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Sorptive extraction with in-sample acetylation for gas chromatography-mass spectrometry determination of ethylphenol species in wine samples

Carpinteiro, I., Abuín, B., Rodríguez, I., Ramil, M., Cela, R.
Journal of chromatography 2010 v.1217 no.46 pp. 7208-7214
acetylation, aqueous solutions, catalysts, derivatization, ethyl acetate, gas chromatography-mass spectrometry, ionic strength, off flavors, potassium bicarbonate, red wines, silicone, sodium chloride, temperature
An inexpensive and effective sample preparation procedure for the determination of three ethylphenolic off-flavours (4-ethylphenol, 4-ethylguaiacol and 4-ethylcathecol) in wine samples is presented. Analytes were in situ acetylated and concentrated using a disposable silicone sorbent (DSS) exposed to the diluted sample. After that, the analytes were recovered with ethyl acetate and determined by gas chromatography with mass spectrometry. The influence of different parameters (volume of acetic anhydride, basic catalyst, ionic strength, sorbent format, sampling mode and extraction time) on the efficiency of derivatization and extraction steps is discussed. Under optimized conditions, 2mL of wine were diluted with 15mL of an aqueous solution of potassium bicarbonate (5%, m/v) in a 22mL vessel, containing 2g of sodium chloride. The volume of acetic anhydride and the extraction time were set at 90μL and 2h, and the extraction was carried out at room temperature (20±2°C). Analytes were concentrated using a silicone disc (5mm diameter×0.5mm thickness) and further desorbed with 0.2mL of ethyl acetate. The achieved limits of quantification (LOQs), defined as the concentration of each compound providing a signal 10 times higher than the baseline noise, stayed between 5 and 15ngmL⁻¹. The method provided a linear response range of up to 5000ngmL⁻¹ and relative recoveries from 91% to 116%. The 4-ethylphenol off-flavour was detected in most red wine samples at concentrations of up to 2700ngmL⁻¹.