant biology, the analysis of sugars is useful for many purposes, including metabolic studies. Capillary electrophoresis (CE) proved to be a powerful green separation technique with minimal sample preparation, even in complex plant tissues, that can provide high-resolution efficiency. Matrix effect refers to alterations in the analytical response caused by components of a sample other than the analyte of interest. Thus, the assessment and reduction of the matrix factor is fundamental for metabolic studies in different matrices. The present study evaluated the source and levels of matrix effects in the determination of most abundant sugars in grapevine tissues (mature and young leaves, berries and roots) at two phenological growth stages. Sucrose was the sugar that showed the least matrix effects, while fructose was the most affected analyte. Based on plant tissues, young leaves presented the smaller matrix effects, irrespectively of the phenology. These changes may be attributed to considerable differences at chemical composition of grapevine tissues with plant development. Therefore, matrix effect should be an important concern for plant metabolomics.

Glucose: Detection and analysis

Glucose is an aldosic monosaccharide that is centrally entrenched in the processes of photosynthesis and respiration, serving as an energy reserve and metabolic fuel in most organisms. As both a monomer and as part of more complex structures such as polysaccharides and glucosides, glucose also plays a major role in modern food products, particularly where flavor and or structure are concerned. Over the years, many diverse methods for detecting and quantifying glucose have been developed; this review presents an overview of the most widely employed and historically significant, including copper iodometry, HPLC, GC, CZE, and enzyme based systems such as glucose meters. The relative strengths and limitations of each method are evaluated, and examples of their recent application in the realm of food chemistry are discussed.

Glycan labeling strategies and their use in identification and quantification

Most methods for the analysis of oligosaccharides from biological sources require a glycan derivatization step: glycans may be derivatized to introduce a chromophore or fluorophore, facilitating detection after chromatographic or electrophoretic separation. Derivatization can also be applied to link charged or hydrophobic groups at the reducing end to enhance glycan separation and mass-spectrometric detection. Moreover, derivatization steps such as permethylation aim at stabilizing sialic acid residues, enhancing mass-spectrometric sensitivity, and supporting detailed structural characterization by (tandem) mass spectrometry. Finally, many glycan labels serve as a linker for oligosaccharide attachment to surfaces or carrier proteins, thereby allowing interaction studies with carbohydrate-binding proteins. In this review, various aspects of glycan labeling, separation, and detection strategies are discussed.

Capillary electrophoresis of sugar acids

This chapter illustrates the usefulness of capillary electrophoresis (CE) for the analysis of sugar acids, that is, monosaccharides and lower oligosaccharides carrying carboxylate, sulphate or phosphate groups. In order to provide a general description of the main results and challenges in the field, some relevant applications and reviews on CE of such saccharidic compounds are tabulated. Furthermore, some detailed experimental procedures are shown, regarding the CE analysis of sugar acids released upon hydrolysis of acidic polysaccharides and of glycans linked to glycoproteins. In particular, the protocols will deal with the following compounds: (i) unsaturated, underivatized oligosaccharides from lyase-treated alginate; (ii) oligosaccharides derivatized with 4-aminobenzonitrile, arising from chemical hydrolysis of alginate; (iii) sialic acid derivatized with 2-aminoacridone, released from human serum immunoglobulin G.

Capillary electrophoresis of neutral carbohydrates: mono-, oligosaccharides, glycosides

This chapter reports an overview of the recent advances in the analysis of neutral sugars by capillary electrophoresis (CE); furthermore, some relevant reviews and research articles in the field are tabulated. Comparison of CE with chromatography is also presented, with special attention to separation efficiency and sensitivity. The main routes aimed at pretreatment and CE analysis of uncharged mono-, oligosaccharides, and glycosides are described. Representative examples of such procedures are reported in detail, upon describing robust methodologies for the study of (1) neutral mono- and oligosaccharides derivatized by reductive amination and by formation of glycosylamines; (2) underivatized mono- and di-saccharides analyzed using highly alkaline buffers; and (3) anomeric couples of glycosides separated using borate-based buffers.

