Carbohydrates detection systems

Yamauchi, S., Nakai, C., Nimura, N., Kinoshita, T., and Hanai, T., Development of a highly sensitive fluorescence reaction detection system for liquid chromatographic analysis of reducing carbohydrates, Analyst, 118, 773,1993. 

Torimura etal. [194] developed an analytical approach capable of determining subnanomolar amounts of carbohydrates based on the indirect detection of iodate, 103 , at a glassy carbon electrode. The method was applied as a postcolumn detection system for HPLC separation. 

This detection system is coupled with anion-exchange chromatography (48,49), which has the same alkaline pH requirements. The sensitivity of PAD is considerably higher than that yielded using the refractometric detector, with detection limit being of the order of 10 pmol (29). On the other hand, its response also depends heavily on the nature of the carbohydrate. Finally, other alternatives described in the literature include the use of nickel-based or copper-based electrodes and catalytic oxidation (50). 

In glycoprotein detection systems the carbohydrate portions of proteins are oxidized with sodium metaperiodate to generate aldehydes that can react with hydrazides. A biotin hydrazide is used to attach biotin onto the oxidized carbohydrates and horseradish peroxidase-conjugated streptavidin is used for chemiluminescence-based detection (Glycoprotein Detection Module, Amersham Biosciences, Uppsala, Sweden). 

For indirect fluorescence detection coumarin or fluorescein are used. This indirect UV (or fluorescence) detection of the separated carbohydrates appears simple, but it has some drawbacks such as the instability of the detection system itself resulting in a drift of the baseline, the unfavorable relation between the analyte and the co-ion giving low efficiencies at higher sample concentrations of the sample, and the lack of specificity for the detection. Nevertheless, this method was applied for the... 

Direct UV detection is the most versatile detection method in CE and is implemented in every commercial CE system. Unfortunately, its use for carbohydrates detection is restricted because of their lack of conjugated p-electron systems and, consequently, the relatively low... 

---