Column preparation chemically bonded

Capillary columns packed with polysulfoethyl A (prepared by chemical bonding of a polypeptide, poly (2-sulfoethyl aspartamide), to silica particles)... 

Benzalkonium chloride ( ) is used as an antimicrobial preservative in Nasonex. It is quantifiable using a HPLC method with a column that has a cyano group chemically bonded to porous silica particles. The HPLC was equipped with a UV-Vis detector, a 150 mm x 4.6 mm, 3- jm Spherisorb S3 CN column. The mobile phase consisted of 45% acetonitrile in 0.05 M phosphate buffer (pH 6.0). The flow rate was set at 1 mL/min. The following procedure was used for sample and standard preparations. About 2.5 g of Nasonex was transferred into a 25-mL volumetric flask. This was diluted to volume with acetonitrile and... 

The chromatographic procedure may be carried out using (a) two stainless steel columns in series the first (25 cm x 4.6 mm) packed with particles of silica, the surface of which has been modified with chemically bonded hexysilyl groups (5 /im) (Spherisorb C6 is suitable) and the second (25 cm x 4.6 mm) packed with cation exchange resin (10 /an) (Partisil-10 SCX is suitable) (b) as the mobile phase at a flow rate of 1.0 ml/min, a mixture of 25 volumes of acetonitrile, 25 volumes of a phosphate buffer solution prepared by dissolving 58.5 g of sodium dihydrogen orthophosphate... 

A 25cm x 2.1 mm ID Varian MicroPak MCH-10 column, prepared by chemically bonding a monomolecular layer of... 

Chemical stability of carbon over the entire pH range has led to considerable interest in the development of carbon-based stationary phases for RPC. Porous graphitised carbon with sufficient hardness, well-defined and stable pore structure without micropores, which ensures sufficient retention and fast mass transfer can be prepared by a complex approach consisting of impregnation of the silica gel with a mixture of phenol and formaldehyde followed by formation of phenol-formaldehyde resin in the pores of the silica gel, then thermal carbonisation and dissolution of the silica gel by hydrofluoric acid or a hot potassium hydroxide. solution [48. The retention and selectivity behaviour of carbon phases significantly differs from that of chemically bonded pha.ses for RPC. Carbon adsorbents have greater affinity for aromatic and polar substances so that compounds can be separated that are too hydrophilic for adequate retention on a Cix column. Fixed adsorption sites make these materials more selective for the separation of geometric isomers [49]. 

Instead of packed columns, monolithic (continuous bed), analytical, or capillary columns in the form of a rod with flow-through pores offer high porosity and improved permeability. Silica-based monolithic columns are generally prepared by gelation of a silica sol to a continuous sol-gel network, onto which a Cjg or another stationary phase is subsequently chemically bonded. Such columns provide comparable efficiency and sample capacity as conventional columns packed with 5-pm particle materials, but have three to five times lower flow resistance, thereby allowing higher flow rates and fast HPLC analyses. Rigid polyacrylamide, polyacrylate, polymethacrylate, or polystyrene monolithic columns are prepared by in sim polymerization. 

Many hundreds of chemical derivatives of porous silica have been prepared and tested (ll). The ability to fabricate reproducibly a high performance LC column has considerable commercial value. As a result, column manufacturers are apt to be reluctant to convey the chemistry used to prepare the bonded functional group structures, but they often allow users to make educated guesses as to what those structures might be. 

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