Dioxin sampling

Helpful discussions with David N. Lincoln are acknowledged with pleasure. The 1,6-dibenzo-p-dioxin sample was kindly supplied by J. H. Vinopal and J. E. Casida, Division of Entomology, University of California, Berkeley, Calif. 

The o-dichlorobenzene extracts were combined and analyzed by GLC. Four peaks were observed under standard GLC conditions in the 10 to 15 min retention time range which is characteristic of hexachloro-dibenzo-p-dioxins (sample 1 in Table IV). The mixture was fractionally sublimed (120° to 175°G/1 mm). The major crop was harvested at 175 °G and recrystallized from anisole. Analysis of this material by GLG indicated that two isomeric hexachlorodibenzo-p-dioxins were present (sample 2). Overall yield (1.5 grams) of the product was 1-3% at 99+% purity, as determined by GLG and mass spectrometry. 

Participant Dioxin sample Mixed sample Sediment extract Sediment ... 

The interlaboratory results obtained from the analysis of defined standard solutions, but also from the analysis of sediment extracts prepared either by the coordinator of the study or by the participants themselves, also provide a measure of the variation between laboratories. The results show that the interlaboratory reproducibility ranges from 6.5% for the defined dioxin sample to 27.9% for the sediment sample extracted by the participants themselves. As was mentioned before, the reproducibility for this last sample is relatively high and most presumably due to the introduction of extra handlings (extraction and cleanup) to the total procedure. In addition, the fact that not all the participants had prior experience with the extraction protocol to be used could have added to the increase in variability of the process. Furthermore, the dilution factor was not dictated. This also introduces a certain degree of variation. For the reproducibility of the DR CALUX bioassay itself and not caused by differences in operating extraction conditions, the maximum variation between laboratories was observed to be 18.0%. The results for the sediment extract samples can also be used to estimate the method variability for extracts, that is, based on samples of unknown composition. Again, given the intra-as well as the interlaboratory variations observed in this study, it appears justified to conclude that the standard deviation of the means provides a reasonable estimate of the method variability, based on the overall aver-... 

Whittle DM, Mageau C, Duncan RK, et al. 1993. Canadian national dioxin sampling program ... 

Apart from GPC with Bio-Beads, there are other automated clean-up approaches. Although GPC has several advantages, Focant and co-workers claimed that for the high-fat-content samples (4 g lipids) required in dioxin analysis, GPC suffered from several practical limitations and therefore could not be performed 100% automatically (59). Consequently, new high-capacity disposable silica (HCDS) columns were developed for the Power-Prep system. The combination of PLE and Power-Prep clean-up allowed 10 dioxin samples to be analyzed in 48 hrs. 

However, the report shows that the methods are completely unreliable with respect to negative and lowest level samples. The number of samples of each type examined and the percent of negative (no added dioxin) samples reported positive (false positives) are given in Table 3. 

A second sampling program in Southern California sampled for polychlorinated dioxins and polychlorinated dibenzofurans at seven locations (9). Because of the semivolatile nature of these compounds, a tandem sampler was used with a glass fiber filter to collect the particulate-associated compo-... 

Toxic equivalency factors (TEFs) are estimated relative to 2,3,7,8-TCDD, which is assigned a value of 1. They are measures of the toxicity of individual compounds relative to that of 2,3,7,8-TCDD. A variety of toxic indices, measured in vivo or in vitro, have been used to estimate TEFs, including reproductive effects (e.g., embryo toxicity in birds), immunotoxicity, and effects on organ weights. The degree of induction of P450 lAl is another measure from which estimations of TEF values have been made. The usual approach is to compare a dose-response curve for a test compound with that of the reference compound, 2,3,7,8-TCDD, and thereby establish the concentrations (or doses) that are required to elicit a standard response. The ratio of concentration of 2,3,7,8-TCDD to concentration of test chemical when both compounds produce the same degree of response is the TEF. Once determined, a TEF can be used to convert a concentration of a dioxin-like chemical found in an environmental sample to a toxic equivalent (TEQ). 

PCDDs and PCDEs, together with coplanar PCBs, can express Ah-receptor-mediated toxicity. TCDD (dioxin) is used as a reference compound in the determination of TEFs, which can be used to estimate TEQs (toxic equivalents) for residues of PHAHs found in wildlife samples. Biomarker assays for Ah-receptor-mediated toxicity have been based on the induction of P450 lAl. TEQs measured in field samples have sometimes been related to toxic effects upon individuals and associated ecological effects (e.g., reproductive success). 

Purification of the radioactive tracer was modified to include a fractional sublimation before a single extraction—recrystallization cycle to conserve the tracer material. Microgram samples were prepared in melting point capillaries for assay by mass spectroscopic analysis (Table III), made by direct probe injection of the sample into the ion source (18). The probe was heated rapidly to 200°C, and mass spectra were obtained during vaporization of the sample. Tri-, tetra-, and pentachlorodibenzo-p-dioxins vaporized simultaneously with no observed fractionation. 

