Retention temperature calculation

According to this equation, the retention temperature for any particular solute and column should depend only upon the ratio r/F. The retention temperature (TR) may be calculated from the isothermal retention volume by graphical integration of the above equation. 

Values for activation energies and the rate of change at room temperature calculated for these data and the values for retention of folding endurance obtained from the single-temperature (105°C), single-withdrawal time (72 hr) TAPPI method (16) are listed in Table V. 

FIGURE 24-10 Characteristic curves of rfF against retention temperature for the hydrocarbons ranging from propane (1) to octane (6) obtained from the chromatographic system of Figure 24-4. Solid lines, calculated from isothermal data points, experimental. From Harris and Habgood. )... 

Both the In k values and the sorption enthalpies, AHm s, may be determined experimentally from the temperature dependence of retention. To calculate the sorption entropy, the phase volume ratio must be known. However, the thermodynamic data may be regarded simply as formal quantities, since the capacity factors correlate directly with AGm >s via the distribution coefficient according to Eq. (38), and since sorption exhibits both distributive and adsorptive character. 

The data in Table 10.5 were obtained by using a GC column operated at constant temperature. Calculate the Kovats retention indices for sample... 

The flux of each component in each cell is calculated using Eq. (14.1) and Eq. (14.5) since aU compositions and temperatures are known. The temperature of the retentate is calculated from the known liquid enthalpy and the known retentate composition zp, using physical... 

A 1.1.6 These indices are independent of other operating parameters. Kovats Retention Indices calculated from retention times determined on any suitable chromatographic system can be compared directly with those from any other suitable system as long as the liquid phase and the temperature are the same. Published compilations are an excellent source of indices for identification purposes. 

The retention index is calculated by logarithmic interpolation between consecutive alkanes and the data acquired under isothermal analysis conditions. Under linear temperature programming, however, an almost identical system of expressing retention data is the methylene unit concept in which methylene unit (MU) values are determined by linear interpolation between the /i-alkanes eluted before and after the compound (Dalgliesh etal, 1966). For example, a peak eluted midway between C19 and C20 under these conditions would have a MU value of 19.50 and an equivalent retention index calculated from this of approximately 1950. The interrelation of isothermal and temperature-programmed data for a particular type of phase, even under widely different analytical conditions, is possible and both concepts permit very useful comparisons of different sets of available literature data. Relative retention times, on the other hand, can show fairly wide variations in values, especially with regard to temperature, and are less suited for use as literature reference data. 

For estimating purposes for direct-heat drying applications, it can be assumed that the average exit-gas temperature leaving the sohds bed wih approach the final solids discharge temperature on an ordi-naiy unit carrying a 5- to 15-cm-deep bed. Calculation of the heat load and selec tion of an inlet-air temperature and superficial velocity (Table 12-32) will then permit approximate sizing, provided an approximation of the minimum required retention time can be made. 

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 amounts of material released from a damaged plant are usually expressed in fractions of the isotopic quantities in the core. These source terms (meaning source for the ex plant transport) depend on accident physics, amount of core damage, time at elevated temperatures, retention mechanisms, and plate-out deposition of material as it transports from the damaged core to release from containment. This section gives an outline of early source term assessments, computer codes used in calculations, and some comparisons of result.s. 

The basis of chromatography is in the differential migration of chemicals injected into a column. The carrier fluid takes the solutes through the bed used for elution (mobile phase). The bed is the stationary phase. Based on mobility, the retention-time detectors identify the fast and slow-moving molecules. Based on internal or external standards with defined concentration, all unknown molecules are calculated in a developed method by software. GC columns are installed in an oven which operates at a specified temperature. A diagram of an oven with GC column is shown in Figure 7.16. 

The unfortunate conclusion must therefore be that, although calculated predictions of sealing force retention may have some value in some situations, where a temperature drop is concerned, only experience, or experimental testing, is likely to provide anything near the correct answer. 

Halang, W. A., Langlais, R., and Kugler, E., Cubic Spline Interpolation for the Calculation of Retention Indices in Temperature-Programmed Gas-Liquid Chromatography, Ana/. Chem. 50, 1978, 1829-1832. 

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