Stabilizers detected in environmental samples with TCE may be diagnostic indicators for when the TCE was manufactured or possibly its application. Stabilizers are chemicals added to TCE to enhance its performance and longevity and include acid inhibitors (amines, epoxides, phenols, pyridines, trimethylamine, alcohols, alkyl halides, and azo-aromatic compounds), metals, antioxidants, and light inhibitors. Without stabilizers, degradation occurs, especially when TCE is used as a vapor degreasing solvent, in the presence of aluminum. Typical TCE stabilizer formulations include an acid acceptor, a metal stabilizer, and/or an antioxidant. These additives typically comprise about 0.1–0.5% of the TCE solvent, but concentrations can range as high as 2%. In vapor degreasing grades of TCE, concentrations at the higher end of the range are typical, and additional compounds are added to enhance thermal stability. Some stabilizers such as butylene oxide, epichlorohydrin, ethyl acetate, and methyl pyrrole are often present within 35% of their initial concentrations in spent or distilled TCE, thus offering the ability to detect them even if they are present initially at concentrations less than 1%.
