Reversed-phase ion exchange and

This is a simple upgrade of the isocratic system with the facility for gradient elution techniques and greater functionality (Fig. 1.1(b)). The basic system provides for manual operating gradient techniques such as reversed phase, ion exchange and hydrophobic interaction chromatography. Any of the detectors listed above under the isocratic system can be used. 

Selectivity, the ability to isolate a particular analyte or separate a number of components within a mixture, has improved dramatically through the development of bonded-phase column packing materials for reversed-phase, ion-exchange and ion-pair chromatography. More recently, forensic laboratories have been introducing polymeric packing materials because of their selectivity and other physical and chemical properties which are more desirable than those of silica-based materials. 

TLC is a good technique to use when normal-phase solvents provide optimum separation. Typical thin-layer separations are performed on glass plates that are coated with a thin layer of stationary phase. The stationary phases used in TLC encompass all modes of chromatography including adsorption, normal- and reverse-phase, ion-exchange, and size-exclusion." The equipment required is simple and inexpensive. TLC is an ideal technique for the isolation of compounds because of its simplicity. However, for TLC to be successful, the impurity and/or degradant level should be at or above 1%. Any component present below this level is very difficult to isolate on a TLC plate because of higher detection limits. 

There are many ways to classify the types of liquid chromatography. One of these is discussed below. Four types of high pressure liquid chromatography to be discussed here are liquid-solid, bonded reversed phase, ion-exchange, and paired-ion. These are all based on the differences in chemical properties of the materials to be separated. 

RP, lEC, and SEC refer, respectively, to separation by reversed phase, ion-exchange, and ize[Pg.156]

Many, if not most, retentive chromatographic methods have been performed in the displacement mode, including normal-phase, reversed-phase, ion exchange, and metal affinity chromatographies. Much of the recent work has focused on the use of ion exchange displacement chromatography for the preparative purification of biotechnological products. Solutes purified by displacement... 

Chromatographic determination of surfactants can be performed by utilizing different separation modes, such as reversed-phase, ion-exchange and size-exclusion techniques. However, a mixed-mode stationary phase has been developed that is suitable for analyzing anionic, nonanionic and cationic surfactants in a single run [51]. The packing material of the commercially available column consists of 5-p,m particles with a pore size of 120 A and a specific surface area of 300 m g . ... 

Cartridges are the most used format in SPE. They are relatively low in price, mostly disposable, and with few solvent limitations. SPE cartridges can be obtained for normal phase, reversed phase, ion exchange, and mixed mode. 

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