Application Of Headspace Gas Chromatography In The Determination Of Functional Groups Of Several Biomass-based Materials

Bio-based materials are clean,renewable and biodegradable,making them an excellent alternative to petroleum-based materials.A biomass-based material typified by wood,bamboo,cellulose,hemicellulose,lignin,chitosan,starch,and derivatives,containing a considerable amount of reactive groups(carboxyl,hydroxy,amino,acetyl,etc.).The content of these groups not only affects the structure and properties of the material itself,but also determines its potential for further modification to prepare new functional materials.Therefore,the establishment of a detection method suitable for functional groups of biomass-based materials is of great significance for the better development and utilization of biomass energy.In this paper,nanocellulose,carboxymethylcellulose,chitosan and bamboo were selected as the research objects,and the suitable pretreatment method was selected.The method of determining the content of carboxyl,amino and acetyl groups was established based on headspace gas chromatography.A headspace gas chromatography method for the determination of the carboxyl group content of nanocellulose was established.The nanocellulose suspension was pretreated by ion exchange resin instead of the traditional acidification method,which avoided the gelation of nanocellulose and successfully–COONa is converted to the form of–COOH in the nanocellulose.Then the content of–COOH was calculated by headspace gas chromatography to detect the CO~2 content of the reaction between sodium bicarbonate solution and-COOH.The results show that the relative standard deviation(RSD)of the method is less than 3.7%,the quantitative detection limit is 0.1mmol/g,and the relative deviation between the conductivity and the titration method is within 15%.The sensitivity is high and the result is reliable.A headspace gas chromatography method for determining the degree of substitution of carboxymethyl cellulose was established:CMC-Na was converted to CMC-H form by strong acid cation exchange resin,and then the sodium bicarbonate solution reacts with the carboxylic acid group of CMC-H to form carbon dioxide,which detected by headspace gas chromatography to calculate the degree of substitution of sodium carboxymethylcellulose.The results show that the detection accuracy of this method is high(RSD<4%).Compared with the traditional method,the relative error of the detection result is less than 7%.It has the advantages of simple operation,high efficiency and high accuracy.Providing a fast and reliable method for the detection of degree of substitution of sodium carboxymethyl cellulose..A headspace gas chromatography method for the determination of chitosan acetyl groups was established:chitosan can be swelled in sodium bicarbonate solution,and its amino group is alkaline to inhibit the degradation of sodium bicarbonate,and then the different degree of deacetylation of chitosan is determined.For the degree of deacetylation,the method can quickly evaluate chitosan.A headspace gas chromatography method for the determination of the acetyl content of biomass-based materials was established:The bamboo and hydrolyzate after hydrothermal pretreatment were used as research objects,and oxalic acid pretreatment was carried out in order to convert the acetyl group in the sample into acetic acid.Then the content of acetic acid is tested to obtain the content of acetyl groups in the sample.The results show that the method has good measurement accuracy(relative standard deviation of liquid sample is less than2.09%,relative standard deviation of solid sample is less than 2.83%)and accuracy(recovery of acetyl quantitative determination is 96.2-104%).For biomass liquid samples,the limit of quantitation for this method is 163mg/L,and for biomass solid samples,the limit of quantitation is 0.11%.