Behaviour of chemically bonded alkylmethyldichlorosilanes to silica gel in reversed-phase high-performance liquid chromatography

Hemetsberger, H.; Kellermann, Marlene; Ricken, H.

doi:10.1007/bf02263084

Cited by 87 publications

(14 citation statements)

References 21 publications

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“…This is in agreement with the work of KARCH et al 7) and independently with the work of HEMETSBERGER et al 8) Both groups were able to prepare excellent packings from SI 100 silica and methyloctadecyldichlorosilane. Fig.…”

Section: In-situ Columnssupporting

confidence: 91%

Custom made C18 columns for the hydrophobic chromatography of cephalosporin C derivatives.

White¹,

FOX²

1982

J. Antibiot.

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"Hydrophobic chromatography", which is a variation of reverse phase chromatography, is applicable to the analysis of cephalosporin C derivatives, especially in fermentation broths. Unfortunately, there are no commercial C18 columns which are entirely suitable for this class of compounds.For this reason C18 columns were prepared by an in-situ bonding technique and were optimally designed for cephalosporin C derivatives.Mono-, di-and trifunctional octadecyl bonding agents were used with 10 Ftm silica of both 60 A and 100 A pore diameter. The best results were obtained with the difunctional agent, methyloctadecyldichlorosilane, and 100 A silica. "Endcapping" of residual silanol groups with a trimethylsilylation agent was optional, since good results were obtained with both a plain C18 column and one that was "endcapped" ."Hydrophobic chromatography" is a variation of the reverse phase technique in which a neat (i .e., no organic component) aqueous solvent is used as the mobile phase. This mode of chromatography is very useful for the analysis of polar ionic compounds. In particular, it is well suited for the separation and quantitation of cephalosporin C derivatives, especially in fermentation broths.In a previous papery we described hydrophobic conditions for the separation of cephalosporin C using a large particle (37-50 icm), medium efficiency C18 column. In a second paper2) we presented an improved method for the analysis of cephalosporin C derivatives using a small particle (10,um), high efficiency column prepared in-house by chemically bonding octadecyltrichlorosilane to silica by an insitu technique. An in-situ column was used because no commercially available column was completely satisfactory for use in the hydrophobic mode. Poor efficiencies and broad asymmetrical peaks are often obtained with commercial columns. In addition, both retention and resolution properties are inadequate, especially with early eluting compounds such as deacetylcephalosporin C and deacetoxycephalosporin C.Cephalosporin C derivatives have been separated by us3) and others4) with reverse phase ion-pair chromatography.The principal advantage of this approach is that early eluting compounds such as deacetylcephalosporin C and deacetoxycephalosporin C are retained on the column long enough to be well separated from interfering substances in fermentation broths. However, with a properly prepared in-situ column as described in this paper, good separations can be obtained without the need for ion-pairing.The work2) that we reported previously on the hydrophobic chromatography of cephalosporin C derivatives employed an in-situ C18 column. However, at that time there was no attempt made to discover the optimum conditions for producing these in-situ columns. This paper gives the results of a study that was carried out on the preparation of C18 columns especially suited for the hydrophobic

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Section: In-situ Columnssupporting

confidence: 91%

Custom made C18 columns for the hydrophobic chromatography of cephalosporin C derivatives.

White¹,

FOX²

1982

J. Antibiot.

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“…The surface concentrations were calculated from the measured carbon contents and the specific surface areas of the C18 chemically modified silica (eq 2) as well as from the surface area values for the underivatized silica (eq 1) as used by other workers (19,(21)(22)(23)25,28,31). Surface concentration as defined by eq 2 is based on micromoles of bonded ligand per meter squared of the chemically modified silica, whereas eq 1 provides surface concentration based on micromoles of ligand per meter squared of underivatized silica.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, most researchers studying retention mechanisms intentionally prepare monomeric C18 materials because of the better understanding of the bonding process, better efficiencies, and the greater reproducibility of the resulting stationary phase (16). Several researchers have J E Í: g determined that the maximum C18 monomeric surface coverage for silica is about 3.5-4.0 µ /m2 (23,24,29). On the basis of the comparison of this value with data in Table I and manufacturers' information concerning the bonding process, materials B and G have polymeric surfaces.…”

Section: Resultsmentioning

confidence: 99%

“…Several recent reports have reviewed the state of the art of chemically bonded alkyl reversed-phase packing materials (14)(15)(16)(17). A number of workers have examined the parameters which may affect the chromatographic characteristics of alkyl bonded materials, i.e., carbon content, length of alkyl chain, surface area, and number of unreacted silanol groups (16,(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). Several studies have shown that the capacity ratio, k', generally increases with increasing carbon content (17,28).…”

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Effect of C18 surface coverage on selectivity in reversed-phase liquid chromatography of polycyclic aromatic hydrocarbons

Wise¹,

May²

1983

Anal. Chem.

