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R D Weeren J Asshauer 《Journal of the Association of Official Analytical Chemists》1985,68(5):917-921
Quantitative analysis of tetrachlorodibenzo-p-dioxins (TCDDs) has gained increasing importance in the public domain. The analytical problem is complex because of the large number of interfering isomers and the extremely low limit of determination enforced by legislation. DAPA elaborated a procedure based on the latest published methods and on the existing experience of the collaborators. This procedure involves preseparation of the original sample on a silica column and cleanup by liquid chromatography (LC) on alumina. Alkaline saponification of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) esters seems to create artificial dioxins in the organic extract. Final determination is performed by capillary gas chromatography (GC)-low resolution mass spectrometry (MS). Final international collaborative work was carried out on 4 samples. Results were reported by 13 of 20 laboratories. Mean values ranged from 3.5 to 8.7 micrograms/kg. The interlaboratory reproducibilities ranged from 3.4 to 8.2 micrograms/kg (about 100% of the mean value). 相似文献
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Summary Every second month for 2 years a beech forest floor was treated with pentachlorophenol and 2,4,5-trichorophenoxyacetic acid each in two concentrations. The microbial biomass and its respiration activity in the three litter horizons were measured during this time and during a recovery period of 2 years after the treatment was stopped. The microbial biomass, mainly fungi, was decreased dose-responsively, as was the respiration rate. The doubling time of the fungal biomass was estimated to be about 50–100 days in the F horizon, and considering the natural decreases and recovery times observed, it is suggested, following Domsch et al. (1983), that a biomass decrease of 75%–93.75% is tolerable, a decrease of less than 75% is negligible, and a decrease of over 93.75% is critical. 相似文献
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The effect of 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) on the germination and seedling vigor of different crop seeds was tested. Seeds of rice, maize, sorghum, finger millet, and horse gram were comparatively more tolerant to the chemical with no marked effect up to a concentration of 200 mg 2,4,5-T L(-)(1) as tested by the filter paper method. Tomato and brinjal (egg plant) were highly susceptible. Even at 5 and 10 mg 2,4,5-T L(-)(1), marked reduction in the germination and seedling vigor of tomato and egg plant, respectively, was observed. At 20 and 30 mg L(-)(1), the germination of tomato and egg plant seeds, respectively, were completely inhibited on filter paper, whereas the inhibitory concentrations in soil was 40 mg 2,4,5-T kg(-)(1) soil. Several abnormalities were observed in the chemically affected seedlings. Protease activity of the seeds germinating in the presence of the chemical was drastically reduced. Bioremediation of the chemically contaminated soil with Burkholderia cepacia AC1100, by inoculation of the soil 7 days before sowing the seeds, completely protected the seeds, resulting in normal germination and an improved seedling vigor. 相似文献
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