Huiling Mu

Identification of chlorinated fatty acids in fish lipids by partitioning studies and by gas chromatography with Hall electrolytic conductivity detection

Abstract Chlorinated compounds in fish lipids [determined by neutron activation analysis as extractable, organically bound chlorine (EOCl)] were characterized by liquidliquid extractions after enzymatic hydrolysis and after forming fatty acid methyl esters (FAMEs). Most of the chlorinated compounds in lipids from four different fish samples could be hydrolysed. Comparison with results of methanolysis of two of the fish lipids indicated that chlorinated fatty acids made up the major portion of EOCl. Using gas chromatography (GC) with electrolytic conductivity detection (ELCD), chlorinated compounds were found among FAMEs of ee] lipids containing 1200 ppm of EOCl. Approximately 90% of EOCl was detected by GC-ELCD. The GC-detectable compounds are suggested to be methyl esters of chlorinated fatty acids and 9,10-dichlorostearic acid was tentatively identified after co-injection of the synthesized compound.

Gas Chromatographic and Mass Spectrometric Identification of Tetrachloroalkanoic and Dichloroalkenoic Acids in Eel Lipids

Chlorinated fatty acid methyl esters, transesterified from the lipids of eel (Anguilla anguilla ; obtained from the receiving waters of a chlorine bleaching pulp mill), were studied by gas chromatography (GC) using electrolytic conductivity detection and mass spectrometry (MS) with electron impact and ammonia positive-ion chemical ionization. GC retention indices and column difference values in combination with GC/MS demonstrated the presence of isomers of methyl dichlorotetradecenoate, methyl dichlorohexadecenoate, methyl dichlorooctadecenoate and methyl tetrachlorotetradecanoate. Isomers of methyl threo, threo-tetrachlorooctadecanoate were identified by co-injection of the eel sample and synthesized reference compounds. The results were confirmed by ammonia positive-ion chemical ionization high-resolution selective-ion monitoring of the ammonium adduct molecular ions.

HALOGENATED FATTY ACIDS : I. FORMATION AND OCCURRENCE IN LIPIDS

Abstract Chlorinated fatty acids have been found to be major contributors to organohalogen compounds in fish, bivalves, jellyfish, and lobster, and they have been indicated to contribute considerably to organohalogens in marine mammals. Brominated fatty acids have been found in marine sponges. Also, chlorinated lipids have been found in meat exposed to hypochlorite disinfected water, and in chlorine-treated flour and in products made from such flour. Following exposure to chlorine bleached pulp mill effluents, aquatic organisms may have elevated concentrations of chlorinated fatty acids in their lipids. However, a natural production of halogenated fatty acids is also possible. In this paper we summarize the present knowledge of the occurrence of halogenated fatty acids in lipids and suggested ways of their formation. In Part II (Trends Anal. Chem. 16 (1997) 274) we deal with methods of their determination.

Halogenated fatty acids: II. Methods of determination in lipids

Abstract Halogenated fatty acids are the major contributors to organohalogen compounds in lipids of marine mammals, fish, and bivalves. For the initial characterization of these recently noticed compounds, a determination of the halogen concentration has usually been combined with some lipid isolation and separation method. This review covers separation by solid phase chromatography, gel permeation chromatography, and liquid-liquid extraction, followed by halogen determination. All studies performed according to this outline have indicated that the major organohalogen compounds are chlorinated fatty acids bound in different lipids. For the detection and identification of individual, halogenated fatty acid methyl esters (FAMEs) liberated from the lipids, gas chromatography (GC) has been employed together with detection methods such as electron capture detection, electrolytic conductivity detection (ELCD), atomic emission spectrometry, and mass spectrometry. For most environmental samples, chlorinated FAMEs must be enriched prior to GC. ELCD is a useful detection method for indicating halogenated FAMEs in the chromatograms, and tentative identification of the halogenated species can be obtained by calculation of retention indices. For closer identification of halogenated FAMEs, mass spectrometry (MS) is very useful, in particular when employing the chemical ionisation mode. MS identification, however, is highly facilitated if halogenated species are first indicated by element-selective methods.

Occurrence of halogenated fatty acids in bivalve lipids

Environmental pollutants account for 1–3% of the extractable, organically bound chlorine (EOCl) found in bivalve lipids. In this work, bivalve lipids were converted to fatty acid methyl esters (FAMEs). The EOCl in the FAMEs and in acidic compounds was examined after liquid-liquid extraction using neutron activation analysis for chlorine determination. Gas chromatography with halogen selective, electrolytic conductivity detection (GC/ELCD) was employed to study the occurrence of halogenated FAMEs. Following esterification, most of the EOCl was recovered in the FAME-containing fraction. However, silica gel chromatography showed that more than 50% of the EOCl consisted of compounds of higher polarity than the chlorinated FAMEs normally found in fish extracts. By using GC/ELCD, up to 25% of the EOCl was detected as halogenated fatty acids. A complex pattern of halogenated fatty acids was found in bivalves from the Baltic Sea. This pattern was simplified to one consisting of only a few halogenated fatty acids in bivalves from West Scandinavian waters. These acids seem to persist in the ecosystem. It is possible that up to 40% of the EOCl remained in a brown, organic material of polar character that was coextracted with the FAMEs.

Response factors of organochlorine compounds in the electrolytic conductivity detector

In our previous studies we have used electrolytic conductivity detection (ELCD) in the selective analysis of chlorinated fatty acids in marine samples. In order to determine the chlorinated fatty acids quantitatively, we studied the ELCD response factors (RFs) of chlorinated fatty acids and compared them with those of other chlorinated compounds. We also studied the effect of reactor temperature and total gas flow-rate on the RFs. The ELCD RFs of different organochlorine compounds varied significantly at a reactor temperature of 600°C. The variation was reduced at reactor temperatures higher than 850°C. At low reactor temperatures, the RFs of methyl esters of chlorinated fatty acid were much higher than those of the other compounds. Although the gas flow in the reactor was laminar, diffusion was still rapid enough not to cause the varied RFs. Nitrogen-containing chlorinated compounds had lower RFs than compounds without nitrogen, owing to a neutralization of hydrogen chloride by ammonia.