title: Equation for calculating surface coverage from end-capping of chromatographic bonded phases.
abstract: An equation was derived to calculate the surface density of trimethylsilyl groups (alphaTMS) on bonded chromatographic stationary phases that have undergone primary as well as secondary ('end-capping') chemical modification. The new equation is an extension of that published by Berendsen-de Galan for calculating primary surface coverage and, likewise, alphaTMS is calculated in terms of the carbon content (% by weight) of the bonded material before and after end-capping, specific surface area of the starting silica and structural information (molecular weight and number of carbon atoms) of the anchored groups. The new equation is valuable when a thorough characterization of bonded stationary phases is desirable and, if used along with the Berendsen-de Galan equation, it affords total ligand coverage information. Application of the new equation to correct for measurable carbon content of the starting support leads to a more accurate expression for surface coverage from primary as well as secondary bonding. The scope and limitations of the new equation are discussed.
authors.affiliation: Departamento de Química, Universidad del Valle, Cali, Colombia.
authors.forename: J E
authors.initials: JE
authors.lastname: Sandoval
mesh_terms: D002853:Chromatography, Liquid; D008956:Models, Chemical