Determination of surface hydroxyl concentration on glass and fused silica capillary columns

SummaryIn this study, the separation of polar compounds in solvating gas chromatography (SGC) was investigated. Capillary columns (250 gm i.d.) packed with deactivated siliceous particles, including SE-54 encapsulated silica particles, diol-bonded silica particles, and polyethylenimine (PEI) coated particles, and nonsiliceous particles of styrene-divinylbenzene were used. Polar compounds that were used as test solutes included ketones, aldehydes, esters, nitro-containing compounds, alcohols, phenols, fatty acids, and amines. It was found that capillary columns packed with SE-54 encapsulated particles were suitable for the separation of medium polar compounds, columns packed with diol bonded silica particles could be used for separation of strongly polar compounds such as fatty acids, and columns packed with PEI coated silica particles were suitable for the separation of basic compounds such as alkylamines under SGC conditions. Columns containing the polymeric particles could be used for the separation of medium polar compounds and weak bases, however, low column efficiency was observed. SGC was found to provide better separation of polar compounds than high pressure gas chromatography (HPGC). A sample of a peppermint oil was separated within 8 min under SGC conditions.

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“…However, for fused silica, the density of silanol groups is only approximately 0.2l OH nm -2, which is about 20 times smaller [24].…”

Section: Resultsmentioning

confidence: 99%

Separation of polar compounds by solvating gas chromatography with carbon dioxide mobile phase

Shen

Lee

1997

Chromatographia

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“…To model the equations, one requires an estimate of the number of sites available on the fused silica and the rates of adsorption/desorption. Since the adsorption of acridine on silica may be due to the hydroxyl groups present on the surface of deactivated silica, the number of hydroxyl sites on fused silica reported by Wright et al [31] was used as an initial guess of the total number of available sites for adsorption, S=3.49 x 10-Tmol.m -2, which corresponds to Ns of 6000 s -~. With the value of Ns at 60,000 s -~ (small value of the number of sites, S), the fractional coverage at any given time will be complete, say 0.99.…”

Section: Resultsmentioning

confidence: 99%

Influence of adsorption on the measurement of diffusion coefficients by Taylor dispersion

1996

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The effect of adsorption on the measurement of diffusion coefficients by the Taylor dispersion technique is investigated by modifying the governing equation to account for reversible, nonequilibrium adsorption. The resulting two-dimensional equations are solved by an explicit finite-difference technique. Experimental data for the acridine-carbon dioxide system indicated that acridine adsorbs on the walls on the tubing and these data were investigated with this model. The influence of various parameters including the number of sites and the rates of adsorption/desorption was investigated by conducting a parametric sensitivity analysis on the model. It was found that adsorption of the solute on the wall of the tubing could produce an error as high as 35% on the measured diffusion coefficient compared to the actual diffusion coefficient. Examination of the influence of each of the parameters will enable future investigators to reduce the effect of adsorption in the measurement of diffusion coefficients by Taylor dispersion.

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“…Borosilicate and soda-lime glass capillary columns can be leached with aqueous hydrochloric acid using the static [14 0, 170] or dynamic [171][172][173] method. In the static method the column is filled with 20% v/v hydrochloric acid, a small portion of the column emptied and then evacuated, the ends sealed and the column heated overnight at 140 to 170°C.…”

Section: Surface Modification Reactionsmentioning

confidence: 99%

The Column in Gas Chromatography

Poole

1991

Chromatography Today

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Determination of surface hydroxyl concentration on glass and fused silica capillary columns

Cited by 29 publications

References 6 publications

Separation of polar compounds by solvating gas chromatography with carbon dioxide mobile phase

Separation of polar compounds by solvating gas chromatography with carbon dioxide mobile phase

Influence of adsorption on the measurement of diffusion coefficients by Taylor dispersion

The Column in Gas Chromatography

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