Comparative evaluation of extraction procedures and method validation for determination of carbohydrates in cereals and dairy products by capillary electrophoresis

This work describes the development and application of two optimized electrolytes: 15 mmol/L sorbate, 0.2 mmol/L CTAB, and 35 mmol/L sodium hydroxide for the determination of fructose, glucose, maltose, maltotriose, and sucrose in cereals and 15 mmol/L sorbate, 0.3 mmol/L CTAB, and 55 mmol/L sodium hydroxide for the determination of fructose, glucose, galactose, lactose, and sucrose in dairy products. Both methods were validated with respect to linearity, limits of detection (using both signal-to-noise ratio and the Eurachem approach), recovery tests, and intra- and inter-day precision exhibiting adequate performance. Additionally, statistically similar results were obtained in a comparative study of extraction procedures for carbohydrates using the AOAC protocol, ultrasound extraction, magnetic stirring, and sample dissolution.

Simultaneous determination of glucose, fructose and lactose in food samples using a continuous-flow chemiluminescence method with the aid of artificial neural networks

In this study, a simple continuous-flow chemiluminescence (CL) system was developed for simultaneous determination of glucose, fructose and lactose in ternary mixtures of reducing sugars without previous separation. This method was based on the different kinetics of the individual sugars in the oxidation reaction with potassium ferricyanide. The known luminol-K(3)Fe(CN)(6) CL system was used to measure the kinetic data of the system. The CL intensity was measured and recorded every second from 1 to 300 s. The data obtained were processed chemometrically using an artificial neural network. The relative standard errors of prediction for three analytes were <5%. The proposed method was successfully applied to the simultaneous determination of the three sugars in some food samples.

Development of an Aerosol Chemiluminescent Detector Coupled to Capillary Electrophoresis for Saccharide Analysis

A novel aerosol chemiluminescent (CL) detector coupling to capillary electrophoresis (CE) for the detection of saccharides is reported. This CL detector is composed of a postcapillary nebulizer and porous alumina as catalyzer in quartz tube. The CL emission could be generated due to the catalyzing oxidization of saccharides on the surface of porous alumina. The saccharides such as sucrose, alpha-lactose, maltose, raffinose, galactose, xylose, and glucose with only weak UV absorbance can be successfully detected. The linear ranges of those saccharides are from 30-2000 to 50-2000 mg/L; relative standard deviations range from 2.1 to 3.7% (200 mg/L, n = 11). Compared with the traditional UV detector currently used in CE, this novel detector shows the advantage of high sensitivity to the compounds with only weak UV absorption. Thus, it could be an important supplement of CE detectors for UV-lacking compounds.

Capillary electrophoretic separation of sugars in fruit juices using on-line mid infrared Fourier transform detection

Fourier Transform infrared spectroscopy has been coupled to on-line capillary electrophoresis (CE) for the separation and detection of natural sugars in orange fruit juices. The CE separation electrolyte comprised 50 mM sodium carbonate buffer adjusted to pH 12.3 with NaOH. Galactose was selected as an internal standard. To ensure tight connections between the custom-made IR-transparent flow cell (optical path length was 15 [micro sign]m) and the fused silica capillaries, commercially available O-rings were used. The scanner of the spectrometer was operated at a HeNe laser modulation frequency of 320 kHz, recording interferograms in a double-sided, forward-backward mode with 8 cm(-1) spectral resolution. For each spectrum 64 interferograms (512 for the background) were co-added and a Blackman-Harris 3-term apodization function was performed. A low-pass filter at 1828 cm(-1) was inserted in the IR beam to increase the light throughput in the spectral region of interest (1800 cm(-1)-900 cm(-1)). Using these features a new spectrum could be obtained every two seconds. Sucrose, glucose and fructose were structurally identified and quantified in orange juice samples. The limits of detection (3S/N) for all analytes were in the low millimolar range (0.7-1.9 mM) or, in absolute amounts, the low nanogram range (1.5-3.2 ng). The resolution ranged between 1.14 to 3.15 and the RSD of the proposed method was 1.8-4.4%.

