Recovery, TCDD

Figure 10. TCDD recovery in 10 gram human milk to which 10 gram (0.1 ppb) TCDD was added. Each trace represents 8% of the total residue.

Na2S04 after a water wash. The volume was adjusted, and an aliquot equivalent to 50 or 100 mg of soil was injected on to a 5% OV-225 GC column (I). Samples were amended at 1 and 5 ppb TCDD for recovery studies. 

Treatment of the extract with UV light (4) for 16 hours completely destroyed TCDD in the amended soil. The extract from the unamended soil was not changed by irradiation. Peaks close to the TCDD peak in retention time ( 0.2 min) were not altered. Recovery of ca. 100% was obtained when 5 ppb TCDD was added to the soil. A peak should be discernible at a concentration of 1 ppb as seen on the control core. However, background interference, even in the cleaned up residue, increased tremendously at the very low levels, and confirmation of a peak s identity was very difficult. 

Onuska and Terry [461] examined the extraction of tetrachlorodibenzodio-xin (TCDD) from sediments. They found that either C02 or N20 with 2% methanol as modifiers gave the highest recovery at 310 bar and 40 °C. They also studied the effect of extracting wet sediment, as opposed to the dry material, and found that when the sediment was moist, the recovery diminished by 20% for the same extraction time. However, the same efficiency could be achieved with the wet sediment if the 40 min extraction time was doubled. Soxhlet extraction of the same dried sediment with n-hexane/acetone (1 1) (150 ml) and 2,2,4-tri-methylpentane (25 ml) for 18 h was only around 65% of the SFE recovery. The Soxhlet extraction was considerably more variable (22-90%, n = 3), but since the Soxhlet actually recovered 90 % of the TCDD, this means that the method can be efficient but erratic. This variability was almost certainly a function of the heterogeneity of the matrix surface and/or the wettability of the sediment. 

Environmental applications of SFE appear to be the most widespread in the literature. A typical example is the comparison of extraction efficiency for 2,3,7,8 -tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) from sediment samples using supercritical fluid extraction and five individual mobile phases with Soxhlet extraction was made (101). The mobile phases, carbon dioxide, nitrous oxide, pure and modified with 2% methanol as well as sulfur hexafluoride were examined. Pure nitrous oxide, modified carbon dioxide and modified nitrous oxide systems gave the recoveries in the acceptable range of 80 to 100%. Carbon dioxide and sulfur hexafluoride showed recoveries of less than 50% under identical conditions. Classical Soxhlet recoveries by comparison illustrated the poorest precision with average extraction efficiencies of less than 65%. Mobile phase choice, still as yet a major question in the science of supercritical fluid extraction, seems to be dependent upon several factors polarity of the solute of interest, stearic interactions, as well as those between the matrix and the mobile phase. Physical parameters of the solute of interest, as suggested by King, must also be considered. Presently, the science behind the extraction of analytes of interest from complex matrices is not completely understood. 

TCDD-induced decrease in serum T4 in male Sprague-Dawley rats. The rats were gavaged once a week for 10 weeks with doses equivalent to approximately 0.003-1.6 g 2,3,7,8-TCDD/kg and this was followed by a 6-week recovery period. Serum T4 levels were significantly depressed with 2,3,7,8-TCDD doses of 0.03 g/kg in a dose-dependent fashion and remained low during the recovery period. Based on these results, the authors suggested that the ED50 for this dose-response is close to a total cumulative dose of 1 g/kg. 

Vitamin A (retinol) is essential for normal growth and cell differentiation, particularly for epithelial cells. 2,3,7,8-TCDD has been shown to decrease the storage of vitamin A in rodents. Decreased ability to store vitamin A (retinol) was found in rats and guinea pigs however, partial recovery of the retinol content by week 16 postexposure was reported only in rats. A single oral dose of 2,3,7,8-TCDD caused a 70% reduction in the liver storage of retinol in rats when measured 2 months postexposure (Thunberg et al. 

TCDD and related chemicals have been based for the most part on what was clinically feasible rather than on assays proven to be sensitive in animal studies (i.e., the antibody response to SRBC). Therefore, the lack of consistent or significant immunotoxic effects in humans exposed to 2,3,7,8-TCDD may be a function of both the type of assay and the immune status of the population studied. Furthermore, often the cohort exposure is not validated and the immune status has been examined long after exposure allowing for recovery from any immunotoxic effect that may have occurred shortly after exposure. 

