Mixed-mode solid-phase extraction followed by dispersive liquid-liquid microextraction for the sensitive determination of ethylphenols in red wines.

Selectivity of mixed-mode solid-phase extraction (SPE) was combined with the concentration power of dispersive liquid-liquid microextraction (DLLME) to obtain a sensitive, low solvent consumption method for gas chromatography-mass spectrometry determination of ethylphenol off-flavours (4-ethylphenol, EP; 4-ethylguaicol, EG and 4-ethylcathecol, EC) in complex red wine samples. Under optimized conditions, limits of quantification (LOQs) between 0.3 and 0.8 ng mL(-1) were obtained using just 5 mL of wine and 0.06 mL of 1,1,1-trichloroethane (TCE) as extractant in the DLLME step. Analytes were acetylated after SPE and previously to DLLME concentration to enhance the performance of their GC-MS determination. The overall extraction efficiency of the method was unaffected by the particular characteristics of each wine; thus, accurate results (relative recoveries from 89 to 109% for samples spiked at concentrations from 20 to 1000 ng mL(-1)) were obtained using matrix-matched standards, without requiring the use of the time consuming standard addition quantification methodology. The applicability of the method was demonstrated with the analysis of different red wines. Analytes concentrations varied from 6 to 2265 ng mL(-1) (EP), 0.8 to 251 ng mL(-1) (EG) and non-detected to 158 ng mL(-1) (EC).