Chromatography retention volume

Elution volume, exclusion chromatography Flow rate, column Gas/liquid volume ratio Inner column volume Interstitial (outer) volume Kovats retention indices Matrix volume Net retention volume Obstruction factor Packing uniformity factor Particle diameter Partition coefficient Partition ratio Peak asymmetry factor Peak resolution Plate height Plate number Porosity, column Pressure, column inlet Presure, column outlet Pressure drop... 

Again it is seen that only when second order effects need to be considered does the relationship become more complicated. The dead volume is made up of many components, and they need not be identified and understood, particularly if the thermodynamic properties of a distribution system are to be examined. As a consequence, the subject of the column dead volume and its measurement in chromatography systems will need to be extensively investigated. Initially, however, the retention volume equation will be examined in more detail. 

By measuring the retention volume of a solute, the distribution coefficient can be obtained. The distribution coefficient, determined over a range of temperatures, is often used to determine the thermodynamic properties of the system this will be discussed later. From a chromatography point of view, thermodynamic studies are also employed as a diagnostic tool to examine the actual nature of the distribution. The use of thermodynamics for this purpose will be a subject of discussion in the next chapter. It follows that the accurate measurement of (VV) can be extremely... 

For chromatography purposes the product of the distribution coefficient and the volume of stationary phase, or stationary phase surface area, gives the corrected retention volume,/, e.,... 

Fig. 17. A schematic of the alkane line obtained by inverse gas chromatography (IGC) measurements. The relative retention volume of carrier gas required to elute a series of alkane probe gases is plotted against the molar area of the probe times the. square root of its surface tension. The slope of the plot is yielding the dispersion component of the surface energy of...

The separation of mixtures involving N-methyl-JLtetrahydropyridines into their pure components by means of gas-liquid chromatography was discussed in a report by Holik et al. (87). They found that, using tris(/3-cyanoethoxymethyl)-y-picoline as the stationary phase, the primary factors involved in the specific retention volumes of these enamines is the electronic effect of a methyl substituent and the nitrogen atom on the carbon-carbon double bond. It was observed that 1,3-dimethyl-Zl -tetrahydropyridine (141) has a smaller specific retention volume and, hence, is eluted before... 

ISEC is a size-exclusion chromatography technique, in which the stationary phase is the CFP to be to characterized [16-18] and the eluates are geometrically well-defined steric probes. From the determined retention volumes in a given solvent and on the basis of suitable morphological models, ISEC analysis provides the... 

Jandera, P. and Churacek, J., Gradient elution in liquid chromatography. I. The influence of the composition of the mobile phase on the capacity ratio (retention volume, band width, and resolution) in isocratic elution — theoretical considerations, /. Chromatogr., 91, 207, 1974. 

Table 7. Influence of temperature on the resolution of 75 mg (67) by chromatography on column B 55). (Vi = retention volume t retention time)...

One of the difficulties with any form of chromatography is that a band of solute is dispersed, becoming less concentrated as it travels through the system. The efficiency of the column is a measure of the amount of spreading that occurs. In the chromatogram in Fig. 2.3b, Vr = the retention volume of a solute and wg = the volume occupied by the solute. This is called the peak width, but remember it means a volume, not a length. 

In exclusion chromatography, the total volume of mobile phase in the column is the sum of the volume external to the stationary phase particles (the void volume, V0) and the volume within the pores of the particles (the interstitial volume, Vj). Large molecules that are excluded from the pores must have a retention volume VQ, small molecules that can completely permeate the porous network will have a retention volume of (Vo + Fj). Molecules of intermediate size that can enter some, but not all of the pore space will have a retention volume between VQ and (V0 + Fj). Provided that exclusion is the only separation mechanism (ie no adsorption, partition or ion-exchange), the entire sample must elute between these two volume limits. 

A complete theory predicting retention times or volumes as function of molecular size has not yet been formulated for gel permeation chromatography. A specific column or set of columns is calibrated empirically to give such a relationship, by means of which a plot of amount of solute versus retention volume (the chromatogram figure below) can be changed into a molecular-size-distribution curve. Generally commercially available narrow... 

Relationships such as Eqs. (45) and (46) have been utilized extensively in correlating solubility properties (such as gas/liquid and liquid/liquid partition coefficients), retention volumes in gas/solid chromatography, capacity factors in high-pressure liquid chromatography, etc.199 200 For instance, gas/liquid partition coefficients for each of 35 different liquid stationary phases were represented with R > 0.985.205 Other applications have been in biochemical and pharmacological areas,199 200 e.g., enzyme inhibition and pollutant effects. 

Calibration of size-exclusion chromatography columns based on the finding that the retention volume of a molecular or particulate species is usually a single-valued function of an appropriate size parameter of this molecule or particle, irrespective of its chemical nature and structure. 

Characteristic of the efficiency of a size-exclusion chromatography set-up in terms of band broadening, defined as N = (y la Y, where Fr is the retention volume of an individual low-molecular-weight compound, and oy is the corresponding full width at 60.7% peak height of the elution peak. 

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