Suitable Clean-up Research Articles

Voids as a source of haze in weathered poly(2,2,4,4‐tetramethyl‐1,3‐cyclobutylene carbonate)

AbstractLong‐term weathering studies of the subject transparent thermoplastic polymer revealed that sheets extruded from pristine resine gradually became hazy. Electron microscopy of fracture surfaces showed that minute voids were created during outdoor exposure. By the application of the Mie light scattering theory, it was possible to calculate that the average void size was 4 × 103 Å and that the concentration of voids numbered about 106/mm3. Yet the total void volume of the poorest sample, which had a haze value of 26%, was less than 0.05%. The average void size decreased over a three‐year period, but the concentration increased with exposure. A mechanism of void formation was formulated based on photo‐induced moleculàr degradation. Chemical evidence suggests that molecular degradation occurs by complete unzippering of a molecule, resulting in the formation of carbon dioxide and 2,2,4‐trimethylpentene‐3‐al. The aldehyde is believed to plasticize the polymer in the vicinity of a growing void and the carbon dioxide acts as a blowing agent, therby generating a void. Simultaneously, free radicals formed during molecular decomposition initiate further degradation of neighboring molecules. The propensity of this resin to haze can be effectively overcome by suitable cleanup and stabilization procedures.

Gas Chromatographic Determination of Trace Amounts of the Insect Chemosterilants Tepa, Metepa, Methiotepa, Hempa, and Apholate and the Analysis of Tepa in Insect Tissue

Abstract A gas chromatographic method, sensitive to as little as 0.1 nanogram, was devised for analysis of the insect chemosterilants tepa, metepa, methiotepa, hempa, and apholate. The method is needed to monitor amounts and persistence of chemosterilant in treated insects. The procedure uses a flame-photometric detector. Response is linear (phosphorus analysis) between 0.1 and at least 200 ng. The procedure was shown to be directly applicable to analysis of methanol extracts of insects fed tepa. Concurrent gas chromatographic and radiometric analyses indicated that the radiometric method would not give satisfactory results without a suitable cleanup, whereas virtually no cleanup was required for the gas chromatographic analysis. The gas chromatographic method is rapid and easily carried out.

Determination of ethylene oxide based nonionic detergents in sewage.

AbstractA sensitive analytical method has been developed for the determination of ethylene oxide based nonionic detergents in sewage. After suitable cleanup procedures, which are described, the detergent is complexed with phosphotungstic acid in the presence of excess reagent. The excess reagent is then decomposed by raising the pH to 5 while the complex remains stable for a short period. The complex is separated from reagent decomposition products by partition between methyl ethyl ketone and dilute sodium chloride solution buffered to pH 5. Quantitative assay is made for tungsten since the amount of tungsten bears a stoichiometric relation to the ethylene oxide chain length.

Colorimetric Determination of Nemacide and Ronnel in Animal Tissues

Abstract colorimetric method is described for determining Nemacide® and ronnel in the body tissues of sheep and cattle. After extraction and suitable cleanup, the insecticide is hydrolyzed and the resulting 2,4-dichlorophenol or 2,4,5-trichlorophenol is steam distilled. The phenols are reacted with 4-aminoantipyrine; the colored compound is extracted into a nitromethanepyridine mixture and the absorbance determined at 490 mμ. Recoveries of 88-95% are possible when known amounts of Nemacide are added to the tissues. The method will detect residues as small as 0.05 ppm of Nemacide, and preliminary tests indicate that it is equally sensitive for the determination of ronnel.