Retention volume, adjusted corrected

To characterize the relative gas-chromatographic retentions of condensed aromatics and heteroaromatics, inclu g thienothiophenes, benzo[b]thiophene, dibenzothiophene, naphthobenzothiophenes, and anthrabenzothiophenes, a system of indices. In, was proposed, In this system a series of similar linearly condensed hydrocarbons (such as benzene, naphthalene, anthracene, tetracene, pentacene,...) was used as a reference scale. The logarithm of the corrected retention volume (adjusted to 0°), log Ft, depends linearly upon the number of condensed benzene rings (z) in the molecule, both in the polar and nonpolar phases. In is expressed by Eq. (58) ... 

Mobile-phase hold-up volume also equal to the retention volume of an unretained compound Corrected gas hold-up volume Volume of mobile phase in column Net retention volume Total retention volume Adjusted retention volume (Zbrrected retention volume Volume of stationary phase in column Peak width at base Peak width at half height Wall coated open tubular (column)... 

To account for hydrodynamic factors due to a finite pressure drop over the length of the column, the adjusted retention volume is corrected by the pressure gradient correction factor j to give the net retention volume Vn... 

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 ... 

Net retention volume. VN- The adjusted retention volume multiplied by the pressure gradient correction factor. 

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... 

When a GC retention volume is both corrected (for average flow) and adjusted (by subtracting out Vg), a new name and symbol are used. 

The slope of versus retention volume as well as the polydis-persity for narrow MWD samples was sensitive to the choice of delay volume as was reported by Shortt and Wyatt (iO). In fact, Shortt recommended that one approach to determine the correct value of the delay volume is to adjust its value until an acceptable slope of the radius of gyration (Rg) versus is obtained, because is dependent on the concentration whereas the radius is not. Accordingly, the delay volume used was 0.312 mL. 

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). 

Because the definition of the adjusted retention volume was given above, and a related definition of the corrected retention volume was given in Chapter 2 (equation 4), we ought to make sure that these two are not confused with one another. Each has its own particular definition the adjusted retention volume, Fr is the retention volume excluding the void volume (measured from the methane or air peak) as shown in equation 9 the corrected retention volume, Vg, is the value correcting for the compres-... 

The capacity factor k is essentially a corrected retention time (Equation [3.18]) that takes into account variations in mobile phase flow rate and thus provides a more robust indicator of analyte retention for a given combination of stationary and mobile phases. As is a unique property of a given solute A for a given stationary-mobile phase combination, the adjusted (corrected) retention volume V,a (Equation [3.15] (or the corresponding retention time) can be used as a tag for analyte identification. Thus the precision and accuracy of measurement of Vja become important and depend on those of the measurement of flow rate U since in practice retention times rather than volumes are the measured quantities. In response to this limitation of the V,a parameter, the capacity ratio of a solute (k) ) was defined as the ratio of its distribution (partition) coefficient to the phase ratio (Vm/V s) of the column with respect to analyte A ... 

If the volumetric carrier gas flow rate (at the column exit) is measured and multiplied by the retention time, the retention volume, Vjj, is obtained. The adjusted retention volume, V, is the retention volume corrected for the void volume (or mobile phase holdup) of the column. It is obtained by simply subtracting the retention volume of an unretained solute (V ) ... 

Qualitative HPLC methods, using area percent, are used to monitor the disappearance of starting material and the formation of byproduct. Without the inclusion of an internal standard and the calculation of response factors, it is not possible to establish with certainty whether all of the starting material can be accounted for. An internal standard must be stable in the reaction mixture, must not co-elute with any of the components, and must be stable in the mobile phase. Ideally, the internal standard has a retention time about half that of the total analysis time. Internal standardization is extremely useful for kinetic studies. Added to the reaction vessel, samples that are withdrawn at various times will contain identical concentrations of internal standard, and chromatograms can be directly compared or adjusted to identical scales to correct for variation in injection volume. 

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