Reducing sugar content in hemicellulose hydrolysate by DNS method: A revisit

DNS reducing sugar method was revisited for hemicellulose hydrolysate. A series of experimental conditions were investigated for determining reducing sugar content in hemicellulose hydrolysate, including the absorbency (ABS) wavelength, DNS reagent dosage, color reaction time, pH of the sample, stability after color reaction, reproducibility of undetermined sample's ABS value, linearity and limit of detection, recovery and interference from other chemicals. It was revealed that the optimum measurement procedure is by adding 1.5 mL DNS reagent, maintaining in boiling water bath for 5 min, cooling down to room temperature before determining the sample's ABS value in 10 min. The calibration equation is found to be C=4.24 × ABS+0.39, for reducing sugar. Here C is reducing sugar concentration in mM and the limit of detection is at 0.5 mM. Interference experiments showed that acetate has no apparent inhibitory effect on the color reaction. The accuracy of the DNS method is estimated at 10%. A summary of the method is presented at the end.