A multiresidue derivatization gas chromatographic assay for fifteen phenolic constituents with mass selective detection.

We have developed a GC/MS method to simultaneously measure the concentrations of 15 biologically active phenolic components of wine: vanillic acid, gentisic acid, m- and p-coumaric acid, gallic acid, ferulic acid, caffeic acid, cis- and trans-resveratrol, epicatechin, catechin, morin, quercetin, and cis- and trans-polydatin. Wine (1 mL) was diluted 1:1 with water to reduce the alcohol content and extracted on a preconditioned C-8 solid-phase extraction cartridge. The phenolic compounds were eluted with ethyl acetate, evaporated to dryness, and derivatized with bis(trimethylsilyl)trifluoroacetamide/pyridine. The TMS derivative of each phenolic compound was analyzed on a GC/MSD coupled to a DB-5HT capillary column using one target and two qualifying ions for each compound in a total run time of 26 min. Resolution and quantitation of all compounds were excellent, with linear calibration curves over a wide range. The lowest detection limit was for gentisic acid (24 µg/L) and highest for quercetin (843 µg/L). The average percent recovery and coefficient of variation (mean precision) ranged from 90.7 to 104.6 (except morin, 72.2%) and 4.0 to 10.2 (except morin, 16.1%, and quercetin, 16.0%) respectively. This method has been applied to solid vitaceous plant materials as well as wine and should be suitable to measure polyphenols in fruit, vegetables, and other foods provided that efficient extraction techniques are employed.

Method to assay the concentrations of phenolic constituents of biological interest in wines.

We describe a reversed-phase HPLC method that uses gradient elution and diode array detection to quantitate eight biologically active phenolic constitutions of wine: the cis and trans isomers of resveratrol and their glucosides, catechin, epicatechin, quercetin, and rutin. ODS Hypersil served as the stationary phase; the gradient was formed by acetic acid, methanol and water. Each analysis required an equilibration period of ten minutes and a run time of fourty minutes for completion. Satisfactory peak resolution was achieved following direct injection of a 20-muL sample, and validation was accomplished by on-line spectral comparisons with known standards. Excellent linearity was obtained for all constituents, and the detection limits ranged from 30 mug/L (trans-resveratrol) to 1.5 mg/L (catechin). Recoveries approximated 100% range (95.2-105.5%), and the method provided good precision, with coefficients of variation between 1.17 and 3.38%. All of the phenolics measured were reasonably stable in opened wines protected against sunlight for up to 1 week at room temperature or 4 degrees C, but most showed losses of 10-40% when stored for 6 weeks at either temperature.