Comparative study between capillary electrophoresis and high performance liquid chromatography in ‘guarana’ based phytopharmaceuticals

The last years have seen a significant increase in the use of herbal medicines and their preparations all over the world. Adulterations with synthetic drugs are common problems with phytopharmaceutical products and this can potentially cause adverse effects. In consequence, it is important to determine the presence of synthetic drugs in herbal medicines to ensure their efficacy and safety. In this study, guarana derivatives were analyzed by capillary electrophoresis (CE), and the results were compared with those obtained by the HPLC technique. In order to obtain adequate fingerprints, and search for adulterants, caffeine was used as the marker compound. This separation method was applied to analyze the seed powder and commercial tablets of Paulinia cupana Mart. The methodology performance was evaluated in terms of specificity, sensitivity and precision. The results are in agreement with those obtained by the HPLC method. Furthermore, the analysis time of the CE method is up to two times shorter than the respective parameter in HPLC and solvent consumption is more than 100-fold less.

Chromatographic analysis of sugars applied to the characterisation of monofloral honey

The control of the floral quality of honey has become a priority issue as a result of the number of abuses observed and the relative ease of getting around existing control methods. We conducted chromatographic analyses of honey sugars to determine new criteria for authenticating an origin. The work involved creating databases by analysing a large number of authentic honeys from seven monofloral varieties, followed by statistical processing of the results by a principal components analysis. Differences in composition could thus be demonstrated, such as the presence of trisaccharides in fir honey, that provide an additional tool for authenticating unknown commercial honeys.

Application of carbohydrate analysis to verify honey authenticity

Gas chromatography and liquid chromatography have been used simultaneously to analyze sugars in honey. After statistical processing by principal components analysis, additions of exogenous sugars could be detected by the appropriate fingerprints of adulteration. Application to acacia, chestnut and lavender honeys enabled the detection of fraud resulting from 5 to 10% addition of sugar syrups. This method may be considered as a replacement of isotopic analysis, that has some limitations.

Determination of the artificial sweetener Sucralose by capillary electrophoresis

The artificial intense sweetener 1,6-dichloro-1,6-dideoxy-beta-D-fructofuranosyl-4-chloro-4-deoxy-alpha-D-galactopyranose (Sucralose) was determined by capillary electrophoresis with indirect ultraviolet absorption in a 3,5-dinitrobenzoic acid buffer at pH 12.1. The method allowed determination of Sucralose in low-calorie soft drinks, without any sample clean-up over a linear range of 42-1000 mg x l(-1) (r=0.9991). The limits of detection and determination were 28 and 42 mg x l(-1), respectively, and the repeatability for a mean concentration of 100 mg x l(-1) was 4.2% for the signal area and 3.6% for the migration time, which were deemed satisfactory for use in food control.

Enhancement of detection sensitivity for indirect photometric detection of anions and cations in capillary electrophoresis

This review focuses on the indirect photometric detection of anions and cations by capillary electrophoresis. Special emphasis has been placed on the sensitivity of the technique and approaches taken to enhance detection limits. Theoretical considerations and requirements have been discussed, including buffering, detection sensitivity, separation of cations, and detector linearity. A series of tables detailing highly absorbing probes and the conditions of their use for indirect photometric detection are included.

The determination of a potential impurity in Thalidomide drug substance and product by HPLC with indirect UV detection

