Level Of Monomer Research Articles

The level of residual monomer in acrylic denture base materials with particular reference to a modified method of analysis

The level of residual monomer in acrylic denture base materials with particular reference to a modified method of analysis

Adequate Anticoagulation During Cardiopulmonary Bypass Determined by Activated Clotting Time and the Appearance of Fibrin Monomer

The adequacy of anticoagulation during 2 hours of cardiopulmonary bypass at 30° in 9 rhesus monkeys was determined by measuring the whole-blood activated clotting time (ACT) and by noting the appearance of thrombin-altered fibrin (fibrin monomer) and the relative consumption of clotting factors. Factors V and VIII, the heparin cofactor, antithrombin III, prothrombin time, partial thromboplastin time, ACT, platelets, hematocrit, fibrinogen, and fibrin monomer were determined prior to heparinization and after protamine. In 6 of 9 experiments, fibrin monomer became positive in the plasma during cardiopulmonary bypass (CPB), indicating that active coagulation was occurring. In 5 of the 6 animals, initial ACT was less than 400 seconds, and fibrin monomer appeared within the first 30 minutes of bypass. In 1 animal with an initial ACT of 439 seconds, fibrin monomer appeared after 60 minutes of bypass, at which time the ACT was less than 400 seconds. An abnormal level of fibrin monomer was not detected in 5 pediatric patients with an ACT greater than 450 seconds during CPB. Our experimental study and clinical data suggest that the lower limit, as measured by the ACT, for anticoagulant effect to provide coagulation-free CPB is at least 400 seconds.

Coatings update: Pollution and the paint industry

An interesting article by Brown [Journal of Paint Technology, 47, January (1975) p.69] describes the technical impact of government pollution regulations with particular emphasis on the coatings industry. In his article, he discusses vinyl chloride, pointing out that as of January 1, 1975, the maximum allowable level of vinyl chloride monomer is 1 p.pm. averaged over any eight‐hour period and not more than 5 p.p.m. averaged over any 15‐minute period.

Detection, Removal, and Effect of Unpolymerized Methylmethacrylate in Intraocular Lenses

Gas-liquid chromatography, infrared spectroscopy, or Raman spectroscopy were used to determine the level of monomer in intraocular lenses and in the preforms used in each step of the manufacturing process. Heating, lathing, molding, and grinding caused an increase in monomer content, presumably the result of depolymerization. The tendency of methylmethacrylate to volatilize, repolymerize, or dissolve precludes high monomer contents from persisting in intraocular lenses. Vacuum ovens or water baths significantly reduced the monomer content to levels of 0.5% or less. Lenses with a monomer content higher than that found in currently available commercial lenses had no effect on rabbit kidney cell cultures. Lens fragments with a similarly elevated monomer content were indistinguishable from lenses with a low monomer content in rabbit eyes. According to these data, monomer does not appear to be a toxic agent in currently available intraocular lenses.

Determination of vinyl chloride monomer by gas chromatography

A gas—liquied chromatographic method for trace amounts of vinyl chloride monomer, applicable to certain types of problems in the packaging of foods, is described. When an adequate sample can be dissolved in a suitable solvent and does not interfere, direct analysis of some materials is feasible. For other materials, food simulating solvents may be applicable. A level of vinyl chloride monomer as low as 5 ppb * can be determined in resins and plastic containers.

Quantitation of lactate dehydrogenase isoenzyme patterns of the developing human fetus

The differentiation of heart and liver lactate dehydrogenase isoenzymes during embryological development of the human was studied. At the end of 3 mth the percent level of heart monomer in heart and liver were identical. However with further development heart monomers decreased in liver and increased in the heart. The greatest rate of change occurred during the last trimester (7–9 mth) of development, whereby at this time patterns similar to those demonstrable in corresponding adult organs were evident. A similar study involving stillborns suggests the possibility that some of these cases might result from the lack of differentiation of LDH isoenzymes rich in heart monomer.