Identification of cis- and trans-1,1,2,3,4-pentachloro-4-[1-methylethoxy]-1,3-butadiene residues in Mississippi River fish.

The cis- and trans-isomers of 1,1,2,3,4-pentachloro-4-[1-methylethoxy]-1,3-butadiene have been identified as contaminants in fish caught from the Mississippi River at St. Louis, MO, and as far as 150 miles south of that location. Up to 0.1 ppm of the cis-isomer and 0.8 ppm of the trans-isomer were determined by using a method based on the AOAC multiresidue method for detecting organochlorine and organophosphorus pesticides. In tests of the modified AOAC method on spiked fish, both isomers were quantitatively recovered (95-106%). A mixture of the cis- and trans-isomers was synthesized by reacting hexachlorobutadiene with sodium isopropoxide. Separation of the reaction products by Florisil column chromatography provided reference standards of the individual isomers for identification and quantitation of the residues. The stereospecificity of the synthesis reaction and the infrared and mass spectral data used to verify the structures of the products are discussed.

Identification of O,O-dialkyl-S-methylphosphorodithioate residues in fish.

O,O-Dialkyl-S-methylphosphorodithioates were found in Mississippi River buffalo fish caught near several chemical plants and oil refineries in Hartford and Wood River, IL. These chemicals, which have not been previously recognized as environmental or food contaminants, were identified and quantitated by a procedure similar to the AOAC multiresidue method for organochlorine and organophosphorus pesticides, using gas chromatography (GC) with flame photometric detection (FPD). The key to their identification was a GC/FPD retention time pattern that was virtually the same as that for the diazomethane reaction products of a commercial zinc dialkyl dithiophosphate motor oil additive. GC/mass spectrometry (MS) showed that the compound producing the largest GC/FPD peak contained butoxy groups. The identification of this compound as O,O-di(2-methylpropyl)-S-methyl-phosphorodithioate (Compound C) was confirmed by GC/MS analysis by comparison with the authentic material. The buffalo fish contained 0.15 ppm Compound C and 0.5 ppm total O,O-dialkyl-S-methylphosphorodithioates. Subsequent analyses of fish from other areas showed that these contaminants were not limited to the Hartford-Wood River area. Lower residue levels of Compound C, ranging from 0.01 to 0.05 ppm, were found in fish from the Mississippi River at Sauget, IL, and from the Delaware River and Newark Bay in NJ.

Gas chromatographic determination of electron capture sensitive volatile industrial chemical residues in foods, using AOAC pesticide multiresidue extraction and cleanup procedures.

Electron capture (EC) gas chromatographic (GC) parameters have been developed for determining some of the more volatile industrial chemicals that can be determined by the AOAC multiresidue method for organochlorine and organophosphorus pesticides with modified GC operating conditions. Retention times relative to pentachlorobenzene are reported for 143 industrial chemicals, pesticides, and related compounds on OV-101 GC columns at 130 degrees C. Also reported for most of the compounds are recoveries from fortified samples carried through the AOAC extraction and cleanup procedures for fatty and/or nonfatty foods, Florisil elution characteristics, and GC relative retention times on mixed OV-101 + OV-210 columns at 130 degrees C. Our laboratory has used the modified EC/GC parameters with the AOAC multiresidue extraction/cleanup procedures to determine many volatile halogenated industrial chemical contaminants in foods, chiefly in samples of fresh-water fish. Other modifications of the AOAC method are described to improve the tentative identification and quantitative measurement of these volatile residues.

Identification of chlorinated nitrobenzene residues in Mississippi River fish.

Residues of lower chlorinated nitrobenzenes have been found at levels up to about 1 ppm in 8 samples of Mississippi River fish. Electron capture gas chromatography (EC/GC) was used for determination after extraction and cleanup using a procedure based on the AOAC multiresidue method for organochlorine and organophosphorus pesticides in nonfatty foods. The residues found included 2-, 3-, and 4-chloronitrobenzene and 2,3- and 3,4-dichloronitrobenzene; identity was confirmed by GC/mass spectrometry. GC retention times for 15 monochloro-through pentachloro-substituted nitrobenzene congeners were determined with OV-101 and mixed OV-101 + OV-210 columns at 130 degrees C. In studies of the nonfatty food extraction and cleanup procedures of the AOAC method, recoveries of 15 chlorinated nitrobenzenes from spiked fish samples ranged from 68 to 116%. GC of cleaned up fish extract aliquots equivalent to 20 mg sample allowed quantitation of individual congeners at levels of about 0.025 and 0.005 ppm with 3H and 63Ni EC detectors, respectively. The contamination of Mississippi River fish with chlorinated nitrobenzenes appears to be localized in a 150 mile section of the river extending from St. Louis, MO, to Cape Girardeau, MO; no chlorinated nitrobenzenes (less than 0.005 ppm) were detected in Mississippi River fish caught above or below this region of the river or in fish from the lower Missouri River, which joins the Mississippi River near St. Louis.

Screening of fresh water fish extracts for enzyme-inducing substances by an aryl hydrocarbon hydroxylase induction bioassay technique.

A sensitive biological test to detect the presence of certain contaminants, such as highly toxic halogenated dioxins, dibenzofurans, and biphenyls in foods, was applied to extracts of fresh water fish that had been prepared by a food extraction-cleanup procedure developed by the Food and Drug Administration for pesticides and industrial chemicals. Aryl hydrocarbon hydroxylase (AHH) activity in a rat hepatoma cell line was used as the biological detection system for residues that induce enzyme activity. The induction of AHH activity by the extracts was compared with a standard AHH-induction curve for the most active compound known, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and results were computed as TCDD equivalents. Several dilutions of fish extracts were used to produce AHH-induction curves from which an optimal dose-response range was determined and used to estimate TCDD equivalents. Cleaned-up extracts of fish obtained from different water bodies in the United States were examined for AHH activity. The samples which had low levels of polyhalogenated contaminants produced low biological activity, while a higher activity was obtained from fish that contained higher levels of polyhalogenated contaminants. The results suggest that the fish extracts can be screened for AHH inducers before chemical analysis.

Analytical characteristics of late-eluting halogenated flame retardants.

The analytical characteristics of halogenated flame retardants were studied. Suitable electron capture gas-liquid chromatographic conditions were developed, and retention times and sensitivity responses were obtained. The behavior of these industrial chemicals through the AOAC multiresidue method for nonfatty foods was studied using fish as the test substrate. Of the 24 flame retardants investigated, 23 were recovered (85-110%) using the AOAC method.