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Accessibility and shielding of silanol surface centers on porous silica beads; UV/vis absorption and fluorescence studies

Paper ID Volume ID Publish Year Pages File Format Full-Text
27346 44017 2011 8 PDF Available
Title
Accessibility and shielding of silanol surface centers on porous silica beads; UV/vis absorption and fluorescence studies
Abstract

The adsorption equilibria of proton accepting and donating analytes on porous silica beads applicable as stationary chromatographic phases were investigated by UV/vis absorption spectroscopy. Fluorescence spectroscopy was utilized to characterize the nature of the species formed at the silica surfaces after adsorption. In order to control the equilibria and states of adsorption the active silanol surface centers were partly shielded by adsorbed water or by two types of polymeric coatings, (i) polymerized 1,4-divinylbenzene (DVB) with loadings of 200 mg and 500 mg DVB/g silica, respectively, (ii) polymerized N,N′-diallyl-l-tartardiamide bis-(4-tertbutylbenzoate) (TBB) with a loading of 135 mg TBB/g silica. Acridine orange, 1,2,7,8-dibenzacridine, 3,4,5,6,-dibenzacridine, and lumichrome were used as fluorescent analytes with proton accepting or donating nitrogen centers. The fluorescence anisotropies show that the adsorbed species at the uncoated silica surface are highly immobilized. Coating considerably reduces the equilibrium constants of adsorption. polymerized N,N′-diallyl-l-tartardiamide bis-(4-tertbutylbenzoate) works much better than polymerized 1,4-divinylbenzene. In the latter case a large amount of polymer is necessary in order to produce a significant effect.

► The adsorption equilibria of proton accepting and donating analytes on porous silica beads applicable as stationary chromatographic phases. ► Substantial shielding of the silanol groups is achieved with two polymer coatings. This procedure reduces the equilibrium constants of adsorption by two to three orders of magnitude and makes the stationary phases suitable for HPLC. ► Characterization the nature of the adsorbed species formed at the silica surfaces by fluorescence spectroscopy and time-resolved spectroscopy. ► The mobility of the adsorbed species at the surface was determined by fluorescence anisotropy.

Keywords
Silica surface; Polymer coating; Adsorption equilibrium; Aza-aromatic adsorptives; Fluorescence anisotropy
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Accessibility and shielding of silanol surface centers on porous silica beads; UV/vis absorption and fluorescence studies
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 220, Issue 1, 30 April 2011, Pages 39–46
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us