COLL 47 |
| Marie C. Messmer, 3681 Ranee St, Easton, PA 18045 and Matthew C. Henry, Pacific Northwest National Laboratory, P.O. Box 999 / P8-19, Richland, WA 99352. |
| It is widely recognized that binary aqueous solutions used in chromatographic elutions exhibit different chromatographic selectivity. In order to determine the basis for this difference, we have examined the structure of acetonitrile-water solutions in contact with octadecylsiloxane monolayers formed on quartz surfaces. We present experimental evidence using sum-frequency spectroscopy that shows that no order exists in methanol-water mixtures at this interface, while acetonitrile in these mixtures not only adsorbs at the octadecylsiloxane and quartz interfaces, but it also adopts a well ordered structure at the interface. We will discuss these differences in terms of chromatographic selectivity. In addition, the influence of salt concentration on the adsorption of acetonitrile will also be discussed. |
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Vibrational Analyses of Dry and Wet Surfaces
2:00 PM-5:45 PM, Sunday, March 28, 2004 Marriott -- Grand Ballroom H, Oral
Division of Colloid and Surface Chemistry |