Determination of five 3-alkyl-2-methoxypyrazines employing HS-SPME-GC-NPD: Application in evaluation of off-flavor of South American wines

Abstract

High concentrations of 3-alkyl-2-methoxypyrazines (MPs) in wines can affect the quality and contribute to the rejection of consumers. This work proposes the determination of five MPs in nine wine samples from South America using headspace solid phase microextraction with gas chromatography coupled to nitrogen-phosphorus detector. The separation of the analytes was performed with a HP 5 capillary column in temperature gradient mode and injection in splitless mode. The optimization of the main parameters gives the optimal extraction conditions: Divinylbenzene-Carboxen-Polydimethylsiloxane fiber, sample dilution ratio of 1:3 with water, salt addition of 30 % (w/v) sodium chloride, extraction time of 30 min and extraction temperature of 35 °C. The main parameters of merit of the method were evaluated, showing coefficients of determination greater than 0.995, limits of detection ranging from 6.10–31.2 ng L−1, recovery from 75.2–118% and precisions with values less than 20 %. The validation parameters obtained and the concentration levels of ng L−1 achieved characterize this method as efficient for the determination of these off-flavors in wine. From the nine analysed wines, 3-ethyl-2-methoxypyrazine and 3-isobutyl-2-methoxypyrazine were identified and quantified. The levels are well above the odor detection threshold, thus contributing to generation of off-flavor in the aroma and flavor of these wines.