Thalidomide molecule, a synthetic derivative of glutamine, can undergo hydrolysis at physiologic pH to form glutamine. Additionally, L-glutamine is one of the starting materials in the synthesis of Thalidomide drug substance. The current USP method for testing glutamine is thin-layer chromatography (TLC) with ninhydrin spray visualization. A more quantitative and automated high performance liquid chromatography (HPLC) method utilizing indirect ultraviolet (UV) detection was developed and validated for the determination of the non-UV absorbing glutamine in Thalidomide drug substance and product. The HPLC mobile phases consisted of phosphoric acid, 2-naphthalenesulfonate sodium and methanol. 2-Naphthalenesulfonate was used as a UV detection probe for glutamine. A segmented isocratic elution program was used to elute glutamine and Thalidomide, respectively. The method was found to be specific for glutamine. The linearity was 0.05-1.25% glutamine with respect to a nominal concentration of 8 mg ml(-1) Thalidomide sample. The limits of detection and quantitation were found to be 0.03 and 0.05% glutamine, respectively. The injection precision was 2.7% for area responses and 0.2% for the retention times. The recovery of glutamine at three concentration levels was found to be 100.8+/-2.8% from placebo and 99.2+/-5.8% from spiked Thalidomide drug substances. This newly developed HPLC method was used to determine glutamine in Thalidomide drug substances and products. The results from HPLC were in agreement with those from TLC. Therefore, the method developed is a suitable alternative to the current USP TLC procedure. Additionally, the method offers the advantage of being quantitative and automated.

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.

Determination of the composition of the oligosaccharide phosphate fraction of Pichia (Hansenula) holstii NRRL Y-2448 phosphomannan by capillary electrophoresis and HPLC

The promising new anticancer agent, PI-88, is prepared by the sulfonation of the oligosaccharide phosphate fraction of the extracellular phosphomannan produced by the yeast Pichia (Hansenula) holstii NRRL Y-2448. The composition of the oligosaccharide phosphate fraction was determined by capillary electrophoresis (CE) with indirect UV detection using 6 mM potassium sorbate at pH 10.3 as the background electrolyte. Further confirmation of the composition was obtained by HPLC analysis of a sample dephosphorylated by treatment with alkaline phosphatase. The structure of the hexasaccharide component has been determined by isolation and NMR spectroscopic analysis of its dephosphorylated derivative. Additionally, the structure of a second, previously undetected tetrasaccharide component (a hexosamine) has been determined by isolation and NMR spectroscopic analysis of the acetate of its dephosphorylated derivative. It is demonstrated that CE is an ideal method for the quality control of the oligosaccharide phosphate fraction for use in the production of PI-88.

Analysis of saccharides in beer samples by flow injection with electrospray mass spectrometry

Saccharides in foods play important roles, as they are essential substrates for fermentation processes. In brewing, the concentration of maltooligosaccharides influences the characteristics of beers and therefore their determination is of great practical interest. Electrospray ionization mass spectrometry (ESI-MS) was applied to identify and characterise maltooligosaccharides in beer samples. The effects due to different cation concentrations and dilution of samples were studied. Furthermore, quantitative analyses of maltooligosaccharides by means of flow-injection ESI-MS (FI/ESI-MS) of 1-microL beer samples (diluted 1000-fold) are described.

Sub-ambient temperature effects on the separation of monosaccharides by high-performance anion-exchange chromatography with pulse amperometric detection. Application to marine chemistry

The effects of column temperature in the range 10-45 degrees C using high-performance anion-exchange chromatography (HPAEC) and pulse amperometric detection are described for the determination of monosaccharides. The influence of temperature was tested with an isocratic elution of NaOH at concentrations varying from 2.5 to 20 mM and with a post-column addition of 1 M NaOH. The results showed that small changes of temperature greatly affect retention times and resolution (Rs) of monosaccharides and particularly those of the both pairs xylose-mannose and rhamnose-arabinose which cannot be simultaneously detected at usual room temperature (approximately 25 degrees C). Our results suggest that a subambient temperature of 17 degrees C and an eluent concentration of 19 mM are the more appropriate conditions for an acceptable separation (R(s rha/ara) = 1.02, R(s man/xyl) = 0.70) in a short analytical run time (35 min). The results showed that within the range of temperatures studied, enthalpy and entropy are invariant of temperature indicating that changes in the retention processes are mainly due to temperature than other associated changes in the system. This study demonstrated the importance of controlling temperature during HPAEC of monosaccharides, both to accomplish highly reproducible retention times and to achieve optimal separation of sugars. This method gave acceptable results for detection of marine sugars.

