Development of a rapid headspace gas chromatographic method for determination of acetic acid in biomass hydrolysate

During the autohydrolysis pretreatment, the acetic acid is generated by the cleavage of acetyl groups in the hemicelluloses. The acetic acid plays a crucial role in the extraction of hemicelluloses, the degradation of cellulose and the dissolution of lignin. In this study, a headspace gas chromatography (HS-GC) method is developed for quantitative determination of acetic acid in biomass hydrolysate. The method is based on the “in-vial” derivatization reaction of alcohols and acids, in which the acetic acid is converted to corresponding esters in the HS thermostat (instead of the outside water bath). The generated esters are then determined directly by the GC coupled with FID. Compared with the other six different kinds of derivatization regents, the NaHSO₄/ethanol has obtained better sensitive and was selected as the preferred derivatization regent. The present method has an excellent reproducibility (RSD <0.69%), a satisfactory linearity (R² > 0.9991) and a demonstrated recovery (97.1%~103.1%). The limits of the quantification (LOQ) and detection (LOD) were 2.38 and 0.78 mg/L, respectively. Furthermore, cross-validation with the commonly used HPLC method demonstrated that the present HS-GC method has a lower LOQ and an advantage of only 8 min requirement for GC analysis. The method is rapid, sensitive and suitable for measuring acetic acid in the multifarious biomass hydrolysates in pulping and biorefinery industries.