Retention volume, adjusted specific

Reduced parameters, 66-69 Refractive index (RI) detector, 206-207 Regular solution, 49 Relative retention, 20-21, 22, 77 Repeatability, see Precision Reproducibility, see Precision Resolution, 17-19, 55 Response factors (detector), 104, 125 Response time, 94 Retardation factor, Rf, 71 Retention index of Kovats, 78 Retention ratio, 11, 12, 71 Retention time, 6, 9 Retention volume, 9, 75 adjusted, 10, 75 corrected, 62-63, 75 net, 63, 75 specific, 110 Reverse phase LC, 158 Rohrschneider/McReynolds constants, 137-140... 

Not only variations in the pressure at constant temperature influence column-to-column retention data the role of the column hold-up volume as well as the mass of stationary phase present in the column is also important. The net retention volume caleulated from the adjusted retention volume corrects for the column hold-up volume (see Table 1.2). The specific retention volume corrects for the different amount of stationary phase present in individual colunms by referencing the net retention volume to unit mass of stationary phase. Further correction to a standard temperature of 0°C is discouraged [16-19]. Such calculations to a standard temperature significantly distort the actual relationship between the retention volumes measured at different temperatures. Specific retention volumes exhibit less variability between laboratories than other absolute measures of retention. They are not sufficiently accurate for solute identification purposes, however, owing to the accumulation of multiple experimental errors in their determination. Relative retention measurements, such as the retention index scale (section 2.4.4) are generally used for this purpose. The specific retention volume is commonly used in the determination of physicochemical properties by gas chromatography (see section 1.4.2). 

SP is some free energy related solute property such as a distribution constant, retention factor, specific retention volume, relative adjusted retention time, or retention index value. Although when retention index values are used the system constants (lowercase letters in italics) will be different from models obtained with the other dependent variables. Retention index values, therefore, should not be used to determine system properties but can be used to estimate descriptor values. The remainder of the equations is made up of product terms called system constants (r, s, a, b, I, m) and solute descriptors (R2,7t2, Stt2, Sp2 log Vx). Each product term represents a contribution from a defined intermolecular interaction to the solute property. The contribution from cavity formation and dispersion interactions are strongly correlated with solute size and cannot be separated if a volume term, such as the characteristic volume [Vx in Eq. (1.6) or V in Eq. (1.6a)] is used as a descriptor. The transfer of a solute between two condensed phases will occur with little change in the contribution from dispersion interactions and the absence of a specific term in Eq. (1.6) to represent dispersion interactions is not a serious problem. For transfer of a solute from the gas phase to a condensed phase this... 

For each compound, calculate (a) the adjusted retention volume, (b) the net retention volume, and (c) the specific retention volume (at 0°C). Calculate (d) the resolution between ether and hexane, and (e) between hexane and ethylbenzene. 

GLC determines directly the adjusted retention time, defined by eqn (2.30). It depends, obviously, on K of the solute-solvent system in question. Eqns (2.33), (2.35) and (2.37) transform t n into the specific retention volume, F, [16] which is also a fimction of JT. Taking account of eqns (2.37) and (2.42) the following equation relating K and F, results ... 

The specific retention volume, K, corrects the net retention volume for the amount of stationary phase actually on the column, and the column temperature is adjusted or corrected to 0 °C ... 

Where SP is a solvation p>arameter related with the free energy change such as gas-liquid partition coefficient, specific retention volume or adjusted retention time at a given temperature. The capital letters represent the solutes properties and the lower case letters the complementary properties of the ionic liquids. The solute descriptors are the excess molar refraction E, dipolarity/ polarizability S, hydrogen bond acidity basicity, A and B, respectively, and the gas-liquid partition coefficient on n-hexadecane at 298 K, L. The solute... 

Grit Chambers Industries with sand or hard, inert particles in their wastewaters have found aerated grit chambers useful for the rapid separation of these inert particles. Aerated grit chambers are relatively small, with total volume based on 3-min retention at maximum flow. Diffused air is normally used to create the mixing pattern shown in Fig. 25-44, with the heavy, inert particles removed by centrifugal action and friction against the tank walls. The air flow rate is adjusted for the specific particles to be removed. Floatable solids are removed in the aerated grit chamber. It is important to provide for... 

Engelhardt and Mliller reported on the differences in the physical properties, such as specific surface area, specific pore volume and average pore diameter - and on the different amounts of stationary and mobile phase per unit column volume for various commercially available silica gels. If the retention for various solutes were normalized for these factors, distinct selectivities were still noticed. This could be explained by differences in the surface pH of the silicas. Irregular ones were usually neutral or weakly acidic, whereas the spherical ones were either acidic (pH ca.4) or basic (pH ca.9) (see Table 1.4).To obtain the required and optimum selectivity, the pH of silica gel can easily be adjusted. For basic compounds more symmetrical peak shapes were obtained on silica with a basic character. 

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