Detection of radiation-induced hydrocarbons in irradiated fish and prawns by means of on-line coupled liquid chromatography gas chromatography

Radiation-induced hydrocarbons were analyzed in a fatty (halibut) and a lean fish (cod) as well as in a prawn species by on-line coupled liquid chromatography (LC)-gas chromatography (GC) combined with mass spectrometry. In irradiated halibut which is known to contain mainly saturated and monounsaturated fatty acids, all expected radiolytic alkanes, alkenes, and alkadienes could be detected. The yields of the Cn-1 and Cn-2:1 hydrocarbons were comparable to those found in irradiated lipids of terrestrial animals and plants. However, in cod and prawns which contain high levels of polyunsaturated fatty acids (PUFA), the Cn-1 hydrocarbons were found in concentrations which were up to 10 times higher whereas the Cn-2:1 products were again comparable to those of terrestrial animals and plants. The identification of radiation-induced hydrocarbons in fish lipids was achieved by transfer of the hydrocarbons from the LC column to the gas chromatographic column in fractions differing in their degree of unsaturation. For the first time, radiation-induced hydrocarbons with more than four double bonds generated from polyunsaturated fatty acids (20:4 omega 6 and 20:5 omega 3) could be identified.