MONITORING OF REDUCING SUGARS BY FLOW-INJECTION ANALYSIS USING P-HYDROXYBENZOIC ACID HYDRAZIDE

In this work, p-hydroxybenzoic acid hydrazide has been used as a reagent to determine reducing sugars using flow-injection analysis with photometric detection (410 nm). Parameters such as the temperature, alkalinity, reactor length, injection volume, flows and reagent concentration were examined for their optimum conditions. Systems catalysed by bismuth for low analyte concentrations and non-catalysed for higher levels, containing only a single sugar (sampling frequency 60-80 h-1) and a system with a longer residence time (sampling frequency 30 h-1) in which the different responses of various sugars can be minimised, are described. Samples (fruits and beverages) measured with the latter system in the calibration range 0.08-0.6 g/l gave a typical R.S.D. of 2%.