The synthesis and characterization of a variety of mesomorphic (liquid-crystalline) side-chain polysiloxane (MEPSIL) solvents, said to be useful as gas chromatographic stationary phases, are described and discussed. The synthetic scheme is based upon the hydrosilatlon reaction that occurs when 4-(allyloxy)benzoyl esters are contacted with poly(methylslloxane) In the presence of a dicyclopentadlenylplatinum(II) catalyst, while product characterization Is carried out by IR, NMR, GC, DSC, elemental analysis, and direct-observation hot-stage light-polarized microscopy. Selectivity of the MEPSIL phases Is shown to differ very substantially from those exhibited by all other common GC solvents. The MEPSIL found overall to be the best suited as a GC stationary liquid exhibits a melting point of 139 °C (k -n) and a nematic/isotroplc (n -*-I) transition temperature of 319 °C, while the practical operating limits of the material span 150 to in excess of 300 °C.The development and optimization of chromatographic techniques for maximal resolution in minimal time of analysis, coupled with maximum sample throughput, continue to represent a substantial problem when dealing with analytes comprised of structurally related isomers. Among the most notably difficult of these are polycyclic aromatic hydrocarbons (PAH) which are, at the very least, ubiquitous environmental pollutants produced by the incomplete combustion of organic matter. Moreover, some of the most efficient carcinogens known at present are members of, or products derived directly
soon as the vapors of chloroform begin to form, the joint is separated to allow the air to escape. _ When the small droplets of chloroform appear near the glass joint, it is closed for the duration of the extraction. After 16 hours, the receiver and thimble are removed from the condenser and again placed in the drying oven. At the end of 5 hours they are removed and allowed to cool 15 minutes before being weighed. The weight of the extracted insect plus the weight of the extract is used as a•check on the original total weight of the insect.Large numbers of beet leafhoppers were collected from localities in south-central Idaho with especial reference to host plant and its condition. The insects were killed immediately with a minimum dose of cyanide and placed between sheets of crepe paper to dry. This method of collection lias been found to be the most satisfactory where samples must be transported over rough desert country. After their sex had been determined, the insects were dried (at 48°C ., 118.4°F .) for 24 hours, as this period had been found to give constant weight of the insect material.Table I shows a scries of determinations made from eight localities in southern Idaho in which four different host plants were involved-namely, flixweed (Sophia parviflora), sugar beet (Beta vulgaris), Russian thistle (Salsola pestifer), and sagebrush (Artemisio tridentata). Five females were used for each analysis reported. All percentages are based on the dry weight of the insect.
Literature Cited(1) Gorbach, G.. Mikrachemie, 12, 161 (1932).
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