Chemical characterization of ozonated lignin solutions from corn (Zea mays) stalk and poplar (Populus deltoides) wood by capillary gas chromatography

Corn (Zea mays) stalk and poplar (Populus deltoides) wood lignin was converted into monomeric aromatic compounds and short chain aliphatic carboxylic acids. The main reaction products were separated and identified using capillary gas chromatography-mass spectrometry on an HP-5 column. The compounds were considered as positively identified when their mass spectra and GC retention times agreed with those of authentic standard samples. The quantitative estimation of the identified reaction products was accomplished on an OV-101 capillary column by gas chromatography-FID using the internal standard method. Among the aromatic compounds, aldehydes (p-hydroxybenzaldehyde, vanillin, and syringaldehyde), acids (p-hydroxybenzoic, vanillic, 3,4-dihydroxybenzoic, and syringic), and one phenol (hydroquinone) were determined. In addition, the aliphatic carboxylic acids: glycolic, oxalic, malonic, glyoxylic, butanedioic, glyceric, and malic acid were identified. All the calibration curves of the quantified compounds approximated to a straight line. For both corn stalk and poplar wood lignins, the major components were the aromatic aldehydes (71 and 64% of the characterized fraction, respectively), followed by the aliphatic carboxylic acids (20 and 21% of the characterized fraction, respectively).