Methyl silicones

The most widely used method of analysis for methylene chloride is gas chromatography. A capillary column medium that does a very good job in separating most chlorinated hydrocarbons is methyl silicone or methyl (5% phenyl) silicone. The detector of choice is a flame ionization detector. Typical molar response factors for the chlorinated methanes ate methyl chloride, 2.05 methylene chloride, 2.2 chloroform, 2.8 and carbon tetrachloride, 3.1, where methane is defined as having a molar response factor of 2.00. Most two-carbon chlorinated hydrocarbons have a molar response factor of about 1.0 on the same basis. 

Figure 12.22 SFC-GC analysis of aromatic fraction of a gasoline fuel, (a) SFC trace (b) GC ttace of the aromatic cut. SFC conditions four columns (4.6 mm i.d.) in series (silica, silver-loaded silica, cation-exchange silica, amino-silica) 50 °C 2850 psi CO2 mobile phase at 2.5 niL/min FID detection. GC conditions methyl silicone column (50 m X 0.2 mm i.d.) injector split ratio, 80 1 injector temperature, 250 °C earner gas helium temperature programmed, — 50 °C (8 min) to 320 °C at a rate of 5 °C/min FID detection. Reprinted from Journal of Liquid Chromatography, 5, P. A. Peaden and M. L. Lee, Supercritical fluid chromatography methods and principles , pp. 179-221, 1987, by courtesy of Marcel Dekker Inc.

Silicone Good Phenyl-methyl silicones are more stable than are methyl silicones. Platinum cure is superior to peroxide cure full cure during manufacturing can eliminate most postirradiation effects. 

The use of a fused silica capillary column for the GC analysis of the neutral oil extract has provided the means for improving the resolution of components in a more inert system. The sultones are determined by temperature-programmed GC over CP-Sil-5 CB (methyl silicone fluid) in a 25 m x 0.2 mm fused silica capillary column using nonadecane as internal standard. A sample split ratio of 1 100 is recommended for a 3-pl injection. 

Chromatography Hewlett-Packard Ultra2 (25 m x 0.33 mm) cross-linked phenyl methyl silicone fused silica capillary column. Temperature program 55° (1 min.) -I- 30°C/min. to 180°C, and 4°C/min. to 320°C. 

Chlorinated aromatic hydrocarbons Volatile methyl-silicon compounds Methylcyclopentadienyl manganese (CO)3... 

Tuazon EC, SM Aschmann, R Atkinson (2000) Atmospheric degradation of volatile methyl-silicon compounds. Environ Sci Technol 34 1970-1976. 

The products of the oxidation reaction were analysed by gas chromatography (Hewlett Packard, 5880 A), employing a FID detector and equipped with a capillary column (50 m x 0.25 mm crosslinked methyl silicone gum). The reactants and products of n-hexane oxidation were analysed by gas chromatography (Hewlett Packard, 5890) equipped with a FFAP column (30 m X 0.25 mm). The identity of the products was further confined by GC-MS (Shimadzu QCMC-QP 2000A). 

Oxyfluorfen column, fused-silica capillary column coated with cross-linked methyl silicone (25 m x 0.3-mm i.d., 0.52- am film thickness) temperature, column 200 °C (1 min), 10°Cmin to 250 °C (5 min), inlet and detector 250 and 300 °C, respectively gas flow rates, N2 carrier gas 30mLmin , N2 makeup gas 30mLmin H2 3.5mLmin" air llOmLmin injection volume, 2 p.L. ... 

Chlornitrofen and nitrofen conditions for GC/MS column, cross-linked methyl silicone capillary (12 m x 0.22-mm i.d., 0.33- am film thickness) column temperature, 60 °C (1 min), 18 °C min to 265 °C inlet, transfer line and ion source temperature, 260, 200 and 200 °C, respectively He gas column head pressure, 7.5 psi injection method, splitless mode solvent delay, 3 min electron ionization voltage, 70 eV scan rate, 0.62 s per scan cycle scanned mass range, m/z 100-400. The retention times for chlornitrofen and nitrofen were 11.8 and 11.3 min, respectively. The main ions of the mass spectrum of chlornitrofen were at m/z 317, 319 and 236. Nitrofen presented a fragmentation pattern with the main ions at m/z 283, 202 and 285. ... 

