Determination of Brett character responsible compounds in wines by using multiple headspace solid-phase microextraction

This study presents a method based on the use of multiple headspace solid-phase microextraction (MHS-SPME) for the quantitative analysis of 4-ethylphenol, 4-ethylguaiacol, 4-vinylphenol and 4-vinylguaiacol. MHS-SPME is a modification of SPME that implies several consecutive extractions from the same sample and avoids possible matrix effects. This study demonstrates the existence of a matrix effect in the analysis of compounds responsible for Brett character in wine when an HS-SPME based method is used with a carbowax/divinylbenzene (CW/DVB) fibre. For this reason, MHS-SPME is proposed as an alternative technique with respect to HS-SPME. The method proposed was validated and the detection limits obtained were 0.06 μg/l for 4-ethylguaiacol and 4-ethylphenol and, 0.20 μg/l for 4-vinylguaiacol and 0.12 μg/l for 4-vinylphenol. These detection limits are below the odour detection thresholds of the compounds in wine matrices. The repeatability obtained, in terms of relative standard deviation (RSD), was considered acceptable, ranging from 1 to 12%. To evaluate the applicability of the proposed MHS-SPME method, concentration results were compared with those obtained with the standard addition method, and the results were similar with both methods. Furthermore, the new method was satisfactorily applied to a number of commercial red, white and rosé wines. Therefore, MHS-SPME can be considered as an alternative to avoid the matrix effect in wine samples.