Diphenyl-dimethyl-polysiloxane

Diphenyl/dimethyl polysiloxane colmnns (e.g., VOCOL, Rtx-Volatiles, HP-VOC, Rtx-502.2) were the first columns used to analyze VOCs. Although these are low bleeding phases and oxidation resistant, their main drawback is the incomplete resolution of very volatile compounds (such as bromomethane and chloroethane). 

The polarity of the solute is crucial for the choice of stationary compound, which in an optimal case would have a similar polarity than the solute. Common stationary phases in open tubular columns are cyanopropylphenyl dimethyl polysiloxane, carbowax polyethyleneglycol, biscyanopropyl cyanopropylphenyl polysiloxane and diphenyl dimethyl polysiloxane. For packed columns there are more options available. 

GC column 5% Diphenyl-95% dimethyl polysiloxane-fused silica capillary (30m x 0.25 mm i.d. 0.25-pm film thickness)... 

In spite of the considerable instrumental advances made, the detection of all the constituents of an essential oil is an extremely difficult task. For example, GC chromatograms relative to complex mixtures are characterized frequently by several overlapping compounds Well-known examples are octanal and a-phellandrene, as well as limonene and 1,8-cineol, on 5% diphenyl-95% dimethyl-polysiloxane stationary phases, while unsufficient resolution is observed between citronellol and nerol or geraniol and linalyl acetate. On the other hand, the overlapping of monoterpene alcohols... 

GC column A capillary column of intermediate polarity can give adequate resolution of isomers as well as unsaturated compounds. Many such columns are commercially available. These include 105 m long x 0.53 mm ID, Rtx-502.2 60 m long x 0.75 mm ID, VOCOL 60 m long x 0.53 mm ID, DB-62 or equivalent. Other capillary columns include 95% dimethyl-5% diphenyl polysiloxane coated columns, such as DB-5, SPB-5, Rtx-5, AT-5, or equivalent. These columns are also suitable for separation of a number of nonhalogenated organic compounds of intermediate polarity. 

Analyze the hexane solution as directed under Gas Chromatography, Appendix HA, with the following conditions Use a gas chromatograph equipped with a flame-ionization detector and a 30-m x 0.32-mm (id) column with a stationary phase consisting of 0.25-pm, cross-bonded, 95% dimethyl 5% diphenyl polysiloxane (JBW Scientific DB-5.625, or equivalent). Set the injector to 280°, and hold the temperature at 70° for 4 min, and then increase it to 250° at intervals of 10° per min. Use nitrogen gas as a carrier with a flow rate of 70 mL per minute. The detection is FID at 280°. 

The numbers correspond to those labeled on the chromatograms in Fig. 5. The ascending order of the congeners corresponds to the order of elusion from a 95 % dimethyl -5 % diphenyl-polysiloxane GC column (Sect. 5.1). Details of synthesis procedures are described elsewhere [92, 97,100], Chiral MeSOrCBs are marked with an asterisk. 

Gas chromatography was equipped with a DB-5, 95% dimethyl 5% diphenyl polysiloxane—bounded capillary column. It was combined with a mass spectrometer (ITS 40 Finnigan Matt). 

Polysiloxane and PolysiloxanelPMMA Copolymer Fractionation 249 Table 9.19 Reaction/Extraction Results with Poly(dimethyl)-co-(diphenyl)siloxane... 

Aminopropylmethylsiloxane/dimethylsiloxane copolymer Siloxanes and silicones, dimethyl-. See Dimethylsiloxane Siloxanes and silicones, dimethyl, diphenyl. See Phenylmethyl polysiloxane... 

GC-MS Analysis. The dimethylated anacardic acids were analyzed by gas chromatography-mass spectrometry (gc-ms). All analyses were performed in the El mode, using a Kratos model MS-25 mass spectrometer, with a 30m x 0.53mm RTX-5 (Restek Corp., cross bonded 95% dimethyl-5% diphenyl polysiloxane) capillary column with a temperature program of 250-280°C at 5°C/minute. 

Dimethyidiphenyl siloxanes and silicones. See Phenylmethyl polysiloxane Dimethyl diphenyl thiuram disulfide CAS 10591-84-1... 

Finally, melting point depression measurements have been conducted on several symmetrically substituted polysiloxanes, specifically the dimethyl, diethyl, di-n-propyl, and diphenyl polymers. Interpretation of such experimental results yields entropies of fusion. Although it is difib-cult to extract a reliable configurational entropy from this quantity, such results could help elucidate the configurational characteristics of the chains thus investigated. ... 

Silicone PSAs are blends or reaction products of the combination of a poly-organosiloxane, such as poly(dimethyl siloxane) or its copolymers with diphenyl-siloxane or methylphenyl siloxane, with a polysiloxane resin, which is largely inorganic. Pendant vinyl groups may also be incorporated into silicone PSAs,... 

High-resolution gas chromatography (HRGC) has been widely applied for the determination of PCB contents in water samples [112]. PCBs can be separated on a 30-50 m fused silica capillary column with various chemically bonded stationary phases. Table 20.6 shows combinations of column lengths, stationary phases, oven temperature programs, and detectors. Polysiloxane (95% dimethyl-5% phenyl) is the most widely used stationary phase, although 5% diphenyl polydimethylsiloxane, 7% methyl-7% cyanopropyl-phenyl polysiloxane, 95% dimethyl 5% phenyl polysiloxane, 50% phenyl-methyl-polysiloxane are also used. 

---