Gas chromatographic determination of diethylene glycol in wine, grape juice and grape-juice concentrates

A gas chromatographic method for the quantitative determination of diethylene glycol in wine, red and white grape juice, and red and white grape juice concentrates is described. The method includes continuous extraction of the diethylene glycol with ethyl acetate by the aid of a rotation perforator. Using the new generation of chemically bonded stationary phases on fused silica together with an appropriate modern cold on-column injection system coupled with an autoanalyzer and a retention gap, the GLC analysis is shown to provide adequate information for quality control purposes. Linearity, precision and recovery with the described procedure were investigated. The precision of the method was studied using a sample containing approximately 65 mg/l diethylene glycol. Twelve separate determinations were performed by the described method; the coefficient of variation was 3.9%. The detection limit of our method is 5 mg/l diethylene glycol both for wine, grape juice and grape juice concentrates. Recovery data are based on wine, grape juice and grape juice concentrates fortified with diethylene glycol at different levels. The ranges of concentration used in this study were 10 mg/l to 10 g/l for wine and 10 mg/l to 100 mg/l for grape juice and grape juice concentrate. The average recovery of diethylene glycol for wine at all concentrations tested was 98.8%; coefficients of variation were between 1.6 and 8.0%. Recoveries of diethylene glycol added to grape juice at the level of 10 mg/l to 100 mg/l were 96% to 109%.