Silanol deactivation

J. Paesen, P. Claeys, E. Roets, and J. Hoogmartens, Evaluation of silanol-deactivated slica-based reversed-phases for liquid chro-magraphy of erythromycin, J. Chromatogr., 630 117 (1993). 

Rutledge, D.R. Abadi, A.H. Lopez, L.M. Liquid chromatographic determination of celiprolol, diltiazem, desmethyidiltiazem and deacetyldiltiazem in plasma using a short alkyl chain silanol deactivated column. J.Pharm.Biomed.Anal., 1994, 12, 135-140 [extracted metabolites, celiprolol LOD 3 ng/mL] Sigusch, H. Henschel, L. Kraul, H. Merkel, U. Hoffmann, A. Lack of effect of grapefruit juice on diltiazem bioavailability in normal subjects. Pharmazie, 1994, 49, 675-679 [pharmacokinetics SPE extracted metabolites flurazepam (IS)]... 

Protein-Pak packings are designed for the size exclusion chromatography of proteins and related compounds. They are based on silica, which is deactivated with glycidylpropylsilane. The diol function prevents the interaction of the target analytes with the silica surface. However, because coverage of the silica surface is always incomplete, residual acidic silanols can interact with the analytes. For this reason, most applications are carried out with a salt concentration above 0.2 mol/liter, which eliminates the interaction of analytes with surface silanols. Protein-Pak packings are stable from pH 2 to pH 8. 

Exhaustive silanization with the most active of silanizing reagents cannot eliminate completely all silanol groups on the i silica surface. Encapsulating the deactivated surface by, ... 

Figure 2.6 Reagents used for the deactivation of silanol groups on glass surfaces. A - disilazanes, B > cyclic siloxanes, and C -silicon hydride polysiloxanes in which R is usually methyl, phenyl, 3,3,3-trifluoropropyl, 3-cyanopropyl, or some combination of these groups. The lover portion of the figure provides a view of the surface of fused silica with adsorbed water (D), fused silica surface after deactivation with a trimethylsilylating reagent (E), and fused silica surface after treatment with a silicon hydride polysiloxane (F).

Snyder and coworkers [6] reviewed the dependence of silanol interactions on the chemical structure of the interacting base. Deductions were based on data of the relative efficacy of amine silanol blocking agents that were more popular at the time the stronger the deactivation effect of the modifier, presumably the stronger its binding to silanols. Stronger interaction of an amine or quaternary ammonium compound was said to be favored by... 

At pH 7.0, ammonium phosphate buffer was found to give similar retention but somewhat improved peak shape as compared with potassium phosphate buffers, presumably because of the superior deactivating effect of the ammonium ion on ionized silanols [72], In contrast, this effect was hardly observed at low pH, probably... 

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