Microwave-accelerated derivatization processes for the determination of phenolic acids by gas chromatography-mass spectrometry

A rapid method for the derivatization of phenolic antioxidants using microw ave irradiation has been developed. Six antioxidatively active phenolic com ponents of wines and fruits, namely gallic acid, gentisic acid, vanillic ac id, caffeic acid, ferulic acid and p-coumaric acid were used in the model s tudy. The solution of phenolic acids was evaporated to dryness on a rotary evaporator followed by further drying under microwave irradiation (600 W, 3 0 s). The resultant residue was dissolved in pyridene and treated with bis( trimethylsilyl)acetamide while irradiated by microwave using high power for 30 s. Controlled reaction was carried out employing bis(trimethylsilyl)tri fluoroacetamide under conventional heating for 30 min. The trimethylsilyl d erivatives were identified and quantified on a gas chromatography/mass sele ctive detector. The mass spectral fragmentation patterns of the derivatives obtained by microwave irradiation were identical to those prepared by heat ing. The yields of microwave-assisted silylation were comparable to those f rom conventional heating. The rsd were less than 8% for six replicates. The linearity in wine matrix was nearly perfect. This method is a useful proto col to examine the phenolic constituents in wines and agricultural products . (C) 2001 Elsevier Science B.V. All rights reserved.