Analyses of volatile transformation products from additives in gamma-irradiated polyethylene packaging

Thermal desorption, followed by gas chromatography (GC) with mass spectrome try (MS) detection, has been found to allow the rapid identification of vol atile products resulting from the gamma -irradiation of stabilized, high de nsity polyethylene packaging and pure stabilizers. The stabilizers were tri s( 2,4-di-tert.butylphenyl) phosphite, octadecyl beta-(2,6-di-tert.butylphe nol)-propionate and 2, 4-di-tert.butylphenol, the latter resulting from pho sphite hydrolysis. Thermal desorption indicated the formation and release o f tert.butylbenzenes, such as 1,3-di-tert.butylbenzene upon gamma -irradiat ion of the HDPE. From a comparison of the products from gamma -irradiation of additive-free polyethylene, of various pure stabilizers and of related c ompounds, the tert.butylbenzenes were confirmed to result from the irradiat ion of the phosphite stabilizer and its phosphate conversion product. Therm al desorption off-line, in which volatiles released by a sample are trapped in sorbents for subsequent desorption in the heated GC inlet, is found to be a fast, extremely sensitive method that can be used to guide and supplem ent analyses of compounds extracted by foodstuffs.