A new approach to produce a hydride-modIfled support which serves as an Intermediate for the synthesis of chromatographic bonded phases Is Investigated. The procedure, referred to as "sllanlzatlon", Involves the controlled deposition of the hydrolysis product of trlethoxysllane (TES) or related silanes to preferentially form an Sl-H monolayer on Inorganic oxide substrates such as silica. Chemical and spectroscopic, as well as thermal, analyses are employed for the characterization of the Intermediate. This synthetic route was developed to Improve an existing method for producing a surface uniformly covered with active sites required for further modification via SIH addition to terminal olefins. With the new approach the time-consuming processes associated with the previous" ' reported chlorination/reduction procedure are eliminated, i addition to Its greater simplicity, sllanlzatlon with TES provide superior SIH coverages as compared to the previous method. A number of commercially available silica substrates were subjected to an optimum sllanlzatlon procedure, and the resulting materials were further derlvatlzed with 1-octene In the presence of a platinum catalyst. The octyl-bonded phases obtained were shown to have good ligand density as well as enhanced resistance to phase deterioration as compared to conventional octyldlmethylsllyl silicas.

A novel method for the preparation of bonded stationary phases Is described Hi which a hydrocarbonaeeous moiety Is bound to sMca surfaces through a direct sOIcon-carbon linkage. An established method Involving the chlorination and reduction of silica was used to prepare an Intermediate material containing fairly stable silicon hydride species. In the present report, such an Intermediate was reacted with terminal vinyl organic functionalities In the presence of a platinum catalyst. IR and NMR spectroscopic evidence confirmed the attachment of hydrocarbonaeeous ligands onto the sMca surface. Typical alkyl surface densities were 4.4 and 2.5 pmol/m2 for octyl and octadecyl groups, respectively. The extent of coverage was found to be strongly dependent on olefin concentration and reaction temperature. When compared to the corresponding organosllanlzatlon product, the bonded sMca was shown to have improved hydrolytic stabMty toward aqueous solutions containing trlfluoroacetlc acid.

A novel synthetic approach to produce chemically bonded slllca-based chromatographic stationary phases Is presented and discussed. The procedure Involves the preparation of a silica Intermediate containing stable silicon hydride (silane) surface species followed by the catalytic addition of these to organic compounds bearing a terminal vinyl group. This paper deals with the preparation of the hydride Intermediate via chlorination of silica followed by reduction with lithium tetrahydridoalumlnate. Several spectroscopic and thermoanalyt-Ical techniques were used to obtain information regarding the structural characteristics of the surface-reduced silica material. It was found that the surface SIH species formed were hydrolytically stable at low pH and thermally stable in the presence of oxygen at temperatures up to about 450 °C. Postreaction treatment of the hydrlde-derivatized solid with aqueous hydrochloric acid was also found to be essential to remove aluminum byproducts from the silica surface while presumably increasing the extent of silane formation.

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