Determination of ethylphenol compounds in wine by headspace solid-phase microextraction in conjunction with gas chromatography and flame ionization detection
Résumé
Headspace solid phase microextraction (HS-SPME) was investigated as a solvent-free alternative method for the extraction and determination of 4-ethylphenol (EP) and 4-ethylguaiacol (EG) in red wine by capillary gas chromatography with flame ionization detection (FID) and compared to liquid–liquid extraction. For HS-SPME, better results were obtained with saturated sodium chloride samples, at 55°C, using a 85μm polyacrylate fiber. An absorption time of 40min was needed to reach the absorption equilibrium for EG. This 40-min duration corresponds to the beginning of EP equilibrium and was selected for the experiments. In these conditions, the calibration graphs were linear in the range 5–5000μgl−1 and the sensitivity was nearly the same for the two compounds. The detection limits were in the low μgl−1 range. In model wine solutions, result obtained with the liquid–liquid extraction method exhibit a linear calibration between 25 and 10,000μgl−1 with a detection limit of 1μgl−1, but, the relative standard deviations of the EP and EG result in the low concentration range (<50μgl−1) are higher than those obtained by HS-SPME (15% compared to 2% for EP and 12% compared to 5% for EG). Taking into account the numerous volatile compounds in wine, HS-SPME is a rapid and valid alternative technique for use in the determination of ethylphenols at trace levels.
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