Factors Affecting the Resolution

The resolution R is related to the selectivity a (relative retention), the number of theoretical plates N and the capacity factor k by  

R is directly proportional to (a -1). An increase in the ratio of the partition coefficients leads to a sharp improvement in the resolution, which can be achieved, for example, by changing the polarity of the stationary phase for substances of different polarities. 

As the selectivity generally decreases with increasing temperature, difficult separations must be carried out at as low a temperature as possible. 

The change in the selectivity is the most effective of the possible measures for improving the resolution. As shown in Table 2.29, more plates are required to achieve the desired resolution when a is small. 

Here the resolution is directly proportional to the residence time of a component in the stationary phase based on the total retention time. If the components stayed only in the mobile phase (k = 0 ), there would be no separation. 

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Ingendoh, A. Karas, M. Hillenkamp, F. Giessmann, U. Factors Affecting the Resolution in Matrix-Assisted Laser De-sorption-Ionization-MS. Int. J. Mass Spectrom. Ion Proc. 1994, 757, 345-354. 

A time-of-flight spectrometer can be used as a mass analyzer, an ion kinetic energy analyzer, and an ion reaction time analyzer. We will consider here only what factors affect the resolution of the system in mass analysis.74 The same consideration can easily be extended to find the resolution in other analyses. There are at least two kinds of mass resolution. One refers to the ability of the system to separate two ion species of nearly equal masses in the same mass spectrum. This is related to the sharpness of the mass lines, or the full width at half maximum (FWHM) of the mass lines. The other refers to the ability of the system to distinguish two ion species of nearly identical masses, but not necessarily in the same mass spectrum. This latter mass resolution is related to the sharpness of reference points in the mass lines such as the onset flight times of the ion species, and the overall long-term stability of the system. This latter resolution determined also how accurately the instrument can measure the mass of ion species. Although this latter resolution is more closely related to ion kinetic energy analysis and is as important as the former one, we will consider here only the former kind, or the conventional kind, of mass resolution. 

Pure SeMet may be distinguished from Met by its infrared spectrum (Shepherd and Huber, 1969). Identification of SeMet in protein hydrolysates is possible by means of standard amino acid analyzers (Sliwkowski, 1984). SeMet elutes near to, or with, leucine. Major factors affecting the resolution of these two amino acids are temperature and pH. 

The intrinsic one-dimensionality of the powder diffraction experiment implies that every attempt should be made to collect diffraction data with the highest possible resolution. As we established in section 3.6, many factors affect the resolution of the experimental data, the most important being the radius of the goniometer, the wavelength of the used radiation, the receiving slit aperture and the step size or sampling step. 

The total pore volume of the support is a very iitportant characteristic since this volume equals the total separation volume in SBC (in contrast with, e.g., RPC where the elution volume may be regulated by the corposition of the mobile phase (115)). Yau et al. (108) slxiwed tliat the porosity of tl ]e support is a more important factor affecting the resolution than the pore size distribution of supports with narrow pore size distributions. Traditional media for SEC have pore volumes exceeding 95 % of the laead volume and the high porosity contributes very favourably to ttie resolution of these materials... 

EPIDEMIOLOGY The Study in populations of health factors affecting the occuirence and resolution of disease and other health-related conditions. 

Wise, S. A. and Sander, L. C. 1985. Factors affecting the reversed-phase liquid chromatographic separation of polycyclic aromatic hydrocarbon isomers. J. High Resolut. Chromatogr. Commun. 8 248-255. 

Tesafova, E. and Bosdkova, Z., The factors affecting the enantiomeric resolution and racemization of oxazepam, lorazepam and promethazine on macrocyclic antibiotics-bonded chiral stationary phases, Chemia Analityczna, 48, 439, 2003. 

TABLE IV. Factors that Affect the Resolution of Resists for Various Lithographic Options... 

Factors affecting the depth resolution and surface sensitivity in RBS are discussed further in the following section. 

The capacity parameters do not affect the selectivity (a), but they do have an effect on the capacity factor (fc) and hence on the resolution (Rs see eqn.1.22). The physical parameters only affect the resolution through the efficiency (N). They also have an effect on the retention time through the hold-up time t0 (see eqn.1.6). 

The most important drawback of the first TOF analysers was their poor mass resolution. Mass resolution is affected by factors that create a distribution in flight times among ions with the same m/z ratio. These factors are the length of the ion formation pulse (time distribution), the size of the volume where the ions are formed (space distribution), the variation of the initial kinetic energy of the ions (kinetic energy distribution), and so on. The electronics and more particularly the digitizers, the stability of power supplies, space charge effects and mechanical precision can also affect the resolution and the precision of the time measurement. 

Another factor affecting the mapping pattern is the source design. Short-arc (xenon and metal halide) lamps can be considered point sources, which generate bulls-eye patterns whereas long-arc lamps (xenon and fluorescent) will produce oblong patterns. Low-resolution mapping tends to obscure these differences, which are real. How pertinent these results will be to an individual study will depend on a number of factors, one of which will be the samples physical size. 

Resolution in SEC. The term resolution in this section refers to any factors affecting the SEC separation when applied to macromolecules. As the distribution coefficient is limited to the range 0 to 1, Giddings estimated that an SEC column could only accommodate a limited number of peaks (peak capacity), estimated as 20 analytes base to base. An SEC... 

As with angle-dispersive neutron diffractometers, the design of TOE powder diffractometers can be optimised for either high resolution or high intensity or some compromise of both. An understanding of the factors that affect the resolution is therefore important. The relative uncertainty in (i-spacing, hdjd, may be determined from the equation ... 

There are some factors affecting the choice of column equipment in order to obtain a good separation. The length of column is necessary more than 30 times the diameter of column, because the resolution increases at the square root of column length. That is why a longer column is used for gel filtration especially for an analytical fractionation. A bed length of more than 1 m is not useful and effective for industrial separation. 

Since the nature of the solvent chosen affects all the three factors viz. a, N and k which affect the resolution, the need of keeping this aspect in mind while making choice of an appropriate solvent (i.e. the one that maximizes resolution) cannot be over emphasized. 

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