Determination of saccharides in fruit juices by capillary electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A fast method for the detection of cheap sweeteners is presented. Detecting the adulteration of foods rich in carbohydrates is complicated by the presence of variety of commercial sweeteners that are designed to match exactly the major carbohydrate profiles of these foods. Electrophoretic and mass spectrometric assays for the determination of fruit juice authenticity were developed. Capillary zone electrophoresis with indirect detection was employed to detect adulteration of juices demonstrated by the ratio of the concentrations of major low molecular mass saccharides (glucose, fructose and sucrose). Traces of oligosaccharides, which are not present in the sugar profiles of citrus fruits but are present in inexpensive sweeteners, were evaluated as the other group of target compounds. The fast determination of oligomeric starch hydrolysates in a complex matrix was tested by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and applied to orange juice. MALDI-TOFMS was shown to be a suitable method for the identification of adulteration of fruit juices by starch hydrolysates. The effects of the presence of salts and low molecular mass saccharides on the detection of oligosaccharides by MALDI-TOFMS were studied. Low molecular mass saccharides and organic acids decrease the detectability of oligosaccharides by MALDI-TOFMS, but the concentration of maltooligosaccharides present in juices sweetened with starch hydrolysates is high enough to be detected with good sensitivity.

Role of chromatography in the analysis of sugars, carboxylic acids and amino acids in food

An overview is presented of chromatographic methods currently in use to determine sugars, carboxylic acids and amino acids in foods: high-performance liquid chromatography, gas chromatography and capillary electrophoresis. As a basis of selection the following approaches can be distinguished: quantitation of constituents of several food matrices, without derivatization and in the form of different derivatives, in the presence of the matrix, or subsequently to various work-up procedures.

Analysis of natural food pigments by capillary electrophoresis

Lac, cochineal, safflower, gardenia, Monascus and elderberry pigments are used as food color additives in Japan. These natural pigments can be analyzed by capillary electrophoresis (CE). CE has several advantages over thin layer chromatography, gas chromatography and high-performance liquid chromatography, such as low capillary cost, reduced operating costs, small sample amounts, low production of waste materials and short analysis time. CE is shown to be a useful technique for the analysis of these natural food pigments and the pigments extracted from commercial food samples by solid-phase extraction method.

Electrophoretic methods in the analysis of beverages

A review of the applications of electrophoresis to the determination of various compounds in beverage samples, namely beer, hard drinks, juice, milk, soft drinks, tea and wine, is presented.

Analysis of glycosaminoglycan monosaccharides by capillary electrophoresis using indirect laser-induced fluorescence detection

Two methods for monosaccharide analysis by capillary electrophoresis (CE) using counterelectroosmotic and coelectroosmotic modes with indirect laser-induced fluorescence detection were optimised and compared. A mixture of seven glycosaminoglycan-derived hexoses was separated in alkaline fluorescein-based electrolytes and detected in both counterelectroosmotic and coelectroosmotic conditions. The fluorescein concentration and pH of the background electrolyte, and the influence of the reversal of electroosmotic flow by addition of hexadimethrine bromide on the separation were studied. Coelectroosmotic CE conditions provided better resolution and limits of detection. A 10(-6) M fluorescein solution at pH 12.25 containing 0.0005% (w/v) hexadimethrine bromide was used as background electrolyte. Quality parameters such as run-to-run, day-to-day precision and limits of detection were calculated, and better figures of merit were obtained for the coelectrooosmotic conditions than for the counterelectroosmotic mode. The coelectroosmotic method was applied to the quantitation of the hexosamine contents in glycosaminoglycans after acid hydrolysis. The method proved to be suitable for the determination of dermatan sulfate in heparin down to 2% (w/w).

State-of-the-art of capillary electrophoresis with application to the area of glycoconjugates

Glycoconjugates constitute a major group of biomolecules, which participate in several biological functions and processes. Their carbohydrate components play key roles in determining the properties of glycoconjugates and, therefore, analysis and structural characterization of carbohydrates are essential. Capillary electrophoresis, due to its high resolving power and sensitivity, has been successfully used for the analysis of carbohydrates. In this review the principles of high-performance capillary electrophoresis; mechanisms employed for glycoconjugate analysis as well as the various detection techniques used are summarized.

