The influence of silica structure on reversed-phase retention

Cox, G.B.

doi:10.1016/0021-9673(93)80809-m

Cited by 112 publications

(70 citation statements)

References 40 publications

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“…In such applications, however, complex molecules with acido-basic properties are often analyzed. They may strongly interact with the acidic residual silanols of the support [10,11]. Many studies have been carried out to reduce the number of active residual silanols on silica surfaces and to lower the peak asymmetry [12,13].…”

Section: Introductionmentioning

confidence: 99%

Influence of a buffered solution on the adsorption isotherm and overloaded band profiles of an ionizable compound

Gritti

Guiochon

2004

Journal of Chromatography A

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Section: Introductionmentioning

confidence: 99%

Influence of a buffered solution on the adsorption isotherm and overloaded band profiles of an ionizable compound

Gritti

Guiochon

2004

Journal of Chromatography A

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“…These findings are in agreement with the metal content of the silicas, (see Table II). This gives further evidence that metals promote an increasing acidic nature to the resultant silica [11]. Hypersil is a traditional silica with a high metal content which generates a high acidity phase.…”

Section: Determination Of the Unbonded Silica Ion-exchange Capacitiesmentioning

confidence: 88%

“…Most silica and column suppliers have recently introduced high purity silica via a manufacturing process, which minimises metal contamination of the phase. The presence of metal ions in the silica matrix and on the silica surface has been shown to influence peak shape and efficiency presumably by activating silanol groups (by increasing their acidity) towards an interaction with basic analytes [11]. By reducing the proportion of metal cations in the silica, a more homogenous silanol distribution of non-acidic groups is thought to be present which results in reduced activity towards basic analytes.…”

Section: Introductionmentioning

confidence: 98%

An evaluation of unbonded silica stationary phases for the separation of basic analytes using capillary electrochromatography

et al. 2000

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SummaryIn this work, the use of three HypersiJ unbonded silica phases of different purily, with simple aqueous-organic mobile phase eluents has achieved excellent separations of a basic analyte mixture. LC determination of the ion-exchange capacily of the three silicas highlighted a significant difference in their acidic silanol activily i. e. Hypersil silica > Hypersil BDS silica > Hypurily silica. The total silanol activily for the three phases was very similar. Isocratic CEC analysis on the acidic Hypersil unbonded silica using RP-CEC mobile phase conditions (pH 7.8) generated excellent peak shape, good efficiencies (148-508,000 plates/metre) and baseline separation within 14 min for a mixture of six pharmaceutically relevant basic analytes. The less acidic unbonded silicas gave better peak shapes with reduced analysis times than the Hypersil silica, however baseline separation of the basic analytes was not achieved. Itwas postulated that the separation mechanism with unbonded silica is a balance be~een the analyte's electromobilily and its interaction (i. e. ion-exchange and reversed-phase/adsorption mechanisms) with the silica surface. The magnitude of the interaction is dependent upon the proportion and distribution of acidic silanol groups present on the surface and the pH of the mobile phase.The silica materials exhibited a small, but significant, reversed-phase character thus enabling acid, base and neutral components to be separated within a single run.Excellent CEC retention predictions were achieved by taking into consideration the analyte's electromobilly in CE, its retention factor in LC and the EOF in CEC under identical experimental conditions.The technique has been shown to be truly orthogonal in nature to CE and LC and hence is a big hly complementary and important technique for the analytical chemist.The use of unbonded silica in CEC, with reversed-phase mobile phase conditions, provides an excellent separation technique for the rapid analysis of basic analytes of wide structural diversily (i. e. differing pKo s and log P values).

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“…However, the topic has gained increasing importance [12] and some manufacturers have changed their methods of preparation to give many high quality materials. For example Figure 6 shows one company's progress within the last 15 years.…”

Section: Test Mixture 3 -Chelate Forming Compoundsmentioning

confidence: 99%

HPLC in industry—A well established procedure for characterizing RP-stationary phases

Eymann

1997

Chromatographia

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SummaryA well established totally automated testing procedure for characterization of RP materials is presented. The test is suited to the determination of hydrophobic and silanophilic interactions, as well as trace metal impurities on silica surfaces. It includes measurements of stationary phase stability and shows column performance at two different pH conditions. The very different parameters examined readily reveal batch to batch reproducibility and are therefore suitable for laboratories dealing with quality control and validation of columns.

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The influence of silica structure on reversed-phase retention

Cited by 112 publications

References 40 publications

Influence of a buffered solution on the adsorption isotherm and overloaded band profiles of an ionizable compound

Influence of a buffered solution on the adsorption isotherm and overloaded band profiles of an ionizable compound

An evaluation of unbonded silica stationary phases for the separation of basic analytes using capillary electrochromatography

HPLC in industry—A well established procedure for characterizing RP-stationary phases

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