INDEX stationary

The Flat-bed pressure filter (Hydromation Engineering Co. Ltd.) (19) is based on the above principle. The pressure compartment consists of two halves, top and bottom. The bottom half is stationary while the top half can be raised to allow the belt and the cake to pass out of the compartment, and can be lowered onto the belt during the filtration and dewatering stage. The filter can be considered as a horizontal filter press with an indexing cloth in comparison with a conventional filter press, however, this filter allows only the lower face of the chamber to be used for filtration. 

The free oil can be determined by an ion exchange HPLC technique. A solution of the sample in ethyl alcohol is analysed by high-performance ion exchange chromatography using a specially prepared ion exchange resin stationary phase, ethanol mobile phase, and differential refractive index detection. 

Qualitative (identification) applications depend upon the comparison of the retention characteristics of the unknown with those of reference materials. In the case of gas chromatography, this characteristic is known as the retention index and, although collections of data on popular stationary phases exist, it is unlikely that any compound has a unique retention index and unequivocal identification can be effected. In liquid chromatography, the situation is more complex because there is a much larger number of combinations of stationary and mobile phases in use, and large collections of retention characteristics on any single system do not exist. In addition, HPLC is a less efficient separation... 

The CHI parameter approximates the percentage of organic modifier in the mobile phase for eluting the compounds and can be used for high-throughput determination of physicochemical properties (50-100 compounds per day). CHI is a system property index, and depends on the nature of the stationary phase and the organic modifier as well as the pH of the mobile phase for ionizable compounds. 

The HcReynolds abroach, which was based on earlier theoretical considerations proposed by Rohrschneider, is formulated on the assumption that intermolecular forces are additive and their Individual contributions to retention can be evaluated from differences between the retention index values for a series of test solutes measured on the liquid phase to be characterized and squalane at a fixed temperature of 120 C. The test solutes. Table 2.12, were selected to express dominant Intermolecular interactions. HcReynolds suggested that ten solutes were needed for this purpose. This included the original five test solutes proposed by Rohrschneider or higher molecular weight homologs of those test solutes to improve the accuracy of the retention index measurements. The number of test solutes required to adequately characterize the solvent properties of a stationary phase has remained controversial but in conventional practice the first five solutes in Table 2.12, identified by symbols x through s have been the most widely used [6). It was further assumed that for each type of intermolecular interaction, the interaction energy is proportional to a value a, b, c, d, or e, etc., characteristic of each test solute and proportional to its susceptibility for a particular interaction, and to a value x, X, Z, U, s, etc., characteristic of the capacity of the liquid phase... 

Theoretical objections to the use of retention index differences for stationary phase characterization are based on the... 

Polarity is a term that is used in chromatography as an index of the ability of compounds to interact with one another in these various ways. It is applied very freely to solutes, stationary phases and mobile phases. The more polar a molecule, the more strongly it can interact with other molecules through the mechanisms above. If the polarities of stationary and mobile phases are similar, then... 

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