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.

Simultaneous determination of monosaccharides in glycoproteins by capillary electrophoresis

A rapid, easy, and reproducible capillary electrophoretic method for the simultaneous determination of acidic, neutral, and amino sugars and sugar alcohols was developed. Underivatized mannuronic acid, glucuronic acid, galacturonic acid, N-glycolylneuraminic acid, N-acetylneuraminic acid, glucosamine, galactosamine, mannose, xylose, glucose, galactose, fucose, ribose, mannitol, sorbitol, xylitol, and inositol were simultaneously determined with indirect UV detection using 2,6-pyridinedicarboxylic acid as a background electrolyte. A highly alkaline pH condition was used in order to charge carbohydrates negatively and to promote migration toward the anode. Electroosmotic flow was reversed to the direction of the anode by adding cetyltrimethylammonium bromide to the electrolyte. The separation of the carbohydrates was investigated by optimizing the operating pH value and satisfactory resolution was obtained at pH 12.1. The relative standard deviations of the method for carbohydrates were between 0.02 and 0.33% for migration times and were greater than 2.7% for peak areas (n = 6). The minimum detectable level ranged from 23 to 71 microM with a 6-nl injection at a signal-to-noise ratio of 3. This method was applied to the composition analysis of monosaccharides in glycoprotein. After acid hydrolysis of fetuin under each optimum condition, sialo, neutral, and amino sugars were quantified under the same electrophoretic condition.

Capillary zone electrophoresis of bile acids with indirect photometric detection

Investigations in our laboratory have demonstrated that capillary zone electrophoresis (CZE) with indirect photometric detection is a viable approach to the separation and identification of free bile acids along with their taurine and glycine derivatives. Various parameters such as pH, organic solvent concentrations, column temperature, and type of chromophore electrolyte were investigated to optimize the electrophoretic separation and to maximize the peak capacity. The quality of separation of bile acids can be dramatically improved by incorporating gamma-cyclodextrin (gamma-CD) in the running electrolyte. This improvement in resolution is accompanied by a decreased migration time, suggestive of an increase in association of gamma-CD with bile acids. As a result, a CZE separation of all 15 bile acids was possible in approximately 30 min using 5 mM adenosine 5'-monophosphate, 7 mM gamma-CD in 75% (v/v) methanol at pH 7.0.

Detection of underivatized carbohydrates in capillary electrophoresis with a bienzyme electrode

A new approach to detect underivatized carbohydrates in capillary zone electrophoresis (CZE) with a bienzyme electrode is described. The bienzyme electrode is based on immobilization of two enzymes, glucose oxidase and amyloglucosidase, on a platinum microelectrode. Maltose and glucose were used as substrates to establish the method and study its feasibility. Using this electrode, underivatized glucose and maltose were determined after separation in 60 mM borate buffer (pH 9.3) by CZE. A liquid junction, between the surface of the bienzyme electrode and the outlet of the separation capillary, was used to lower the pH of the eluting separation borate buffer so that the immobilized enzymes could maintain high activities. The detection limits were 0.17 mM for maltose and 0.35 mM for glucose. The effects of borate ion and pH on the responses of the bienzyme electrode to maltose and glucose are discussed. The bienzyme electrode did not show any decay in responses to maltose or glucose during one week of continuous operation.

Separation of disaccharides as their borate complexes by capillary electrophoresis with indirect detection in visible range

Borate complexation was used to make possible the separation of disaccharides by capillary electrophoresis with indirect detection. A high borate concentration did not affect the indirect detection sensitivity in as negative a way as predicted previously. The concentration sensitivity for sucrose was determined to be 2 mM at the borate concentration of 200 mM in running electrolyte. The newly introduced background [corrected] chromophore, p-nitrophenol, allows the monitoring of the separation process in a visible range at 400 nm. This also enables the indirect detection of UV-absorbing compounds in complex mixtures in which they would be impossible to detect with a UV-absorbing background [corrected] chromophore.