Reported recovery and precision were generally good for measurements in air and gaseous waste emissions (Cooke et al. 1988 Fairless et al. 1987 Oehme et al. 1986), but severe sample loss can occur (Bingham et al. 1989 Rappe et al. 1988). Electron capture, negative ionization, low resolution MS has also been used to quantify CDDs in ambient air however, 2,3,7,8-TCDD is difficult to detect using this method and results must be confirmed with HRGC (Koester et al. 1992). 

Couture-Haws L, Harris MW, McDonald MM, et al. 1991b. Hydronephrosis in mice exposed to TCDD-contaminated breast milk Identification of the peak period of sensitivity and assessment of potential recovery. Toxicol Appl Pharmacol 107 413-428. 

The effluent from this column plus a 30 ml rinse containing the TCDD is passed directly onto a column containing 5g of activated basic alumina (Biorad, Inc.) which traps the TCDD. The hexane passing through the column is discarded. The TCDD is eluted from the column with 10 ml of methylene chloride. This alumina column transfers the TCDD from over 100 ml of hexane to 10 ml of methylene chloride allowing a much shorter time for solvent evaporation and the use of smaller glassware. Recovery of TCDD at this stage is in excess of 85%. 

The hexane solution contains the recovery standards, uCi2-1234-TCDD and 13Ci2-123789-HxCDD, at concentrations of 5.0 ng/pL, in a solvent other than tridecane or nonane (see Section 10.2). Depending upon the availability of materials, EMSL-LV will provide the solution. 

This solution contains 37Cl4-2378-TCDD at a concentration of 5 ng/pL (5 pg/mL) in tridecane (or nonane) and is added to all sample extracts prior to cleanup. The solution may be added at this concentration diluted into a larger volume of solvent (see Paragraph 9.7.1). The recovery of this compound is used to judge the efficiency of the cleanup procedures. 

Any time the retention time of either the 13Ci2-l,2,3,4-TCDD or 13Ci2-l,2,3,7,8,9-HxCDD recovery standards in any analysis varies by more than 10 seconds from its retention time in the most recent continuing calibration standard (see Paragraphs 7.3.2.3, 7.5.2.1 and 11.1.4)... 

The relative ion abundance criteria for PCDDs/PCDFs listed in Table 6 must be met for all PCDD/PCDF peaks, including the labeled internal and recovery standards in all solutions. The lower and upper limits of the ion abundance ratios represent a 15 percent window around the theoretical abundance ratio for each pair of selected ions. The 13Ci2-2,3,7,8-TCDD cleanup standard contains no 35C1, thus the ion abundance ratio criterion does not apply to this compound. 

For all calibration solutions, the retention times of the isomers must fall within the appropriate retention time windows established by the window defining mix analysis. In addition, the absolute retention times of the recovery standards, 13Ci2-1,2,3,4-TCDD and 13Ci2-1,2,3,6,7,8-HxCDD, shall not change by more than 10 seconds between the initial CC3 analysis and die analysis of any other standard. 

Prior to cleanup, all extracts are spiked with the 37Cl4-2,3,7,8-TCDD cleanup standard (Section 5.17). The recovery of this standard is used to monitor the efficiency of the cleanup procedures. Spike 5 pL of the cleanup standard (or a larger volume of diluted solution containing 25 ng of CL-2,3,7,8-TCDD) into each separatory funnel containing an extract, resulting in a concentration of 0.25 ng/pL in the final extract analyzed by GC/MS. 

NOTE When calculating the recovery of the 37Cl4-2,3,7,8-TCDD cleanup... 

After first emergency interventions, the main concern was the disposal of toxic waste from the ICMESA exploded reactor. In the spring of 1982, the vessel was emptied under strict safety precautions. The 41 barrels containing residues were transferred to destination. On the other hand, materials from recovery interventions, building demolition and soil removal were stored in two burrows placed in the towns of Seveso (tank A) and Meda (tank B). Tank A hosted material from the Seveso area and also ruins from ICMESA plant, for a total of about 200,000 m3. Tank B, located near the Certesa stream, hosted materials from the contaminated area placed north of ICMESA and TCDD contaminated mud originating from the Seveso purification plant. The total volume of material was about 80,000 m3. 

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