Measurement of Reducing Sugar in Black Liquor by Dual Wavelength Spectrophotometry

Abstract

The lignin will drag interference in the system of the sugar determination. Dual wavelength spectrophotometry can remove the interference when making use of the DNS to detect the reducing sugar content in the black liquor. After the analysis to the absorbency graphs of the lignin and the glucose dissolved in the DNS solution at specific wave length region in the ultraviolet-visible light, and the contrast between the coefficients of the relation curves between their absorbency and their concentration at specific wave length, the test wave length is intended to be 520 and 570nm. From the relation curves between the absorbency of the lignin and its concentration at 520nm and 570nm, the magnification coefficient of the differential signal were defined as K2=5.338, K1=3.288.The correction index k=1.2. Then the concentration c (g/L) of the glucose solution can be figured out through formula c=(S/k-0.0165)×M/0.821.Then a group of glucose solution with same glucose addition but different lignin addition had been measured. So this method is effective to detect the reducing sugar content in the black liquor.