Formaldehyde, radioactive

Thermosetting Reactive Polymers. Materials used as thermosetting polymers include reactive monomers such as urea—formaldehyde, phenoHcs, polyesters, epoxides, and vinyls, which form a polymerized material when mixed with a catalyst. The treated waste forms a sponge-like material which traps the soHd particles, but not the Hquid fraction the waste must usually be dried and placed in containers for disposal. Because the urea—formaldehyde catalysts are strongly acidic, urea-based materials are generally not suitable for metals that can leach in the untrapped Hquid fractions. Thermosetting processes have greater utiHty for radioactive materials and acid wastes. 

The methylation of secondary amines works better than for primary amines because there is no competition between the formation of mono- or dimethylated products. The best results for the microwave-enhanced conditions were obtained when the molar ratios of substrate/formaldehyde/formic acid were 1 1 1, so that the amount of radioactive waste produced is minimal. The reaction can be carried out in neat form if the substrate is reasonably miscible with formic acid/aldehyde or in DM SO solution if not. Again the reaction is rapid - it is complete within 2 min at 120 W microwave irradiation compared to longer than 4 h under reflux. The reaction mechanism and source of label is ascertained by alternatively labeling the formaldehyde and formic acid with deuterium. The results indicate that formaldehyde contri-... 

Recently, the enzymatic formation of folinic acid has been utilized to synthesize radioactively labeled products.34 The preparation of 5-formyl tetrahydrofolate, 9,3, 5 -3H and 5-formyl-14C-tetrahydrofolate starts with tritiated folic acid, which is reduced to dihydrofolate, incubated in the presence of formaldehyde, dihydrofolate reductase, and NADPH, and finally incubated with 5,10-methylenetetrahydrofolate dihydrogenase. The product,... 

Formaldehyde or glutaraldehyde followed by buffer wash and postfixation in 0S04 and dehydration [3H]-Leucine Proteins and polypeptides, although investigators did not rigorously establish chemical form of radioactivity compared results to those obtained by TCA precipitation Formahn— all but 14.5% Glutaraldehyde —all but 3.5% Vanha-Pertulla and Grimley (22)... 

Formaldehyde or glutaraldehyde Labeled mannose Polysaccharide Considerable 20% loss of radioactivity with either fixative Vanha-Pertulla and Grimley (22)... 

Exothermic chemical reactions, 25 299-301 catalytic converter, 10 45 formaldehyde manufacture by, 12 115 temperature-dependent enthalpy changes for, 25 303-305 Exothermic polymerization, 10 709 Exotic radioactive decays, 21 305-306 Expandable polystyrene (EPS),... 

Compared with radioactive ISH, nonradioactive ISH requires a 10- to 50-fold higher concentration of probes such as oligonucleotides. However, signal amplification is decreased by increasing probe concentration. Therefore, since nonradioactive probes have limited sensitivity, especially when applied to low-abundance mRNAs, a technique is required for signal amplification. One such technique consists of an optimized protocol for rapid signal amplification based on catalyzed reporter deposition (CARD) that increases the sensitivity of nonradioactive mRNA ISH on the formaldehyde-fixed and paraffin-embedded tissues (Speel et al., 1998). This technique facilitates the detection of low-copy mRNAs by ISH (Yang et al., 1999). 

Production equipment that cannot be sterilized must be sanitized and disinfected by an appropriate method. This can be done by use of biocides like alcohols (70%), hydrogen peroxide, or formaldehyde-based chemicals or a combination of these. These can either be used for surface disinfections by wiping or spraying or even better by use of gas or dry fog systems for application of the disinfectants. The effect of cleaning and sanitation should be monitored. Microbiological media contact plates can be used to test critical surfaces, as inside the hot cells or glove boxes. The test samples must then be handled and monitored as radioactive contaminated units. 

This reaction was carried out with labeled isobutylene (l- C-2-methyl-l-propene, (CH3)2C-= CH2), and the methallyl chloride contained was collected, purihed, and subjected to ozonolysis. Formaldehyde (H2C—O) and chloroacetone (CICH2COCH3) were obtained all (97% or more) of the radioactivity was present in the chloroacetone. 

Similarly, (+ )-reticuline (XCVII) labeled both in the 6-methoxyl group (5.9%) and in its X-methyl group (94%) when fed to H. canadensis gave radioactive berberine 126). Location of the labels at the expected positions was established by acid hydrolysis to formaldehyde (5.6%) and by conversion to benzoic acid (91 %), as described above, and is illustrated in Chart VI. 

Heck et al. (1985) also determined the fate of inhaled formaldehyde in the rat. Male Fischer 344 rats were placed in a nose-only inhalation chamber and exposed to a 14.412.4 ppm air concentration of formaldehyde for 2 hours, were sacrificed, and a venous blood sample was collected and analyzed for formaldehyde content. Unexposed control rats had a mean formaldehyde blood level of 2.24 0.07 g/g of blood. Rats exposed to the 14.4 ppm air concentration of formaldehyde had blood concentrations of 2.25 0.07 g/g. These results indicate that during a nose-only inhalation exposure of rats to this concentration of formaldehyde, no significant quantities of formaldehyde could be detected in the blood. Lack of increase in blood formaldehyde levels indicates that only local absorption took place and absorbed formaldehyde was metabolized before reaching the bloodstream. In a similar study by Heck et al. (1983), Fischer 344 rats were exposed by inhalation to " C-formaldehyde at 8 ppm for 6 hours. Concentrations of total radioactivity (most likely as " C-formate) in the w hole blood and plasma were monitored for an additional 8 days. Plasma concentrations of " C increased over the exposure period, reaching a maximum at the termination of exposure. Plasma " C concentrations then declined slowly over the next few days. 

No studies w ere located that described the distribution of formaldehyde or its metabolites in humans after inhalation exposure. Several studies are available that describe the distribution of formaldehyde in laboratory animals. Heck et al. (1983) examined the fate of C-formaldchydc in Fischer 344 rats. Rats w ere exposed by inhalation to C-formaldehyde at 8 ppm for 6 hours. Concentrations of total radioactivity in the w hole blood and plasma were monitored for 8 days. The terminal half-life of the C w as approximately 55 hours, w hich was considerably longer than the known half-life of formaldehyde (about 1.5 minutes in monkeys), indicating both the metabolism of C-CHjO to other molecules (i.e., fonnate) and incorporation into other molecules. Radioactivity in the packed blood cell fraction was multiphasic it initially increased during exposure, declined during the first hour postexposure, then began to increase again, reaching a maximum at approximately 35 hours postexposure. The terminal phase of the packed red blood cell fraction had a very slow decline in radioactivity, which would likely continue for several weeks after exposure ended (half-life >55 hours). 

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