Use of Nitrobenzene Oxidation for Study of Lignin Composition with an Improved Method for Product Extraction,

Abstract

Sample stability, extraction procedures and solvents and various gas chromatographic procedures were studied in an attempt to improve procedures for the determination of lignin by the nitrobenzene oxidation technique. Extraction of oxidation products with ether, although needed to extract p-coumaric acid, resulted in a marked decrease in sample stability and increased extraneous material. Studies using a variety of phases and sample preparations showed that with 5% OV-25 on Gas Chrom Q the peaks corresponding to caffeic and ferulic acids were largely or entirely azoxybenzene and p-phenylazophenol. The introduction of disposable diatomaceous earth columns for extracting oxidation products resulted in a faster procedure and the removal of the by-products azoxybenzene and p-phenylazophenol from the extracted products.