Analysis of halogenated fatty acids in fish lipids by gas chromatography with electrolytic conductivity detection and mass spectrometry

Abstract: Organochlorine compounds in fish lipids were characterized by studying the partitioning of chlorinated species into acidic and neutral fractions before and after hydrolysis of the lipids, and after transesterification to fatty acid methyl esters (FAMEs). Chlorinated fatty acids (Cl-FAs) were found to be the major organochlorine components in the fish lipids. Approximately 90% of the extractable organically bound chlorine (EOCl) in the lipids of eel, caught in a fjord polluted by pulp mill waste waters, could be accounted for by chlorine in Cl-FAs, by using gas chromatography (GC) with electrolytic conductivity detection (ELCD). An enrichment method for chlorinated FAMEs was developed, in order to study organochlorine compounds in lipids of fish containing low concentrations of EOCl. The enrichment was achieved by the removal of unsubstituted, straight-chain FAMEs and polyunsaturated FAMEs as their urea complexes and silver ion complexes, respectively. Following the enrichment, Cl-FAs could be detected by GC/ELCD in the lipids of several other fish species. Dichloroalkanoic, dichloroalkenoic, and tetrachloroalkanoic acids in the eel lipids were identified as the corresponding methyl esters by using mass spectrometry (MS). High resolution MS was used for confirmation. Halogenated fatty acids (X-FAs) also contributed significantly to the organohalogen compounds in muscle lipids and roe lipids of sockeye salmon from Alaska. X-FAs bound in triacylglycerols from salmon muscle were catabolized and transferred to roe to approximately the same extent as normal fatty acids during a spawning migration. It was also found that Cl-FAs were transferred from salmon to another fish species.