Gas chromatography of homologous esters

Gas Chromatographic Characterization of Silica Bonded with a Phenylpolysiloxane Film

A method of synthesizing modified silica with a dense grafted phenylpolysiloxane layer is described. Gas chromatography at zero surface coverage has been used for investigating the adsorption properties of both modified and initial silicas. It was shown that the thermodynamic parameters for retention (retention volume, Va; heat, q; and entropy, ΔS0, of adsorption) and the Kovats retention indices I for different classes of organic compounds are essentially changed with surface modification. The increase in Va and q for n-alkanes on phenyl-bonded silica was interpreted as due to penetration of the solutes into the grafted phenylpolysiloxane layer. The significant reduction in retention parameters for all compounds capable of specific interaction, including the formation of hydrogen bonds, on the phenyl-bonded silica relative to the initial silica has allowed conclusions to be drawn regarding the weak role of residual silanol groups in the retention process. These conclusions have been confirmed by a comparison of the chromatographic properties of phenyl-bonded silica and the polymethylphenylsiloxanes OV-17 and OV-25.

Ketoimine modified silica as an adsorbent for gas chromatographic analysis of olefins

New adsorbents for capillary complexation GC have been proposed. The adsorbents contain free ketoimine groups which enable binding copper(II) and chromium(III) chlorides. The adsorbents obtained have been characterised by elemental analysis, differential scanning calorimetry and electron spin resonance. The specific interactions between the adsorbent and adsorbate molecules have been characterised by retention parameters (retention index - I, specific retention volume - Vg, molecular retention index - deltaMe). Attempts were also made at separating mixtures of olefins.

Fatty acids. VII. The gas-liquid chromatographic properties of all dimethylene interrupted methyl cis,cis-octadecadienoates

The gas-liquid chromatographic behaviour of all the dimethylene interrupted methyl cis,cis-octadecadienoates was studied on polar (Carbowax 20M, FFAP, DEGA, DEGS and Silar 10C), semi-polar (XE-60) and non-polar (SE-30, OV-101 and Apiezon L) stationary phases. The equivalent chain length of each isomer is recorded; the possibility of separation and the retention pattern of these isomers are discussed.