Development of Method to Determine the Concentration of Alkali-Soluble Lignin using Coomassie Brilliant Blue G-250

Abstract

A new method involving the non-covalent binding of Coomassie Brilliant Blue G-250 (CBBG) to alkali-soluble lignin was developed. The binding of the dye to alkali-soluble lignin caused an increase in visible absorption at the maximum wavelength of 630 nm or 640 nm. A linear correlation of the absorbance at their maximum absorbing peak with alkali-soluble lignin concentration was observed. Lignin estimation in black liquor showed that the result of the new method and the gravimetric methods after acidification were closer to quantitative information than that obtained from UV spectroscopy. The isothermal titration calorimetric experiments, and Fourier Transform Infrared (FTIR) spectroscopy comparative analysis of precipitates washed by water, 4% ethanol, and 95% ethanol indicated that CBBG was bound to alkali-soluble lignin, and the binding was noncovalent. This potential method is reproducible, rapid, and cheap, and there is little or no inference from carbohydrate degradation products.

Determination of lignin concentration in bleaching effluent via Coomassie brilliant blue G-250 method

“…3). This indicated that the increase in absorbance at 640 nm in the newly prepared mixtures of alkali lignin solution and CBBG was from a combination of CBBG and lignin; which was consistent with non-covalent combination between the lignins and the CBBG to increase the absorption at 640 nm as shown in previous research (Wang et al 2016).…”

“…However, their CBBG mixture absorbance at 460 nm changed less than 5%, when compared to the control mixture absorbance at 460 nm. This indicated that the lignin concentrations in the four kinds of bleaching effluents possibly can be determined via the CBBG method, similar to pulping black liquor (Wang et al 2016).…”

“…The Coomassie Brilliant Blue G-250 reagent (CBBG reagent) was prepared as previously reported by the author (Wang et al 2016).…”

“…The preparation of the standard curves for each lignin solution and the determination of the lignin content in the corresponding bleaching effluents were performed according to the previous report of the authors (Wang et al 2016).…”

“…The Coomassie Brilliant Blue G-250 (CBBG) method is suitable for determining the lignin content in aspen kraft pulping black liquor and it is rapid, cheap, and free from interference of carbohydrate degradation products and phenolic compounds (Wang et al 2016). However, the applicability of the method to determine the lignin content in bleaching effluent was unclear.…”