Fatty acid and solidification floating organic drop-based dispersive liquid-liquid microextraction method coupled with high performance liquid chromatography for the determination of 4-ethylphenol and 4-ethylguaiacol in wines

A method of fatty acid and solidification floating organic drop-based dispersive liquid-liquid microextraction (FA-DLLME-SFO) coupled with high performance liquid chromatography to determine 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG) in wine samples was developed. The method required less than 4 min to extract the two target analytes from wine samples, and only three kinds of eco-friendly solvents including fatty acid, ammonium hydroxide and sulfuric acid were used. The analytical parameters affecting the extraction efficiency including the volumes of the sample, the nature and volumes of the extraction solvent, the volumes of ammonium hydroxide and sulfuric acid, and the amount of salt addition were optimized. Under the optimum conditions (10 mL sample, 100 mu L octanoic acid, 110 mu L 25%-28% (mass percentage) NH4OH, 0.8 mL 98% (mass percentage) H2SO4, 3.0 g NaCl), the linear ranges were 0.02-1.0 mg/L with correlation coefficients of 0.9997 and 0.9999 for 4-ethylphenol and 4-ethylguaiacol, and the relative standard deviations (RSDs) were 6.2% and 3.5%, respectively. The LODs were 6.33 mu g/L and 5.81 mu g/L, and the enrichment factors (EFs) were 79 and 86 for 4-ethylphenol and 4-ethylguaiacol, respectively. The present method was applied to the determination of the two analytes in white wine and beer samples, and the recoveries of them were in the range of 81.4%-108.7% with the RSDs less than 8.9%. The method is simple and eco-friendly for rapid analysis of 4-ethylphenol and 4-ethylguaiacol in wine samples.