Meeting Briefs from Dallas
Aeration of medical plastics Medical plastics that are sterilized with ethylene oxide must be aerated to remove residual traces of the oxide and its reaction products (l&EC). Dr. Richard W. Tock of the University of Iowa's chemical engineering department says that unless this is done, chemical burns in body tissues will result. Ethylene oxide is commonly used to sterilize plastic tubing and other materials nonthermally. It has a "devastating effect" on human tissue and reacts with polyvinylidene chloride (often used for surgical tubing) to form chlorohydrin, a highly toxic material. The problem can be solved by aerating the materials between sterilization and use. Polyurethanes as surgical adhesives Rapid-setting polyurethane plastics can be modified to produce surgical adhesives (Organic Coatings and Plastics). Dr. Paul Y. Wang of the University of Toronto's institute of biomedical electronics and engineering reports that some preparations set in 15 seconds and could be used to control bleeding in some cases. Adhesion of soft polymers to soft organs such as the liver and spleen with strength superior to the tissues themselves has also been obtained with modified silicone and neoprene polymers. Still in the first stages of experimentation, the new polymers are better for this use than substituted cyanoacrylates, which have been evaluated for many years and more or less rejected. Flame retardant for polyester fabrics Amoco Chemicals has introduced a developmental flame retardant, 2,5-dibromoterephthalic acid, for fabrics made from polyester fibers (Cellulose). The retardant is now being tested by several polyester makers. Amoco's Dr. James P. Nelson says that, unlike some retardants, the dibromo version developed by Amoco is chemically bonded to the fiber and will not wash off or cause dermatitis. Flammability of polyesters treated with the retardant is quite low, especially when antimony is used to enhance the effect of the bromine. Polyester samples treated with the retardant and containing 4% antimony are consistently selfextinguishing when subjected to the flame of a Bunsen burner. PCB's from pesticides DDT and DDE can change into persistent PCB's in simulated sunlight (Pesticide). Kenneth W. Moilanen of the University of California, Davis, says that this offers a possible explanation for the worldwide distribution of PCB's, although the effect has only been observed in the laboratory. Since DDT spends up to four years in the atmosphere after application, there is ample time for degradation by the ultraviolet radiation from sunlight. The particular PCB found in the laboratory study to result from DDT degradation is 4,4'-dichlorobenzophenone. Irradiated DDE vapor produces two other PCB's—tri- and tetrachlorinated PCB's. Antibiotic may promote cancer spread The antibiotic rifampicin, used to treat tuberculosis, promotes the spread and growth of certain cancers in mice, finds Dr. David R. Grassetti of Arequipa Foundation Laboratories, Berkeley, Calif. (Medicinal). This study on animals, Dr. Grassetti says, indicates that TB patients receiving this antibiotic face the possibility, if they also have cancer, of having that cancer spread. Many drugs used in cancer therapy have immunosuppressive side effects. One of these side effects, that Dr. Grassetti says is not widely recognized, is that the drugs favor the formation of metastases. To make matters worse, recent reports have indicated the disturbing fact that surgery alone can cause the accelerated formation of metastases postoperatively.
Fetal cell analysis for genetic disease Ultramicro methods capable of analyzing single fetal cells for the early detection of genetic disease have been developed by Dr. M. L. Moss of Oak Ridge National Laboratory's analytical chemistry division and molecular anatomy program (Analytical). Prenatal testing at an early stage of pregnancy may become possible in the future because only V1000 of the amniotic fluid presently used in diagnosis is required by the new technique. The tests are performed entirely under a microscope with glassware manipulated by pneumatic controls. Emphasis in the work at Oak Ridge is now directed toward refinement of the new techniques for thorough clinical evaluation. Trace metals help fluorides fight tooth decay Trace metals in drinking water form a chemical complex with natural or added fluorides which is more effective in fighting tooth decay than is the fluoride alone (Water, Air, and Waste). These complexes, particularly those with iron and aluminum, also impart increased resistance to the acid produced by oral bacteria, the source of tooth decay. Dr. Nabih Kelada, of the University of Michigan's school of public health, says that up to one third of the fluoride in drinking water in some localities is actually present in the metal-complex form. The findings are expected to influence the treatment of water in municipal systems in the future. Removal of the trace metals may reduce the effectiveness of the fluorides now added to fight tooth decay. Base-metal catalyst from UOP A base-metal catalyst offering the potential of meeting the 1975 emission standards for automobiles over 50,000 miles has been disclosed by Universal Oil Products (l&EC). Dr. Richard K. Lee says that by operating the copper-chromium-alumina catalyst above 650° C. formation of sulfate deposits can be circumvented. These deposits had been a problem with previous attempts to use the catalysts. Concern over the availability of noble metals led UOP researchers to develop the base-metal catalysts. Dr. Lee says that noble metals are not directly affected by sulfur combustion in catalytic converters, but deactivation of supported noble metal catalysts may occur if constituents of the substrate form stable sulfates. Method measures sulfuric acid in air A convenient, cheap, and reliable way to measure the amount of sulfuric acid in the air has been developed at Louisiana State University (Water, Air, and Waste). At an equipment cost of less than $200, the sensitivity obtained by the new device is at least a hundred times greater than earlier methods. In operation, the method collects acidic pollutants on filter tapes which are then transferred to a ring oven for analysis. The analysis involves the production of bromine in proportion to the amount of pollutants collected. The bromine is reacted with fluorescein dye to produce a colored material. The amount of colored material is the measure of acidic material in the sample. Laser-induced fluorescence Laser-induced fluorescence, using an organic dye laser as a molecular beam detector, is destined to change the way chemists search for the presence of trace species, says Dr. Richard N. Zare of Columbia University (Physical Chemistry). The technique permits extremely sensitive and rapid detection of quantities as small as an attogram (10~ 18 gram). Although the technique is now of primary interest to chemists in solving problems in reaction dynamics, Dr. Zare believes it is applicable to such practical problems as pollution monitoring and rapid clinical analyses. April 23, 1973 C&EN 21
