Retention volume specific

Hydiocaibon mistuies containing cyclohexane can be analyzed using gas chiomatogiaphy. Specific retention volumes for several stationary phases have... 

In fact, this procedure can be used for any aliphatic series such as alcohols, amines, etc. Consequently, before dealing with a specific homologous series, the validity of using the methylene group as the reference group needs to be established. The source of retention data that will be used to demonstrate this procedure is that published by Martire and his group [5-10] at Georgetown University and are included in the thesis of many of his students. The stationary phases used were all n-alkanes and there was extensive data available from the stationary phase n-octadecane. The specific data included the specific retention volumes of the different solutes at 0°C (V r(To)) thus, (V r(T)) was calculated for any temperature (Ti) as follows. 

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... 

The net retention volume and the specific retention volume, defined in Table 1.1, are important parameters for determining physicochemical constants from gas chromatographic data [9,10,32]. The free energy, enthalpy, and. entropy of nixing or solution, and the infinite dilution solute activity coefficients can be determined from retention measurements. Measurements are usually made at infinite dilution (Henry s law region) in which the value of the activity coefficient (also the gas-liquid partition coefficient) can be assumed to have a constant value. At infinite dilution the solute molecules are not sufficiently close to exert any mutual attractions, and the environment of each may be considered to consist entirely of solvent molecules. The activity... 

Specific Retention Volume V, Net retention volUM at 0 C for unit weight of stationary phase V, 273 W, T. 

Logarithms of retention indices of alkyl benzenes specific retention volumes of esters, aldehydes and alcohols and retention times of alkanes and alkanes have been correlated with Equations 13 snd 15 or relationships derived from them (l3.). Logarithms of retention times of allyl alkyl ethers on various column packings have also been successfully correlated with Equation 15 (lA). 

Specific retention volume. Vg. The net retention volume per gram of stationary phase corrected to 0°C. 

VR has been used in gas-solid chromatography to represent corrected retention volume (49), whereas corrected retention volume in gas-liquid chromatography is given the symbol VR- Specific retention volume in gas-solid chromatography is V, but in... 

Martire and Riedl and coworkers (8,9) developed a method of determination of complex constants which is less time consuming than the Cadogen-Purnell method, although it makes additional assumptions. They have demonstrated that the specific retention volume of A is related to the association constant by the following equation ... 

The specific retention volume, Vg, the net retention volume per unit mass may be given by... 

Benzene was passed at various temperatures through a gas chromatography column packed with silica gel and the following specific retention volumes (extrapolated to zero sample size) were measured ... 

According to this equation, we can expect to obtain a straight line if we plot In (k/ T) versus 1 /T. This somewhat odd-looking relationship corresponds to the more common procedure of plotting the logarithm of the specific retention volume (Vg) against the reciprocal temperature. Vg is defined as the net retention volume at standard temperature (0 °C) and per unit weight of stationary phase ... 

Figure 3.1 provides an illustration of the relationship between the specific retention volume and the temperature. 

Figure 3.1 Example of the linear dependence of the logarithm of the specific retention volume (eqn.3.U) on the reciprocal temperature. Stationary phase silicone oil 702. Solutes n-alcohols (number of carbon atoms as indicated in the figure). Figure taken from ref. [301], Reprinted with permission.

Figure 3.6 Variation of retention with the composition of the stationary phase in GLC. Stationary phase styrene-butadiene polymer blends and copolymers, the butadiene fraction is plotted on the horizontal axis, (a) Specific retention volumes for three n-alkanes and benzene. V is proportional to the capacity factor, (b) the retention index for benzene. The solid line is calculated from the straight lines in figure 3.6a. The circles (polymer blends) and triangles (copolymers) represent experimental data. Figure taken from ref. [310], Reprinted with permission.

Figure 3.6 illustrates the variation of (a) the specific retention volume (Vff which is proportional to the capacity factor) with the composition of a mixed stationary phase, and (b) the variation of the retention index for benzene with the composition. It is clear from these figures that, whereas straight lines are observed for the variation of the capacity factor with the composition, the retention index varies in a highly non-linear manner. 

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