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1479 (15) Colby, B. N.; Rosecrance, A. E.; Colby, M. E. Anal. Chem. 1981, 53, (16) Glaser, J. A.; Foerst, D. L.; McKee, G. D.; Quave, s. A,; Budde, W. L. (13) Budde, W. L.: Eichelberger, J. W. "Performance Tests for the Evaluament and Laboratories"; Environmental Protection Agency Report EPA-600/4-80-025, April 1980. (14) Sauter, A. D.; Betowskl, L. D.: Smith, T. R.; Strickler, V. A,; Belmer, R. G.; Colby, B. N.; Wllkinson, J. E. HRC CC J . High Resolut. Chromatogr. Chromatogr. Commun, 1981, 4 , 366-384. tion of Computerized Gas ChromatographylMass Spectrometry Equip-1907-1 91 1 I Envrron. Sci. Techno/. 1981, 15, Recent studles trave reported selectlvlty dlfferences for POlycyclic aromatllc hydrocarbons (PAH) on dlff erent octadecylsllane (C18) reversed-phase llquld chromatographlc columns. I n this paper the differences in llquld chromatographic selectlvllty for various Cts columns were correlated with dlfferences In C,, surface coverage data (as determlned from elemental rinalysis and specific surface area measurements on the C,, modlfled slllca). Slgnlflcant dlfferences In selectlvlty were observed for selected PAH and polyphenyl arenes on monornerlc vs,, polymeric C,, materials. Selectlvlty factors for 50 PAH, alkyksubstltuted PAH, polyphenyl arenes, and polycycllc aromatic sulfur heterocycles were determlned on columns from the same manufacturer from seven dlfferent lots of C,, material with dlfferent C,, surface concentratlons.I n addltlon to priovldlng information concerning the contrlbutlon of C18 surface coverage to retentlon rind selectlvlty In the LC separatlon olf these compounds, these studies provide useful Information regarding the selectlon of the approprlate column to optlniize the separatlon of 'selected polycycllc aromatlc compounds.Reversed-phase liquid chromatography (LC) on chemically bonded octadecylsilane (C18) stationary phases is by far the most popular LC mode for the separation of polycyclic aromatic hydrocarbons (PAH). Reversed-phase LC on Cls phases provides excellent selectivity for the separation of PAH isomers and alkyl-substituted PAH isomers ( I ) . Recently, reversed-phase LC on C18 columns has been specified as the method of choice for the analysis of aqueous effluents for the determination of the 16 PAH on the U.S. Environmental Protection Agency's priority pollutant list (2). In addition to the environmental interest in the determination of PAN by LC, PAH are excellent nonpolar solutes for use in the investigation of reversed-phase LC retention mechanisms.Since Schmit et al. (3) i h t described the separation of PAN on a chemically bonded CI8 phase in 1971, numerous reports of LC retention data for PAH on various C18 columns have appeared. Recent studies by Wise et al. (4), Ogan and Katz (5,6), Colmsjo arid MacDonald (7), and Amos (8) found that Cl8 columns from various manufacturertr not only provided different separation efficiencies but often provided different selectivities and iretention characteristics for PAH. In these studies, attention was focused on three groups of...

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“…Experimental data in the literature does not lend itself to unambiguous interpretation. For instance, it has been shown that plots of both k ‘ and κ against carbon load of the stationary phase are linear, and this indicates that the increase in eluite retention with the carbon load can be due to an increase in either the phase ratio or the equilibrium constant. , …”

Section: Exothermodynamic Relationships Between Thermodynamic Quantit...mentioning

confidence: 99%

Exothermodynamic Relationships in Liquid Chromatography

Vailaya

Horváth

1998

J. Phys. Chem. B

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Exothermodynamic relationships in reversed-phase and hydrophobic interaction chromatography, with the temperature, organic modifier or salt concentration, and carbon number of the eluite and of the stationary phase ligate as the operating variables, are classified and the links between various linear free energy relationships established. Starting from Martin's relationship based on group additivity, we arrive at two linear free energy relationships: one between the logarithmic retention factors, κ, obtained on two different columns with eluites of close structural similarity and the other between κ and the logarithmic octanol−water partition coefficient. Molecular interpretation of classical enthalpy−entropy compensation is offered by the combination of van't Hoff's relationship with linear exothermodynamic relationships between thermodynamic quantities on one hand and properties of the eluite, the eluent, or the stationary phase on the other. Thus, the compensation temperature is expressed by the enthalpy and entropy changes per unit of the above properties. Furthermore, the criterion for the invariance of the compensation temperature is set within the framework of dual compensation. A generalized compensation model is developed to extend the concept of enthalpy−entropy compensation to phenomena involving compensation by any two chromatographic variables by drawing analogies between the dependence of κ on the reciprocal temperature and on other operating variables, such as the organic modifier concentration in the eluent. The existence of 12 different compensation parameters is revealed, each marking the common intersection point of linear plots of free energy versus variables of the retention process. The compensation model leads to 12 three-parameter equations, each describing the retention behavior in reversed-phase chromatography as a function of two chromatographic variables. The family of exothermodynamic relationships encompasses most characteristic features of chromatographic retention and is expected to facilitate the organization, interpretation, and prediction of retention data.

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Behaviour of chemically bonded alkylmethyldichlorosilanes to silica gel in reversed-phase high-performance liquid chromatography

Cited by 87 publications

References 21 publications

Custom made C18 columns for the hydrophobic chromatography of cephalosporin C derivatives.

Custom made C18 columns for the hydrophobic chromatography of cephalosporin C derivatives.

Effect of C18 surface coverage on selectivity in reversed-phase liquid chromatography of polycyclic aromatic hydrocarbons

Exothermodynamic Relationships in Liquid Chromatography

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