Abstract
Micro-agglomerate corks, made by agglutination of cork granulate through the addition of different adhesives, represent an important slice of the market of cork stoppers. Binder glues which are polyurethane- or butadiene-based have been used since they have strong agglomerating effect. Unfortunately, polyurethane-based glues can have isocyanide end group compounds which can migrate into the wine. 2,4-toluene diisocyanate (2,4-TDI) and 2,6 toluene diisocyanate (2,6-TDI), can be found in adhesive and could migrate into wine. A simple ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) method for the determination of these active ingredients (a.is.) in wine has been developed. The method has been validated under Eurachem CITAC guidelines (Cooperation on International Traceability in Analytical Chemistry). Instrument limit of detection (LOD) and to a limit of quantification (LOQ) for 2,6 TDI and 2,4 TDI were 0.42 and 0.39 μg/L, and 1.72 and 1.57 μg/L, respectively. Four different solvents applied for recoveries showed quite different rates ranging for 2,6 TDI and 2,4 TDI from 17.96 to 88.53 %, and 40.08 to 99.18 %, respectively. Real sample analysis showed low residue levels, especially of 2,6 TDI, with values always below the LOQ. The data reported on real samples allowed to establish that from a risk management purpose, no toxicology risk can be accomplished.
Highlights
The use of cork as stoppers is traced back to the ancient Romans; in the Greek and Roman world, it was customary to use it for the closure of amphorae (Denecker and Vandorpe 2007).In a bottle of wine, the type of closure represents one of the most important and delicate parts
M/z 104 and m/z 132 were used as quantifying ions for 2,6 toluene diisocyanate (TDI) and 2,4 TDI, respectively, while m/z 147 was used as qualifying ion for both a.is (Table 1)
The matrix effect, evaluated at 0.8 μg/L, showed that the wine matrix caused a high decrease of the signal of 2,6 TDI of almost 86% while did not affected the detection of 2,4 TDI (Table 1) (Fig. 2)
Summary
The use of cork as stoppers is traced back to the ancient Romans; in the Greek and Roman world, it was customary to use it for the closure of amphorae (Denecker and Vandorpe 2007).In a bottle of wine, the type of closure represents one of the most important and delicate parts (especially in the case of fine and aging wines). Screwcaps have been initially used in the whisky industry with excellent results, and have been introduced in the wine market in the late 1950s in France, after replacing a thin cork layer underneath the cap with neutral polyvinylidene dichloride (PVDC) (Courtney 2001). Their use has been justified from the assertion that they do not allow oxygen to enter the bottle and ensures that the wine remains crisp and wellpreserved; no corkscrew is required for extracting the closure. A major benefit of synthetic cork is the absence of cork taint (TCA) caused by the different fungi species that lives in natural cork trees (Prak et al 2007)
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