Bonded phases pellicular

Packings for HPLC can be further described as either pellicular or porous. Pellicular particles are made from spherical glass beads, which are then coated with a thin layer of stationary phase. For example, a porous layer can be deposited onto the glass bead to produce a porous layer or a superficially porous particle. The porous layer can in turn be coated with liquid stationary phase or reacted to give a bonded stationary phase. Pellicular particles are generally less efficient than the porous layer of superficially porous particles. 

Applied Science Labs. Vydac Pellicular silica Pellicular ion exchangers Bonded phases on pellicular beads... 

As an alternative to pellicular materials, microparticulate stationary phases may be used. These are either based on organic resins or on inorganic oxides. The latter class contains bare oxides, as well as chemically bonded phases, which may be synthesized in a way similar to that described in section 3.2.2.1, but the functional end group is now an ionic one. 

Guard columns may be filled either with pellicular material (see Fig. 3-13) of the same bonded phase as the analytical column or with the identical packing material as in the analytical column. Pellicular packings (35-40 /urn)... 

The HPLC of large biomolecules such as proteins and DNA often requires specialized columns packed with wide-pore polymer or silica-based bonded phase with extra-low silanol activity.1215 Alternate approaches are pellicular materials or very small nonporous particles. Some of these columns are packed in PEEK or titanium hardware to allow the use of high-salt mobile phase and to prevent possible protein denaturing by metallic leachates. Further details on bio-separations and application examples are discussed in Chapter 7. 

Repack top of column with pellicular particles of same bonded phase functionality. Continue using the column in reverse flow direction. 

Matthews et al. (109) were the first to report LC of vitamin D metabolites using the pellicular packing ODS-Permaphase and a gradient of methanol and water. With the advent of the microparticulate bonded phases, such as p.Bonda-... 

Honigberg et al (78) tested reversed-phase chromatography for separation of a number of drugs, including hydralazine. The columns contained either octadecyltrichlorosilane or diphenyldichlorosilane, bonded to 37 to 50 Jjn pellicular silica packing. Of the numerous mobile phases tested, the best for separating hydralazine, hydrochlorothiazide, and reserpine was acetonitrile/0.1% ammonium acetate (20 80), pH 7 35. The columns were 1.22 m x 2 3 mm (ID) and the flow rate was 1.4 ml per minute. Detection was by ultraviolet absorption at 25 nm. 

Fig.l Schematic representation of pellicular stationary phases consisting of covalently bonded functional groups at the surface (a), functionalized layer-encapsulating solid particles (b), and functionalized latex particles electrostatically bound to a solid core bearing groups of opposite charge (c). 

Chemically bonded octadecyl groups on a pellicular support was used as stationary phase for the separation of a series of Mitragyna oxindole alkaloids4 with methanol - water (4 1) as mobile phase. 

The first reversed-phase separation of ergot alkaloids was reported by Jane and Wheals in connection with the analysis of LSD. Pellicular beads with chemically bonded octadecyl groups were used in combination with methanol - 0.1% aqueous ammonium carbonate (3 2) as mobile phase However, the mobile phase proposed by Vivilecchia et al.6 for the separation of the dihydro-ergotoxine alkaloids on octadecyl columns (acetonitrile - aqueous ammonium carbonate) has been... 

Totally porous and pellicular silica packings are used in adsorption chromatography for the separation of (usually) non-polar and moderately polar compounds [54-56]. The eluotropic strength of common supercritical fluids is not very high which prevents the elution of polar solutes in a reasonable time and/or with an acceptable peak shape. Mixed mobile phases containing a polar solvent such as methanol, extend the polarity range of compounds that can be eluted but often at the expense of selectivity. Consequently, silica-based, chemically bonded sorbents are the most widely used for the separation of polar and high molecular mass compounds. 

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