MULTIELEMENT STABLE-ISOTOPE RATIO ANALYSIS OF GLYCEROL TO DETERMINE ITS ORIGIN IN WINE

The adulteration of wine with glycerol is considered to be a problem i n European wine-producing countries. The latest control methods are ma inly based on the detection of impurities from commercial products, bu t suffer from the raising efficiency of the purification processes. As there is little chance of being able to identify glycerol from differ ent sources on the basis of a method which uses only one isotope, a mu ltielement approach was tested. Glycerol from wine showed the lowest r elative enrichment with D, mainly in position C-2, a relatively high O -18 content, and very negative delta(13)C values, which significantly correlated with those of ethanol from the same wines. The isotopic dat a of glycerol samples from different sources were in agreement with th ese given by indices of origin (impurities). These data allowed us to identify the origin of these glycerol samples, i.e. whether they were produced industrially or synthesised by animals or plants. Glycerol of plant origin was most similar to glycerol found in wine. The combinat ion of several isotopic data by discriminance analysis yielded cluster s of data obtained from glycerol samples of similar origin. Taking int o account the characteristics of possible mixtures, proof that wine ha s been adulterated depends on the origin and isotope levels of the add ed compound. This study showed that it is possible to prove that urine has been adulterated with glycerol from other sources when the latter is present at a concentration of 15% of the total glycerol content.