Separation And Characterization Of Lignin Degradation Products

Lignin is second only to cellulose in biomass resources and the most abundant naturalaromatic polymer. It has a prosperous prospect to prepare bio-fuel and fine chemicals byusing lignin, in which of the key is to degrade lignin macromolecules. However, lignindegradation products are very complex, so it has been of significance to study directionaldegradation of lignin, separation and characterization of degradation products. Using gelchromatography can separate lignin degradation products into different fractions accordingto their sizes of molecules. The characterization of lignin degradation products is useful toexplore the degradation mechanism and the comprehensive utilization of degradationproducts.A method for the determination of monophenolic compounds derived from oxidativedegradation of lignin was developed by combination of ultra performance liquidchromatography with high resolution mass spectrometry. The efficient separation of ninemonophenolic compounds was carried out on a RP C18column with the mobile phase of0.1%(V/V) formic acid aquous-10%(V/V) methnol/acetonitrile at30℃at a flow rate of0.2ml/min, and the detection wavelength is280nm. Electrospray ionization coupled with highresolution time of flight mass spectrometry under positive ionization mode was used for thequalitative identification of monophenolic compounds degraded from lignin. Thequantitative analysis was performed with external standard method based on high resolutionextracted ion chromatography. The linear ranges were5.0-1000.0μg/L with correlation ofmore than0.9998. The LODs and LOQs were0.1~0.3μg/L and0.3~0.5μg/L,respectively．The average recoveries were98.87.1%-105.11%with less than relativestandard deviations of1.7%．The method is rapid，sensitive and easy to operate.Sephadex G-10was used to separate lignin degradation products. The effects of pH,composition of the mobile phase on the separation efficiency were investigated.Experimental results show that alkali lignin degradation products were separated with10%ethanol (V/V) of NaOH aqueous solution at pH of10.5as the mobile phase at room temperature. The purity of monophenolic degradation products separated can reach morethan95%. The monophenolic degradation products are further purified usingreversed-phase C18packing the chromatographic column. The9monophenolic lignindegradation products were characterized using NMR to support the evidence to indentifymonophenolic degradation products. This study can provide a reference for preparingadvanced liquid fuel and high value chemicals using degradation products of alkali lignin asraw materials.