Bonded-Phase Chromatography BPC

The difficulties encountered in LLC can be overcome by the use of chemically bonded stationary phases or bonded-phases. Most bonded phases consist of organochlorosilanes or organoalkoxysilanes reacted with micro-particulate silica gel to form a stable siloxane bond. The conditions can be controlled to yield monomeric phases or polymeric phases. The former provides better efficiency because of rapid mass transfer of solute, whereas the polymeric phases provides higher sample capacity. BPC can be used in solvent gradient mode since the stationary phase is bonded and will not strip. Both normal-phase BPC (polar stationary, non-polar mobile) and reversed-phase BPC (non-polar stationary, polar mobile) can be performed. The latter is ideal for substances which are insoluble or sparingly soluble in water, but soluble in alcohols. Since many compounds exhibit this behaviour, reversed phase BPC accounts for about 60% of published applications. The main disadvantage of silica bonded phases is that the pH must be kept between 2 to 7.5. However, bonded phases with polymer bases (polystyrene-divinylbenzene) can be used in the pH range of 0 to 14. 

Modern IC uses high efficiency ion-exchange materials and continuous flow through detection after removing the ions that cause the mobile phase to a have a high conductivity at the detector. It consists of a fast, highly efficient resin which has about one-tenth to one-thousandth the sample capacity of the old polystyrene resin. The new method, simply called ion chromatography 

Phytate or inositol hexaphosphate is a potential source of phosphorus present in many grains and seeds. The phytic acid is determined by treating the sample with EDTA and separation and quantitation using anion-exchange column (resin AG 1-X8 and eluent 0.8M NaCl) followed by reaction with a solution of ferric suLfosahcylate. The coloured complex can be observed in the UV range at 300 nm [22]. 

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Bonded-phase chromatography (BPC). To overcome some of the problems associated with conventional LLC, such as loss of stationary phase from the support material, the stationary phase may be chemically bonded to the support material. This form of liquid chromatography, in which both monomeric and polymeric phases have been bonded to a wide range of support materials, is termed bonded-phase chromatography . 

It may be difficult to imagine a liquid mobile phase used with a liquid stationary phase. What experimental setup allows one liquid to move through another liquid (immiscible in the first) and how can one expect partitioning of the mixture components to occur The stationary phase actually consists of a thin liquid film chemically bonded to the surface of finely divided solid particles, as shown in Figure 11.8. It is often referred to as bonded phase chromatography (BPC). Such a stationary phase cannot be removed from the solid substrate by heat, reaction, or dissolving in the mobile phase. 

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. 

Some problems associated with conventional LLC (e.g., the loss of the liquid stationary phase through dissolution in the mobile phase) may be obviated by chemically bonding the liquid stationary phase to the support medium. This type of liquid-liquid chromatography is designated bonded phase chromatography (BPC)(11). Since the properties of bonded phases may differ substantially from those of coated phases, BPC separation characteristics may differ from those of conventional LLC. Many phases have exhibited increased efficiency when bonded to the support medium. Most current reverse phase HPLC work involves the use of stationary phases bonded to microparticles. 

Bonded phase chromatography (BPC) takes place either under normal phase or reverse phase conditions. In reverse phase mode the stationary phase is non-polar while the eluant is polar, e.g. methanol or acetonitrile with aqueous buffers. Bonded phase packings have superceded the classical packings where the stationary phase was distributed over the surface of the support particles and bound simply by physical forces of attraction. However, due to the problems of solvent stripping and limited hydrolytic stability, these classical systems, though developed for a few specialised applications, have been replaced by organo-bonded stationary phase materials. 

Modified partition or bonded-phase chromatography (BPC). Most HPLC stationary phases are chemically-modified silicas, or bonded phases, by far... 

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