Chromatography chemically-bonded phases

D. E. Martire and R. E. Boehm, A unified theory of retention and selectivity in liquid chromatography. 2. Reversed-phase liquid clrromatography with chemically bonded phases , J. Phys. Chem. 87 1045-1062 (1983). 

Berendsen, GE. and de Galan, L., Preparation and chromatographic properties of some chemically bonded phases for reversed-phase liquid chromatography, J. Liq. Chromatogr, 1, 561, 1978. 

The influence of the bonded organic moiety on solute retention has not yet been elucidated and only a very small number of papers discuss the properties and use of such phases so far. The numerous advantages of chemically bonded phases make the application of polar chemically bonded phases with nonpolar eluents quite attractive even if the standardization of these phases may pose problems 106) similar to those encountered in the standardization of aidsorbents as well as of polymeric liquid phases in gas chromatography. A detailed discussion of the properties and chromatographic use of bonded stationary phases is given by Melander and Horvath (this volume). 

Miller, N.T. and Shieh, C.H., Preparative hydrophobic interaction chromatography of proteins using ether based chemically bonded phases, J. Liq. Chromatogr., 9, 3269, 1986. 

C. A. T. Brinkman and G. de Vries, Thin-layer chromatography on chemically bonded phases a comparison of precoated plates, J. Chromatogr., 258 43 (1983). 

S. H. Hansen, P. Helboe, and M. Thomsen, Dynamically modified silica—an alternative to reversed-phase high-performance liquid chromatography on chemically bonded phases, J. Pharm. Biomed. Anal., 2 167 (1984). 

Chemically bonded phases (CBP s) are very commonly used in LC, and occasionally also in GC. Such phases cannot be seen as either a solid or a liquid. The common term [201] used for LC involving such phases is bonded phase chromatography (BPC). To be consistent, the stationary phase identification should follow that of the mobile phase in defining the chromatographic system. Hence, LBPC should be used for liquid chromatography using chemically bonded stationary phases. 

If retardation is caused by adsorption on granular solids or other fixed surfaces, the technique is called adsorption chromatography, as noted above. If the solid surfaces merely act as a scaffold to hold an absorbing liquid (which may be of a chosen polarity) in place—perhaps within the pores of solid particles—we have partition chromatography. Many cases lie between these extremes this occurs whenever the solid acts as a support for liquid but retains some adsorptive activity [7]. A special case exists with chemically-bonded phases (CBPs), which usually consist of a one-molecule thick layer of hydrocarbon (often C18) chemically bonded to the solid surface. (These nonpolar phases are frequently used for nonpolar solutes in RPLC.) Partitioning into such a thin layer is affected by the nearby surface, especially since the configuration and motion of each attached molecule is restricted by its fixed anchor to the surface [8]. 

In order to accomplish the desired separation, the selection of appropriate stationary phase and eluent system is imperative. The most commonly used stationary phases in normal-phase chromatography are either (a) inorganic adsorbents such as silica and alumina or (b) moderately polar chemically bonded phases having functional groups such as aminopropyl, cyanopropyl, nitrophenyl, and diol that are chemically bonded on the silica gel support [16]. Other phases that are designed for particular types of analytes have also... 

The stationary phase is covalently bonded to its support by chemical reaction. A large number of stationary phases can be produced by careful choice of suitable reaction partners. The reversed-phase method described above is the most important special case of chemically bonded-phase chromatography. 

Buszewski, B. 1991. Properties and biomedical applications of packings with high-density coverage of Cl8 chemically bonded phase for high-performance liquid chromatography and solid-phase extraction, J. Chromatog., 538 293-301. 

The column materials bearing bonded alkyl chains are used for reversed phase chromatography, while some of the more polar, chemically bonded phases may be used in the straight phase mode as well as in the reversed phase mode, giving more possibilities for selection of the appropriate chromatographic system. 

The following four types of chromatography are dealt with adsorption liquid-liquid partition chemically bonded phases and dynamically coated phases. It should be emphasized that the borders between the four modes are often rather fluid. 

Porous silica (or silica gel) is by far the most important adsorbent for liquid-solid chromatography and is also the substrate used to prepare most chemically bonded phases, giving it a preeminent position in modem column technology [3-15]. Silica particles are mechanically strong and easily prepared in a wide range of particle size ranges and pore diameters suitable for chromatography. As a substrate for the... 

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