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

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Abstract
Sample stability, extraction procedures and solvents and various gas chromatog- raphic procedures were studied in an attempt to improve procedures for the determination of lignin by the nitro- benzene 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 ma- terial. 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 azoxy- benzene 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.