Optimization of ultrasound assisted-emulsification-dispersive liquid–liquid microextraction by experimental design methodologies for the determination of sulfur compounds in wines by gas chromatography–mass spectrometry

VIVIANA P. JOFRÉ; MARIELA V. ASSOF; MARTÍN L. FANZONE; HÉCTOR C. GOICOECHEA; LUIS D. MARTÍNEZ; MARÍA F. SILVA

ANALYTICA CHIMICA ACTA

ELSEVIER SCIENCE BV

Año: 2010 p. 126 - 135

0003-2670

A new method was developed for analyzing sulfur compounds in the aroma of white winesusing ultrasound assisted-emulsification-dispersive liquid–liquid microextraction coupled with gaschromatography–mass spectrometry detection. In the present work, the analytical method for simultaneousdetermination of seven sulfur compounds (methylmercaptoacetate, methyl(methylthio)acetate, 2-methylthioethanol, 3-methylthiopropanol, 3-methylthiohexanol, 4-methylthio-4-methyl-2-pentanoneand hexanethiol) is reported. Parameters that affect the efficiency of the methodology such as extractingand dispersing solvents, sample volume, ion strength, cavitation time and centrifugation time wereinvestigated using a fractionated factorial 26–1 (R =V) screening design. Then, the factors presenting significantpositive effects on the analytical response (extracting volume, ion strength, cavitation time andcentrifugation time) were considered in a further central composite design to optimize the operationalconditions for the ultrasound assisted-emulsification-dispersive liquid–liquid microextraction procedure.Additionally, multiple response simultaneous optimization by using the desirability function wasused to find the optimum experimental conditions. The best results were obtained using pH sample4.25, extractant volume 150L, ionic strength 8.75% NaCl, cavitation time 20 s and centrifugation time50 s. The use of the optimized ultrasound assisted-emulsification-dispersive liquid–liquid microextractiontechnique allowed to obtain the best extraction results with the minimum interference from othersubstances from the matrix, and it allowed to quantify the analytes in white wine samples by calibrationgraphs. Recoveries ranging from 91.99% to 125.87% for all sulfur compounds proved the accuracy of theproposed method in white wine samples. Method detection limits were in the range of 0.36–1.67 ngmL−1and limits of quantitation were between 0.63 and 3.02 ngmL−1 for sulfur compounds in white wine samples.The proposed methodology was successfully applied for the determination concentrations of sulfurcompounds in different commercial Chardonnay wine samples from Mendoza, Argentine.