A 50% n-octylmethyl, 50% diphenyl-polysiloxane as stationary phase with unique selectivity for gas chromatography

Abstract

An n-octylmethyl, diphenyl-polysiloxane called SOP-50-Octyl was prepared by a condensation reaction of bis(dimethylamino) n-octylmethylsilane with diphenylsilanediol. The resulting copolymer was a gum with high molecular weight and was obtained with a yield of 80%. 1H and 29Si NMR spectroscopy revealed that the copolymer was a 52% octylmethyl, 48% diphenyl-polysiloxane with random microstructure. Small cyclic impurities could be almost quantitatively removed via a purification step. SOP-50-Octyl was used as stationary phase for the preparation of wall coated open tubular fused silica capillary columns for gas-liquid chromatography. The capillary columns exhibited high separation efficiency and high inertness. The stationary phase offered a unique selectivity due to its unique composition. The Rohrschneider-McReynolds constants indicated a low overall polarity in spite of the high phenyl content, as the polarity was distinctly decreased by the octyl substituent. Furthermore, the octyl substituent was responsible for a high column bleed, reducing the maximum allowable operating temperature to 280 degrees C. The elution temperatures of apolar compounds were increased due to increased interaction of the octyl substituent with the analytes. Some applications with volatile and semi-volatile organic compounds illustrate that SOP-50-Octyl is an excellent choice for confirmational analyses.

A 3,4-2(trifluoromethyl phenyl)-2,5-diphenyl phenyl grafted polysiloxane as a stationary phase for gas chromatography

“…22,23 Table 2 lists the Rohrschneider-McReynolds constants and the overall polarity on four different columns. 11,22 This CP-index indicates that DFP-15 has a polarity similar to the OV-17 column (50% dimethyl, 50% diphenyl-polysiloxane) exhibiting a CP-index at 20.5, while the overall polarity of DFP-8 is similar to 24% diphenyl, 76% dimethylpolysiloxane. 11,18 Therefore, increasing the content of the 3,4-2(triuoromethyl phenyl group)-2,5-diphenyl phenyl group has a signicant effect on the overall polarity and on the individual interactions.…”

“…22,23 This CP-index indicates that DFP-15 has a polarity similar to the OV-17 column (50% dimethyl, 50% diphenyl-polysiloxane) exhibiting a CP-index at 20.5, while the overall polarity of DFP-8 is similar to 24% diphenyl, 76% dimethylpolysiloxane. 11,18 Therefore, increasing the content of the 3,4-2(triuoromethyl phenyl group)-2,5-diphenyl phenyl group has a signicant effect on the overall polarity and on the individual interactions. Additionally, each Rohrschneider-McReynolds constant interacts with the stationary phase in a particular way: X 0 (benzene)-dispersive interactions; Y 0 (1-butanol)-proton donor and acceptor capabilities plus dipolar interactions; Z 0 (2-pentanone)-dipolar interactions plus weak proton acceptor but no proton donor capabilities; U 0 (1-nitropropane)-dipolar interactions; and S 0 (pyridine)-strong proton acceptor capabilities.…”

“…Thus, Mayer and his group synthesized 75% diphenyl, 25% dimethylpolysiloxane to serve as the high-temperature stationary phase, where the column temperature could reach 400 C. 6 Later, they prepared 50% n-octyl methyl, 50% diphenyl polysiloxane; this stationary phase had special selectivity and excellent performance with low polarity. 11 Generally, the separation properties of the stationary phase are improved if a single phenyl substituent group is replaced by a high concentration of benzene rings. Furthermore, increasing the rings of the polycyclic aromatic hydrocarbons (PAHs) connected by single bonds and improving the molecular weight and viscosity of the polymer will improve its polarity, selectivity, lm-forming properties and high-and-low temperature resistant properties.…”

Synthesis and characterization of diphenyl–phenyl polysiloxane as a high-temperature gas chromatography stationary phase

“…However, these modied stationary phases synthesized by Lee et al could only be used at temperatures below 280 C. Remarkable improvement was recently achieved by Mayer et al, who have synthesized polysiloxane composed of 75% diphenyl and 25% dimethyl (SOP-75); moreover, they used the polysiloxane to coat fused silica capillary columns for use in hightemperature GC analyses. 11 This stationary phase offered specic selectivity and thermal stability at temperatures of up to 400 C. 11 Similarly, more recently, modied polysiloxanes containing 50% n-octylmethyl, 50% diphenyl (SOP-50-Octyl) 12 and triuoropropyl 13 have been utilized as GC stationary phases. These two types of stationary phases exhibited unique selectivity and could be used at high operating temperature ranges.…”

Ionic liquid‐bonded polysiloxane as stationary phase for capillary gas chromatography

“…It is well known that functionalized polysiloxanes have been extensively used as stationary phases for GC due to its thermal stability and good film‐forming ability 13. Functionalized polysiloxanes, such as methyl, phenyl, cyanopropyl, or trifluoropropyl polysiloxanes 14–18 have been recognized as the most popular stationary phases with particular selectivity. Additionally, some host molecules, including crown ether, cyclodextrin, calixarene and fullerene, had also been successfully bonded into the main chains of polysiloxanes as functional groups to improve the selectivity of the stationary phases 19–24.…”