Detection Techniques for Mono-, Di-, and Oligosaccharides Analyzed with Capillary Electrophoresis

Accurate and sensitive analysis of mono-, di-, and oligosaccharides is desired in several different scientific areas due to the wide appearance of saccharides. This work focuses on the detection of mono-, di-, and oligosaccharides utilizing capillary electrophoresis (CE). Saccharide analysis with CE is challenging due to the lack of UV-absorbing chromophores in the molecular structure. CE also requires that the analytes are in their charged form, which is demanding in the case of mono-, di-, and oligosaccharides due to their high pKa-values. The first part of this work presents several detection methods and procedures to succeed in saccharide analysis with CE. A selection of the scientific work published in this area is presented to highlight the different detection possibilities. Derivatization of the analytes is commonly used to transform the saccharides into UV absorbing species. Special compositions of the background electrolyte, e.g. borate buffers and copper(II) containing buffers can be exploited to form charged complexes with the saccharides, which enhance the separation. Indirect UV detection is not as sensitive as direct UV detection of saccharide derivatives, but it is fast and useful in applications where high sensitivity is not required. Electrochemical detection (pulsed amperometric detection and contactless conductivity detection) is especially useful in miniaturized and portable systems. An advantage of electrochemical detection is also that no sample pretreatment or special reagents are required. Mass spectrometry (MS) detection is a powerful tool when detailed information about oligosaccharide structures is required and when the sample amounts are small. MS detection is therefore especially suitable in biochemical applications. In the second part of this work, CE was utilized for the separation and quantification of five novel ionic liquids and the quantification of acetate and xylose in ionic liquid matrices. The internal standard method was used in the quantitative work. The novel ionic liquids were detected with direct UV detection and the limit of detection ranged from 2-5 µg/mL. Resolution and number of effective plates were calculated from the separation studies. In the quantitative work, calibration curves were obtained for four of the novel ionic liquids. CE with indirect UV detection was used for the quantification of acetate, which is a typical counter ion in ionic liquids. A calibration curve for acetate was obtained and the linearity ranged from 0.0025 to 0.2 mg/mL. The method was successfully applied to the determination of the concentration of acetate in a standard sample containing the ionic liquid [MTBDH][OAc]. In the last part of the work, solid phase extraction was utilized to extract ionic liquids from industrial samples. CE with direct and indirect detection was used to check if the extraction was complete and if saccharides were present in the extracts. A calibration curve for xylose was constructed and the linear range for xylose was 0.05 to 3 mg/mL. It was found that the developed method for xylose detection was not sensitive enough to detect possible saccharide residues in the extracts and the analytical procedure requires further development