Product analysis Reaction mixtures were analyzed by GC using a crosslinked 5% phenyl methyl silicone (HP5, 30 m) or a nonbonded, poly(80% biscyanopropyl/20% cyanopropylphenyl siloxane SP2330, 60 m) capillary colunm. Reaction products were identified through their MS (HP 5971 series) and H NMR spectra (Bruker 300... 

The extracted fractions were esterified with either BF3-MeOH reagent or diazomethane and analyzed by GLC. Gas liquid chromatography (GLC) was conducted with a Perkin-Elmer Sigma 3 equipped with flame ionization detector. Separations were obtained on a Hewlett Packard 12 m x 0.2 mm i.d. capillary column coated with methyl silicon fluid (OV-101). The temperature was maintained at 80°C for 2 min then programmed from 80 to 220°C at 8°C/min. The injector temperature was 250°C. Mass spectra were obtained on a Hewlett Packard model 5995 GC-MS mass spectrometer, equipped with a 15 m fused silica capillary column coated with 5% phenyl methyl silicone fluid. Spectra were obtained for major peaks in the sample and compared with a library of spectra of authentic compounds. 

Analogous behavior was followed by the phenyl-substituted silene 156. The initially formed silene 157 underwent 1,3-methyl migration to give the silene 158, which then dimerized in a head-to-tail manner to yield three different stereoisomeric dimers 159, two of which were characterized by crystal structures. Again, the exchange of trimethylsilyl and trimethylsi-loxy groups at the ends of the Si=C bond occurred, followed by 1,3-methyl silicon-to-silicon rearrangements. The steps are summarized in Eq. (54). 

The third technique we used was a measurement of changes in the sorption behavior of a compound in the presence of humic materials. A thin film of OV-1, a methyl silicone gum used as a chromatographic stationary phase, was plated on the bottom of a 60 ml Hypo-Vial (Pierce Chemical Co., Rockford, 11.). A solution of radiolabeled pollutant was added to the vial in either buffered distilled water in a solution of humic materials. Again, it is assumed that the pollutant is solution consists of two fraction free and bound. It is also assumed... 

The chromatographic procedure may be carried out using a glass column (1.5 m x 2 mm) packed with acid-washed, silanized diatomaceous support (80-100 mesh) coated with 3% (w/w) of phenyl methyl silicone fluid (50% phenyl) (OV-17 is suitable) and maintained at 270 °C. 

Abbreviation for phenyl methyl silicone. Pneumatic Tyre... 

Abbreviation for phenyl vinyl methyl silicone. Pyrometer... 

Polymers which just contain the above repeat unit are termed methyl silicones, and are given the ISO designation MQ. 

It is possible to replace a few of the methyl groups (<0.5%) with a vinyl group, and the resultant vinyl methyl silicones (ISO designation VMQ) exhibit improved vulcanisation characteristics and... 

FIGURE 9.2 Gas chromatograms of an FT product, original and precolumn hydrogenated. Ampoule samples taken from the gaseous product flow at ca. 200°C. GC conditions Capillary, 100 m dr 0.25 mm df, 0.5 pm methyl silicone cross-linked temperature programm -80 to 270°C carrier gas H2 introducing gas N2 FID. 

The CGC analysis of the volatile degradation products were performed using a Perkin-Elmer Sigma 2000 capillary gas chromatograph. The column used was either a fused silica 0.25 micron, bonded methyl silicone (10 m, 0.25 mm I.D.) or a methyl/5% phenyl silicone (15 m 0.25 mm I.D.) bonded phase. The carrier gas was helium and the capillary column head pressure was maintained at 20 psi. The make-up gas for the pulsed electron capture detector (ECD) was 95% Ar/5% methane supplied at a flow rate of 60 ml/min. 

GC-GC-FTIR is similar to the one described previously except that the separated components are fed into an FTIR cell for identification. To effect a more complete separation of components, two different GC columns are used for instance, a 5% phenyl/phenyl-methyl silicone column might be followed by a 50% phenyl/phenyl-methyl silicone column [12],... 

EGSS-Y Copolymer of EGS with a higher proportion of methyl silicone than EGSS-X... 

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