Stationary phases types

Type Eduet Derivatizing Agent number type Stationary phase type of binding or reaetion... 

The use of hydrothermally formed retaining frits in capillary columns packed with stationary phase particles is an accepted limitation in CEC. The introduction of the frit to hold the packed bed is vital, yet introduces problems such as EOF and flow non-uniformities, compromised frit permeability [87], capillary fragility, increased likelihood of bubble formation [88] and a thermally induced modified frit surface chemistry which can detrimentally alter the chromatography [23]. Practical aspects to be considered include the appreciable effort and skill of the analyst who is required to repeatably manufacture capillaries of a particular phase and redevelop the fritting and packing methodology for each different stationary phase type. 

Stationary Phase Type (a) Mass (kg) Diameter (mm) Effective Void Height Volume (mm) (L) Total Mass (kg)... 

If resolution is not achieved between a critical pair, the use of a shallower gradient can be investigated. If that does not increase the resolution, then a longer column (15-cm column, packed with 3-pm particles of the same stationary phase type) should be used with a reduced flow rate of 0.7 mL/min (due to backpressure limitations). 

In this case study, two different Cl 8 columns from different manufacturers were used. Alternatively, other stationary phase types could also be used such as a polar embedded phase and a Cl 8 phase. Some systems come also equipped with a six-column switcher and in that case, two different types of polar embedded phases, phenyl phase, pentafluorophenyl phases, two different Cl 8 phases (of different bonding density) and an alternate C8 phase could be used. 

A more detailed discussion of the stationary phase types and mechanism of interaction and separation theory in relation to chiral compounds is given in Chapter 22. A large number of chiral stationary phases are currently available to meet the needs of the pharmaceutical industry for determination of the enantiomeric purity of active pharmaceutical ingredients, raw materials, and metabolites. As a consequence, there are a multitude of options in terms of columns, separation mode, and separation conditions to explore in achieving an enantioseparation. 

Stationary phase type Stationary phase material Maximum operating temperature (°C) Separation applications... 

TABLE 3 Chiral Separation Mechanisms, Analyte Requirements, and Modes of Operation for Different Chiral Stationary-Phase Types... 

The suitability of a stationary phase for a particular application depends on the selectivity and the degree to which polar compounds are retarded relative to what their retardation would be on a completely non-polar stationary phase. Since retention time is a function of temperature, flow-rate, stationary phase type and loading or film thickness it cannot be used to relate the retention characteristics of one column to another. Various retention index methods have been described such as evaluating the partition and separation properties of solute-stationary phase systems. Kovats (1958) devised a system of indexing chromatographic retention properties of a stationary phase with respect to the retention characteristics of n-alkanes, alkanes being used as reference materials since they are non-polar, chemically inert and soluble in most common stationary phases [8-10]. The retention index (RI) for the n-alkanes is defined as... 

Most of the stationary phase types in Table 2.8 were derived from popular packed column stationary phases and subsequently modified to allow for immobilization and improved thermal stability. Their selectivity equivalence can be ascertained by comparison of system constants for stationary phases of nominally similar chemical composition in Table 2.6 and 2.8 [125]. There are small differences in selectivity for... 

The stationary phase type for a particular separation is selected based on the requirement that the sample ions and immobilized charged groups of the stationary phase must have complementary properties. The separation is then optimized by adjusting the buffer composition (identity of competing ion, ionic strength, pH), temperature, flow... 

General Classification Specific Melfaod Stationary Phase Type of Equilibrium... 

The development of new selective coatings will continue to yield the greatest overall improvements in SAW vapor sensor performance. The best organic polymer stationary phase type coatings used on SAW sensors are only able to trap about 1% of the vapor molecules presented to them. Clearly, there is much room for improvement. In addition, the list of vapor analytes for which effective SAW coatings have been found will continue to grow. 

It is seen that, as with the other types of LC stationary phases, some experimental work is essential if the optimum conditions to achieve the separation is to be identified. The best stationary phase, solvent, solvent concentration, buffer, buffer concentration and pH must be ascertained, and this can only be achieved by starting from experimentally confirmed conditions for the separation of similar types of solutes. If the sample to be separated is unique, then a rather laborious set of experiments need to be carried following the guidelines given by the supplier of the stationary phases that have been selected for use. It should be pointed out that the recommended procedure will vary between stationary phase types, and between suppliers. 

Stationary Phase Type Trade Name Solvent... 

CEC colvunns can be categorized with respect to the type of stationary phase as OT columns, packed columns, and monolithic columns, as illustrated in Figure 3. It should be noted that a particular CEC stationary phase type can be realized in a fused silica capillary, or in a channel of a microfluidic chip. 

This article deals with the essential theory of LC. Attention is paid to the stationary-phase types. 

Retention in LC depends on retention mechanism and conditions used such as stationary phase type, mobile-phase composition including its pH, flow rate, gradient applied if any, etc. 

There are a wide range of polar stationary phases available for SFC. They include bare silica, cyano, amino, diol, ethylpyridine, and many others. Virtually all chiral stationary phase types have been used in SFC. 

The primary objective in any chromatographic separation is always the complete resolution of the compounds of interest, in the minimum time. To achieve this task, the most suitable analytical column (dimension and stationary phase type) has to be used, and adequate chromatographic parameters must be applied to limit peak enlargement phenomena. A good knowledge of chromatographic theory is, indeed, of great support for the method optimization process, as well as for the development of innovative techniques. 

The sorbent or stationary phase (type of sorbent brand batch number layer thickness particle size binder in layer precoated or homemade type of backing size of channels, if any activation method and temperature impregnation, if any)... 

Total time required for the three steps 4 + 1.5 + 1 = 6.5 horns. Allowing a little extra time for setting temperatures and other preparations, these tests would be feasible in a day. They also help recognize trends and yield similar information as the previously described runs - which stationary phase type, organic solvent, pH level, gradient and temperature are the most suitable to obtain the highest number of peaks. 

Several techniques for adjusting the selectivity of separations that involve more than one column or stationary-phase type. Serially coupled columns and mixed-phase columns can be selectivity-tuned. 

Mobile phase Stationary phase Types of chromatography " Abbreviation Separation... 

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