Mass Spectrometry. The mass spectra were obtained on a CEC 21-llOB mass spectrometer with the batch inlet system maintained at 250°C to assure complete vaporization of the samples. Sensitivity factors for quantitative analysis were obtained from standards of di-, tetra-, hexa-, and octa-chlorodibenzo-p-dioxin. The factors for the intermediate chlorinated species were estimated by interpolation. The analyses were based... 

In addition, an interesting, although negative, result has come from powder diffraction studies of the hexachloro compounds. We have examined Debye—Scherrer photographs of several samples known to contain predominantly hexachlorodibenzo-p-dioxins and have identified the patterns of at least three crystalline phases therein. (There are 10 possible isomers of hexachlorodibenzo-p-dioxin.) These patterns have been checked carefully against the calculated d-spacings and intensities of the 1,2,3,7,8,9-hexa isomer described by Cantrell, Webb, and Mabis (I) and also against an observed pattern supplied by Cantrell and believed to be from the low temperature phase of the same material. Yet to date we... 

Acute Lethality. Samples of 2,7-dichlorodibenzo-p-dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin, hexachlorodibenzo-p-dioxin, and octachloro-dibenzo-p-dioxin were evaluated for acute oral lethality in the following animals. 

The toxicity of chlorodibenzodioxins other than those evaluated in this study has not been reported. Purified samples of trichloro-, penta-chloro-, and heptachlorodibenzo-p-dioxin which are free of tetrachloro-and hexachlorodibenzo-p-dioxin need to be synthesized for study. However, heptachlorodibenzo-p-dioxin cannot be highly toxic since studies on octachlorodibenzo-p-dioxin containing several percent of heptachloro-dibenzo-p-dioxin have tested the same as the pure product. 

Oral treatment of pregnant dams with 0.25 /xg (or more) /kg/day of 2,3,7,8-tetrachlorodibenzo-p-dioxin for 10 days during gestation resulted in adverse effects on rat development. No adverse effects were seen at the 0.125 ju,g/kg/day. When C-2,3,7,8-tetrachlorodibenzo-p-dioxin (2.99 fjLc/mg) was given at 2 /xg/kg/day there was activity, primarily in liver and to a lesser extent, in fat and brain. When a single oral dose of 200 /Ag/kg was administered on gestation days 16, 17, or 18 and was followed 6 hours later with tissue sampling, the label was also observed in the fetus and placenta. Placenta had approximately twice as much label as the fetus. 

An environmental protocol has been developed to assess the significance of newly discovered hazardous substances that might enter soil, water, and the food chain. Using established laboratory procedures and C-labeled 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), gas chromatography, and mass spectrometry, we determined mobility of TCDD by soil TLC in five soils, rate and amount of plant uptake in oats and soybeans, photodecomposition rate and nature of the products, persistence in two soils at 1,10, and 100 ppm, and metabolism rate in soils. We found that TCDD is immobile in soils, not readily taken up by plants, subject to photodecomposition, persistent in soils, and slowly degraded in soils to polar metabolites. Subsequent studies revealed that the environmental contamination by TCDD is extremely small and not detectable in biological samples. 

Dioxin Residues in Lakeland Sand and Bald Eagle Samples... 

Tetrachlorodibenzo-p-dioxin (TCDD) is a contaminant in 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) which may occur in the manufacturing process. Before 1971 some samples of 2,4,5-T contained from 2-50 ppm TCDD (i) in the technical acid. Highest concentrations of TCDD occurred before 1968. 

No dioxin residues were detected at a level of 0.05 ppm TCDD, the lower limit of detection for most pesticides in tissue samples run by the Patuxent Wildlife Research Center. The non-detection of dioxin residues can imply several things ... 

Heat Stability of 2,3,7,8-Tetrachlorodibenzo- -dioxin. A sample boat containing 1-3 mg of 2,3,7,8-tetrachlorodibenzo-p-dioxin was placed in a Sargent Tube Heater (Model J-807) which contained a 1/2 inch i.d. quartz tube. Air was aspirated through the tube at a velocity of 0.02 ft/sec. This velocity gave a residence time of 21 sec. (Residence time was extended by connecting a second heater in series with the first.)... 

Stability of 2,3,7,8-Tetrachlorodibenzo- >-dioxin Towards Air Oxidation Under Simulated Conditions. Air was bubbled through two borosilicate glass gas absorption bottles equipped with fritted glass bubblers. The first bottle contained 1-octanol for presaturation of the air, and the second bottle contained 1-octanol solutions of the dioxin treated as follows (1) octanol only, (2) octanol mixed with 74-105ju, glass beads to increase the surface area, and (3) octanol mixed with magnesium oxide to simulate a basic soil. The original solution and the sample solutions were scanned with a UV spectrophotometer at various time intervals for 4 days to determine the stability of 2,3,7,8-tetrachlorodibenzo-p-dioxin. 

Light Source Exposure Time Oclachlorodibenzo-p-dioxin Formed Based on Total Sample Weight... 

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