Determination of surface polarity by heterogeneous gas-solid chromatography

Boudreau, Scott P.; Cooper, William T.

doi:10.1021/ac00129a028

Cited by 26 publications

(13 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Adsorption of SDS and CTAB on C-l8 and cyanopropyl chemically derivitized silica was investigated using cross polarization/magic angle spinning 13 (CP/MAS 13 C NMR). All NMR experiments were performed at 50 MHz on a Bruker/IBM WP-200 S Y spectrometer equipped with an IBM solids control accessory and a Doty-type solid-state probe.…”

Section: Methodsmentioning

confidence: 99%

“…The dispersion pattern of the cyano group for the pure stationary phase material can be rationalized on the basis of chemical considerations. Cyano groups are known to interact with residual silanols [13]. The fact that some residual silanols will and some will not interact with cyano groups and to the varying degrees they do would be expected to yield a dispersion pattern.…”

Section: Berthod [11] Has Measured Adsoption Isotherms For Sds and Ctmentioning

confidence: 99%

See 1 more Smart Citation

Selectivity in Micellar Liquid Chromatography

Lavine

Hendayan

Cooper

et al. 1999

ACS Symposium Series

Self Cite

View full text Add to dashboard Cite

Micellar reversed phase liquid chromatography (RPLC) and solid state NMR have been used to study the interactions of two ionic surfactants with alkyl and cyanopropyl bonded phase columns. The two surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) are commonly used in micellar RPLC. Differences in selectivity between CTAB and SDS micellar RPLC on alkyl bonded phases can be attributed to the differing nature of the SDS-and CTAB-bonded phase association. For SDS, the association leads to the formation of an anionic hydrophilic surface layer, which would explain the superior resolution achieved by SDS micellar mobile phases for hydrophilic compounds on C-18. For CTAB, the association leads to a more hydrophobic bulk stationary phase, where the nitrogen head group is partially incorporated into the C-18 phase because of strong hydrophobic interactions between the C-18 bonded chains and the methyl nitrogens. The unusual behavior exhibited by cyano bonded phase columns towards ionogenic compounds in SDS and CTAB micellar RPLC can be attributed to strong interactions between the polar head group of the ionic surfactant and the cyano functionality of the polar bonded phase. Models depicting the structure of the surfactant modified C-18 and cyanopropyl bonded stationary phase are proposed from solid state NMR data, and these models are in good agreement with the selectivity exhibited by these bonded phase columns toward polar and ionogenic compounds in micellar RPLC. 290

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Berthod [11] Has Measured Adsoption Isotherms For Sds and Ctmentioning

confidence: 99%

Selectivity in Micellar Liquid Chromatography

Lavine

Hendayan

Cooper

et al. 1999

ACS Symposium Series

Self Cite

View full text Add to dashboard Cite

show abstract

“…Gas-solid chromatography is a suitable technique for studying changes in surface morphology and heterogeneity of solids, the shape of adsorption isotherms and the thermodynamics of adsorption at either zero or finite surface coverage [435][436][437][438][439][440]. Interpretation of the data is not as straightforward as for gasliquid partitioning since isotherms are frequently non-linear, even for the case of zero surface coverage, and the choice of a standard state for the adsorbate, that of a two dimensional gas, must follow an arbitrary convention.…”

Section: Gas-solid Chromatographymentioning

confidence: 99%

The Column in Gas Chromatography

Poole

1991

Chromatography Today

View full text Add to dashboard Cite

“…There has therefore been considerable effort devoted to understanding surface processes on silica-based materials. However, although most workers acknowledge the rich variety of surface adsorption sites on silica, there have been only a few attempts to describe thermodynamically its inherent surface heterogeneity (1)(2)(3)(4)(5). Because of variability in the chemical and physical state of the primary surface-active group (silanols), silicas, and particularly synthetically prepared silica gels, exhibit a wide range of surface adsorption energies.…”

Section: Introductionmentioning

confidence: 99%

“…We recently introduced a gas-solid chromatographic technique for measuring the surface polarity and surface selectivity of heterogeneous materials (5). The technique, which is based on the pioneering work of Rudzinski et al (1) and which we refer to as heterogeneous gas-solid chromatography (HGSC), can be used in most situations to determine the complete distribution of submonolayer adsorbate-adsorbent interaction energies from a single chromatogram.…”

Section: Introductionmentioning

confidence: 99%

Analysis of thermally and chemically modified silica gels by heterogeneous gas-solid chromatography and infrared spectroscopy

Boudreau¹,

Cooper²

1989

Anal. Chem.

View full text Add to dashboard Cite

The effects of thermal pretreatments at 180, 400, and 840 °C on the subsequent chemical modification of silica gel have been characterized by heterogeneous gas-solid chromatography (HGSC) and Infrared spectroscopy. Silica gel treated at 400 °C exhibited a surface area, surface polarity, and surface selectivity similar to those of the same material treated at 180 °C, even though the 400 °C gel could be modified to a much greater extent by gas-phase sllanization with hexamethyldlsllazane. The HGSC and IR results taken together Indicate that there are strongly hydrogen-bonded surface hydroxyl species on silica gel (sllanols or bound water), which are Inactive with regard to physical adsorption but which prevent complete stoichiometric modification of the silica surface. These Inactive sllanols can be removed with heating at elevated (>200 °C) temperatures, suggesting that thermal pretreatment of the silica support can be utilized to make more homogeneous and therefore more efficient bonded liquid chromatography stationary phases. Thermal treatment at 840 °C produces a silica gel with free (nonbound) Internal sllanols and external sllanols that can be completely modified with surface ligands, but the sintering that occurs at this temperature reduces the surface area of the silica gel such that It is no longer chromatographically useful.

show abstract

Determination of surface polarity by heterogeneous gas-solid chromatography

Abstract: A polarity scale for heterogeneous surfaces Is proposed that uses energy distribution functions calculated from chromatographic retention data. The energy required to form a complete monolayer (E^), obtained from the energy distribution

Cited by 26 publications

References 39 publications

Selectivity in Micellar Liquid Chromatography

Selectivity in Micellar Liquid Chromatography

The Column in Gas Chromatography

Analysis of thermally and chemically modified silica gels by heterogeneous gas-solid chromatography and infrared spectroscopy

Contact Info

Product

Resources

About