Retention on non-polar adsorbents in liquid—solid chromatography Effect of grafted alkyl chains |
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Authors: | Gy rgy F ti Mary Lisa Belvito Aurelio Alvarez-Zepeda and Ervin sz Kov ts |
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Institution: | Laboratoire de Chimie Technique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne Switzerland |
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Abstract: | The retention of 39 molecular probes was measured on chemically bonded dense layers of (3,3-dimethylbutyl)dimethylsiloxy (DMB) and tetradecyldimethylsiloxy (C14) substituents on silica as a function of the composition of the binary acetonitrile-water eluent. The sign of the “associated system peak” was also noted. The composition dependence of retention, measured as areal retention volume, could be described on both non-polar stationary phases by the two-parameter Snyder-Soczewinski equation and by the three parameter Schoenmakers equation in a broad but restricted composition range. The areal retention volume on the surface with grafted alkyl chains was equal to or higher than that on the non-swellable, smooth, non-polar DMB surface. Additional retention on the C14 surface increased with increasing adsorption force (retention) on the DMB surface and it was a function of the composition of the eluent. A possible interpretation of the sign of the “associated system peak” generated by the injection of a pure solute is also given in terms of salvation of the solute in the mobile phase and in terms of the modification of the non-polar adsorbent by the adsorbed solute. |
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