Resolution values, table

The ionic species of the mobile phase will also affect the separation. This is shown in Table 4.3 by the difference in resolution values for magnesium chloride buffer compared to sodium sulfate buffer. In addition, calibration curves for proteins in potassium phosphate buffers are shallower than those generated in sodium phosphate buffers. The slope of the curve in Sorenson buffer (containing both Na and ) is midway between the slopes generated with either cation alone (1). Table 4.4 illustrates the impact of different buffer conditions on mass recovery for six sample proteins. In this case, the mass recovery of proteins (1,4) is higher with sodium or potassium phosphate buffers (pH 6.9) than with Tris-HCl buffers (pH 7.8). 

Hydrolase-catalyzed resolution of simple 2-methylalkanols by acylation with vinyl acetate in organic solvents proceeds with low to moderate E-values (Table 4.1) [42, 43]. 

The presence of such isomeric solvates may account for the asymmetry noted (62, 6) when carrying out the curve resolution of the 90-MHz spectra, but, within the accuracy attainable, the effect is barely significant. There are discrepancies in the values for the intrinsic shifts of the solvated species recorded by all three groups of workers (but differences between successive solvates are more satisfactory). Toma and co-workers calculated (62) the theoretically expected and isomeric differences between successive solvates, obtaining reasonable agreement with observed values (Table V). 

Representative resolution values are tabulated in Table 1.6. Resolution values are typically greater than 1.5 and are generally expressed as a range of values. 

In the introductory section of this chapter it was shown that a straightforward summation of resolution values does not yield a satisfactory criterion for the evaluation of complete chromatograms (see figure 4.1 and table 4.1). A problem that can readily be appreciated from the example given there, is that the sum of Rs values will be determined mainly by the largest values of Rs that occur in the chromatogram. For example, in the... 

Improvement of the resolution of poorly resolved analytes then could be pursued in two different ways either by increasing the efficiency or by improving the selectivity. The resolution value equal to 1.5 is usually regarded as sufficient for the baseline separation of closely eluted peaks and if we consider that typical average efficiency of modern HPLC column is equal to 10,000 theoretical plates, then we can calculate the selectivity necessary for this separation to get a resolution of 1.5. It will be also useful to compare what would be required in terms of efficiency and selectivity to improve the resolution from 1 to 1.5. Corresponding calculations are shown in the Table 1-1. 

Normally a resolution value much greater than unity denotes but little overlap resolutions of 1.5 and 2.0 for two gaussian peaks of equal size represent overlap of only 0.13 and 0.003%. Table 24-1 indicates the relation between purity and resolution for a variety of binary mixtures. ... 

FIGURE 5.14 The curves represent the scattering power of various atoms, ranging from atomic number 1 to atomic number 90, as a function of sin2 0/X2, that is, as a function of resolution. Values for the scattering factor can be read directly from the graphs (or from tables) and used in the structure factor equation to calculate Fh/a ... 

Tables I and II are compilations of the total number of components estimated by using Equation 11 for the five data sets described above. Input data were the peak counts from a series of simulated chromatograms at five different n values for the three different component numbers. The results of Table I were obtained by a counting of baseline resolved peaks. Because these counts are nearly independent of component amplitude, these data are a rather direct test of the validity of the model and procedure. The results of Table II are, by contrast, based upon a counting of peak maxima and upon a calculation of an empirical resolution R. Table III contains data for a comparison of baseline peal counts from the simulated chromatograms to those predicted by theory.

For the maximization of the correlation coefficient, a simplex with six factors was used. The factors were (i) sample buffer concentration, (ii) injection time, (iii) capillary temperature, (iv) matrix concentration, and electric held strength for (v) injection and for (vi) separation. These variables were chosen because it was demonstrated previously that they were the most relevant in the DNA separation mechanism and performance (resolution) (27). Table 12.1 shows the movements made by the simplex with all variable values and the resulting correlation coefficient (r ). 

Table III. Photoresist Contrast (Relative Resolution) Values. 

At atomic resolution, the number of observables is much higher than at medium or low resolution (see Table 10.1) allowing for the refinement of models with more parameters representing a more detailed description of the structure and the flexibility of the molecule in the crystal, for example by using anisotropic displacements parameters (17, U, 17, instead of isotropic 5-values that are... 

When the separations of the acids within the free and glycine conjugated groups are considered, it is seen that on both columns and thin layers, the cholic acid derivatives are eluted ahead of the derivatives of the deoxycholic and chenodeoxycholic acids, and presumably other dihydroxy bile acids. The derivatives of the lithocholic acid are eluted last. Complete separations of the mono-, di-, and trihydroxy bile acids are not realized even on the thin-layer plates of ion exchangers, and there is no discernible resolution of the various taurine conjugates. This order of elution of the bile acids is opposite to that expected on the basis of their pK values (Table II). Free cholic acid (pK 5.29) would have been expected to be retained longer than the dihydroxy acids (pK 6.18-6.29) which should have been retained... 

The tabular data of Unknowns 1.1 to 1.3 also show small peaks of masses above that corresponding to the molecular weight. These are due to the presence of less-abundant isotopes the carbon-12 found in nature must be accompanied by 1.1% carbon-13. These isotopic peaks are particularly important for deducing the elemental composition of the molecule and its pieces displayed in the mass spectrum (Chapter 2). Elemental compositions can also be determined from the exact mass of the peak (Chapter 6), but the necessary high-resolution instrumentation is less commonly available. The spectra in this book will be shown with unit mass resolution (x-axis), obscuring the fact that isotopic masses differ from integer values (Table A.l, assuming carbon as 12.00(XX)0). 

Assuming that the mass spectrometer has sufficient mass resolution, the computer can prepare accurate ma.ss data on the m/z values from an unknown substance. To prepare that data, the system must acquire the mass spectrum of a known reference substance for which accurate masses for its ions are already known, and the computer must have a stored table of these reference masses. The computer is programmed first to inspect the newly acquired data from the reference compound in comparison with its stored reference spectrum if all is well, the system then acquires data from the unknown substance. By comparison and interpolation techniques using the known reference... 

Resolution of racemic alcohols by acylation (Table 6) is as popular as that by hydrolysis. Because of the simplicity of reactions ia nonaqueous media, acylation routes are often preferred. As ia hydrolytic reactions, selectivity of esterification may depend on the stmcture of the acylatiag agent. Whereas Candida glindracea Upase-catalyzed acylation of racemic-cx-methylhenzyl alcohol [98-85-1] (59) with butyric acid has an enantiomeric value E of 20, acylation with dodecanoic acid increases the E value to 46 (16). Not only acids but also anhydrides are used as acylatiag agents. Pseudomonasfl. Upase (PFL), for example, catalyzed acylation of a-phenethanol [98-85-1] (59) with acetic anhydride ia 42% yield and 92% selectivity (74). 

Table 3-1. Values of enantiomeric resolution of DNP-amino acids in a running electrolyte containing the three fractions 1, 2, and 3 of the cyclo(Arg-Lys-X-Pro-X-(3 Ala) sublibrary separated by preparative HPLC.

The resolution of the bi-naphthol enantiomers was used for simulation purposes. A reference case relative to a 8-column configuration of the SMB, based on the values of operating variables and model parameters shown in Table 9-4 was chosen. 

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