Solvent-free method for the determination of lignin-derived phenols in sediments

A solvent-free method that uses headspace solid-phase microextraction and gas chromatography with flame ionization detection is proposed for the determination of lignin-derived phenols in sediments. The extraction and derivatization conditions for the simultaneous analysis of acetosyringone, acetovanillone, syringaldehyde, vanillin, ferulic acid, syringic acid, vanillic acid, p-hydroxybenzoic acid, and p-coumaric acid were optimized using a central composite design. After optimization, the best results were obtained with the following conditions: exposure of the polyacrylate fiber to the headspace with 60 μL of N,O-bis(trimethylsilyl)trifluoroacetamide as a derivatizing agent for 15 min and then extraction in the headspace of 100 mg of sediment (previously spiked with lignin-derived phenols) for 35 min. The accuracy of the method was estimated based on recovery tests at two concentration levels and by comparison with a high-performance liquid chromatography method reported in the literature. Based on the t-test with a confidence level of 95%, no statistical differences were observed. The detection and quantification limits for the target compounds varied according to their characteristics: values at the microgram per gram level for nonacid compounds and milligram per gram level for phenolic acids, due to the lower volatility of the derivatives.