David L. Stalling

Residues of Polychlorinated Dibenzo-P-Dioxins and Dibenzofurans in Laurentian Great Lakes Fish

Fish from the Laurentian Great Lakes, and related rivers, and lakes were examined for residues of polychlorinated biphenyls (PCBs), dibenzofurans (PCDFs), and dibenzo-p-dioxins (PCDDs). Patterns of PCDF residues were more complex than those of PCDD residues, and were dominated by isomers having 2,3,7,8-chlorine substitution. PCDF residues were presented in samples from all of the Great Lakes and exceeded 100 pg/g in fish from Lakes Ontario and Huron, Michigan, and Saginaw Bay. A composite sample of fish from the Tittabawassee River (Michigan) contained 290 pg/g of PCDFs and 223 pg/g of PCDDs. Ratios of PCDFs to PCBs ranged from 1 to 20 X 106. Attempts to correlate PCDF residue levels in biological samples with PCDF concentrations in PCB preparations are complicated by an apparent preferential retention or accumulation of 2,3,7,8-substituted congeners. The PCDF concentrations in a fish from Lake Siskiwit (on Isle Royale, Lake Superior) were the lowest detected in this study (15 pg/g). Fish from Lakes Huron and Ontario, the Tittabawasee River and Saginaw Bay contained the highest concentrations of 2,3,7,8-TCDF. In another river system, the Housatonic River, Massachusetts, the composition of PCDD and PCDF residues in sediments differed radically from residues in fish from this river.

Negative chemical ionization studied of human and food chain contamination with xenobiotic chemicals.

Negative chemical ionization mass spectrometry with a mixture of isobutane, methylene chloride, and oxygen as the reagent gas has been used to explore contamination of environmental substrates with xenobiotic chemicals. The substrates in question, fish tissue, human seminal plasma, and human adipose tissue, were cleaned up by one of the following three cleanup procedures: (1) continuous liquid-liquid extraction steam distillation; (2) gel-permeation chromatography; and (3) adsorption on activated carbon followed by elution with toluene. The third procedure was used only for the examination of planar polychlorinated aromatic hydrocarbons in environmental samples. Using these techniques, we have found evidence for contamination of fish samples with polychloronaphthalenes, polychlorostyrenes, polychlorobiphenyls, polychlorodibenzofurans, and polychlorodibenzodioxins among other chemicals. The polychlorodibenzodioxins appeared only in the spectra of extracts of fish obtained from the Tittabawassee River at Midland Michigan. The polychlorodibenzofuran ions appeared in NCI mass spectra of fish that were significantly contaminated (above 2 ppm) with polychlorobiphenyls. Toxic substances occurring in human seminal plasma included pentachlorophenol, hexachlorobenzene, DDT metabolites, and polychlorobiphenyls. We have investigated toxic substances in human seminal plasma because of the apparent decrease in sperm density in U.S. males over the last 30 years. Results of screening human adipose tissue for contamination with xenobiotic chemicals have been largely coincident with result of the EPA human monitoring program. Polychlorobiphenyls, DDT metabolites, nonachlor, and chlordane have appeared in most samples examined. Detection limits for all of these chemicals were of the order of 1 ppb.

Hexachlorobenzene (HCB) residues in fish

Analysis of fish collected by the U.S. Fish and Wildlife Service for the fall 1970 National Pesticide Monitoring Program detected the presence of a compound eluting with, and subsequently identified incorrectly as B-benzenehexachloride. This compound was frequently observed when Florisil cleanup was used in the analysis of organochlorine residues in fish. Examination of selected sample extracts by gas chromatography-mass spectrometry (GC-MS), however, indicated that the compound was really hexachlorobenzene (C6CI 6 or HCB). After identification, residue levels were determined in fish collected from waters within the United States.

Use of pattern recognition in the evaluation of PCDD and PCDF residue data from GC/MS analyses

Abstract We used the chemometric approach with SIMCA (soft independent modeling by class analogy) multivariate statistical programs, based on principal components modeling to examine complex PCDD and PCDF residues in environmental samples. This approach was employed to determine the acceptability of measured tetrachloro isotope ratios when three ion intensities, m+., (m+2)+., and (m+4)+., were measured by monitoring multiple ions. Isotope labeled internal standards and native compounds were examined. Principal components contain information about similarity of samples and variability in measurement. The data for the observed ion ratios were merged with the theoretical ion ratios and a calculated set of data that deviated from the theoretical values over a range of +/− 10 % for each ion pair. Thus the plot of principal components sample scores contains the error boundaries for accepting data that meet this quality assurance criterion and identifies the samples and calibration data that are within the acceptable range. In addition, GC/MS peaks having more than one constituent with different degrees of chlorination were readily detected. Residues of PCDDs in eggs of herring gulls ( Larus argentatus ) collected from colonies in the Great Lakes region in 1981 – 1984 were measured by GC/MS. Principal components modeling of the normalized residue data demonstrated that the sample residue profiles differed according to the samples origin and that sample profiles remained remarkably similar over the 4-year period in which the samples were collected.

Applications and results of analytical methods used in monitoring environmental contaminants

Techniques being developed to purify, fractionate, and classify complex organic chemical residues will simplify the detection of these residues and provide more comprehensive data about them. These techniques include an integrated series of chromatographic processes, new technology in mass spectrometry, advances in glass capillary-gas chromatography, and chemical derivatization. Gel permeation chromatography increases the efficiency of sample cleanup. Additional cleanup and selective separation of residues are achieved by adsorption chromatography (Florisil, silica gel, and carbon foam). An important finding which results from the use of this methodology is the identification of potentially toxic chlorinated dibenzofurans in fish tissue. An analytical scheme for isolating and detecting acidic pollutants was developed: derivatization of phenols and other acidics to pentafluoro benzyl ethers enhances their chromatography and detection. Partial automation of the sample cleanup and enrichment of residues reduces the time required for analyses, and the new separation techniques increase the number of components that are identifiable from a tissue matrix.

ISOLATION AND ANALYSIS OF POLYCHLORINATED DIBENZOFURANS IN AQUATIC SAMPLES

ABSTRACT Polychlorinated-dibenzofurans (PCDFs) and -dibenzo-p-dioxins (PCDDs) are isolated from fish and other aquatic samples and separated from interfering substances (especially PCBs, polychlorinated hydroxybiphenyls, phenoxyphenols, and diphenyl ethers) in two series of sequential chromatographic processes. The first chromatographic process involves sequential passage of the extracted oil through a column containing a segment of KOH-treated silica gel above another segment of silica gel; in the second process the eluate is passed through another column that contains carbon dispersed on glass fibers. The carbon adsorbs planar aromatic components from the eluate of the first column and neutral, non-aromatic contaminants are efficiently eliminated. The PCDF and PCDD residues are recovered from the carbon by reverse elution with toluene. The sample is then applied to two adsorbents in series in a column containing CsOH-treated silica gel and H 2 SO 4 -impregnated silica gel. The eluate from this column is applied directly to a column containing alumina for further fractionation of the planar contaminants. The PCDFs are identified and quantified by gas chromatography/mass spectrometry in the methane chemical ionization negative ion mode. Analyses of fat samples by gel permeation chromatography combined with carbon enrichment procedures revealed the presence of numerous PCDF isomers, including 2,3,7,8-tetra-, and 2,3,4,7,8-penta-chlorodibenzofuran. The PCDF content of the samples examined was about 3000 pg/g in fat from a snapping turtle (Hudson River) and 30 pg/g in fat from a grey seal (Baltic Sea). The concentration ratio of PCBs to PCDFs was on the order of 10 5 to 10 6 .