Determination of reducing ends with flow injection analysis with amperometric detection: application to enzyme-hydrolysed methyl cellulose

A novel method for detection of reducing ends of sugars is proposed, based on the use of Fe(CN)(6)(3-) as the oxidant in combination with amperometric detection and flow injection analysis (FIA). The method is very sensitive, giving values of < 10 mu M for the limit of detection for a series of mono- and oligosaccharides. Samples can be analysed every 30 s, and injection can be made fully automated, making it possible to perform on-line analysis of polysaccharide samples subjected to hydrolysis. Three methylcelluloses (MC) of different qualities were hydrolysed with three different glucanases, and the concentrations of reducing ends prior to, during and after hydrolysis were determined. Differences were observed between the results obtained using different combinations of enzymes and MCs, which revealed different selectivities of the various enzymes for the different substrates. One MC was also hydrolysed and analysed in real-time for three hours. The method proposed is superior to many of the standard methods used today, which require manual labour and have a lower sensitivity.