Optimization Higher Resolution

For many chromatographic runs, especially with complex samples, resolution or peak capacity is inadequate for the desired separation. In these cases steps can be taken to improve resolution. These steps are described in this section. If resolution is already adequate, other steps can be taken to do the separation faster without losing resolution. Methods for increasing speed will be described in Section 12.S. 

In Chapter 5 we obtained the following general expression for resolution (see Eq. 5.58) 

The velocity W along the separation axis in chromatography is simply Rv (or u/(l + k )) the difference AW in the velocity of two zones is therefore ( R)v. Thus Eq. 12.29 becomes 

For difficult separation problems, A/ is small and can be reasonably treated (for the moment) as a differential term dR. We note that 

We choose to ignore the negative sign in these equations because we are interested only in the absolute values of AR A(1 /R), and so on. (A change in the sign of AR would occur if the peaks exchanged positions this would not alter resolution and is thus unimportant.) 

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A resolution of 800 600 is necessary (use small font) a resolution of 1024 768 is optimal (use either small or large font) higher resolutions can be used with a 17-inch or larger screen (use large font) a resolution of 1280 1024 distorts the text. 

The files are password- and write-protected only the numbers in the colored cells can be changed. The output was optimized for a screen with 800 X 600 resolution. In order that those who use higher resolutions can adapt the graphics to full-screen size, the password is here divulged smac. ... 

VCD and FTIR spectra should always be obtained on the same samples, the FTIR at higher resolution and optimized S/N to permit computation of deconvolved (resolution-enhanced) spectra (Kauppinen etal., 1981). VCD spectra of biomolecules are often normalized to the absorbance, since concentration and path lengths are rarely known to good accuracy. Because the absorbance coefficients for different molecules will vary, this is only an approximate correction for concentration variation. 

The use of a charged chiral selector is probably the best solution to improve the classical PET when CE is hyphenated with MS. Better solubility, additional electrostatic interactions, and improvement of the stereoselective separation power afforded by the self-mobility of the chiral additives into the BGE are among the numerous advantages of these charged selectors. When electromigration of the chiral species and the analytes are opposite (PFT-countercurrent approach), the mobility difference between free and complexed analytes is increased, leading to a higher resolution than with a neutral chiral selector. In optimized countercurrent... 

All the images and tables from the text in JPEG and PowerPoint formats, optimized for projection with enhanced colors, higher resolution and enlarged fonts for easy reading in the lecture hall. 

Due to the enormous growth in capability and separation power that has occurred over the past two decades, the benefits of HPLC in natural product chemistry may now seem obvious. However, as there is an immense choice of modes and procedures, further scope exists to improve the quality of such separations and achieve even higher resolutions based on even more efficient optimization procedures. For these reasons, a comprehensive overview of the principles and limitations of contemporary separation methods in various steps of purification and analysis of natural products has been presented at the beginning of this chapter. 

The structural elucidation of efflux pumps will undoubtedly facilitate the future search and optimization of EPIs. It will also help clarify the mode of action of EPIs identified in the past using more traditional approaches. However, higher resolution... 

The SAS described are optimized for a resolution of 0.75-1.5°. For higher resolutions up to 0.1° it is necessary to use a different method because of the restriction in size for the plastic injection-molded code disc and mask. One example of an SAS with a higher resolution is shown in Fig. 7.11.11 [13]. 

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