PubMed · 90898
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P D Stolley, J L Davies. 1979-10-13. Oestrogen-replacement therapy.. https://doi.org/10.1016/s0140-6736(79)92154-8
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The mechanism and pathway through which 2,4-dinitrotoluene (DNT) is reduced with elemental iron were investigated through batch experiments performed utilizing the same iron surface area, with high-purity iron powder and Master Builders scrap iron. In addition to different kinetics and adsorption patterns, the distribution of two intermediates, 4-amino-2-nitrotoluene (4A2NT) and 2-amino-4-nitrotoluene (2A4NT), contrasted sharply. This suggests that different mechanisms are involved in DNT reduction with pure iron and scrap iron. We hypothesized that exposed graphite in scrap iron transferred reductants from iron to adsorbed nitroaromatic molecules. This hypothesis was supported by an experiment conducted using two-compartment dialysis cells in which ONT and pure iron powder were separated by a graphite sheet. Results indicate that graphite-mediated, indirect reduction of DNT occurred primarily through reduction of the ortho nitro group to form 2A4NT, whereas DNT reduction at the iron (hydr/oxide) surface occurred via para nitro reduction to give 4A2NT. Based on pH and product analysis, atomic hydrogen probably accounted for most of the reducing equivalents that passed through the graphite, reacting with adsorbed DNT mainly through ortho nitro reduction. In contrast, electron was a minor fraction of the reducing equivalents, reducing DNT mainly through para nitro reduction. The implications of graphite as a reaction site and conductor of electron and atomic hydrogen are discussed with respect to treatment processes involving iron.
Tobacco-specific nitrosamines (TSNA) are among the most important and abundant strongly carcinogenic agents in unburned tobacco. It has been established that 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induces lung tumors in rodents independent of the route of administration. N'-Nitrosonornicotine (NNN) causes tumors of the esophagus and nasal cavity in rats, lung in mice, and respiratory tract in hamsters. Although the manufacturing of cigarettes is an important domain of Moldovan industry, there are no reports in the literature on TSNA analysis in Moldovan tobacco. The main purpose of the present study was an initial evaluation of TSNA levels in Moldovan cigarette tobacco. Eighteen brands of Moldovan cigarettes, representing 78% of all brands produced in Moldova, were analyzed. Four TSNA-NNN, NNK, N'-nitrosoanatabine (NAT), and N'-nitrosoanabasine (NAB)-were analyzed by gas chromatography with nitrosamine selective detection (GC-TEA). Levels of TSNA in most Moldovan cigarettes were substantially lower than in American brands. Mean levels of NNN in three commercial American brands were 3.32 +/- 0.88 (SD) microg/g as compared to 0.579 +/- 0.548 microg/g, range 0.093-2.09 microg/g (N = 18), in the cigarettes produced in Moldova. For NNK and NAT, mean levels in the American brands were 1.57 +/- 0.178 and 1.99 +/- 0.579 microg/g, respectively, while the corresponding values for Moldovan cigarettes were 0.193 +/- 0.089, range 0.104-0.484 microg/g, and 0.160 +/- 0.114 microg/g, range 0.055-0.481 microg/g. The highest levels of NNN-1.10-2.09 microg/g-were observed in "American type" cigarettes manufactured from high-quality tobacco. The results of this study should be useful in heightening the awareness of the dangers of smoking in Moldova and can be envisioned as the initial step in the control of tobacco-related cancer in this republic.
Kits designed to detect ochratoxin A (OA) and T-2 toxin by a membrane-based flow-through enzyme immunoassay were studied collaboratively by screening cereals (wheat, rye, maize and barley) for the presence of these mycotoxins. Sample preparation and test procedure were clearly described in the instruction leaflets included in the kits. A simple methanol-based extraction followed by filtration and dilution steps was prescribed. Reagents were successively pipetted to the membrane of the device, then colour development was evaluated visually. Limits of detection for the ochratoxin A and T-2 toxin tests were 4 and 50 microg kg(-1), respectively. Five laboratories took part in the first stage of this study, and five more joined the second stage. Cereal samples (blank, spiked or inoculated) were shipped with the kits to the participating laboratories, while results obtained were confirmed by high-performance liquid chromatography with fluorescence detection and by gas chromatography-mass spectrometry for ochratoxin A and T-2 toxin, respectively. Some initial difficulties were encountered. In the second stage, four ochratoxin A and four T-2 toxin kits were used by 10 collaborators to analyse 21 cereal samples. For the ochratoxin A kits, the percentage of false positive and false negative results were 2% and 4%, respectively. The results of one T-2 toxin kit were outliers and when excluded, the overall percentage false positive and false negative results were 6% and 3%, respectively.