Specific resolution factor

Peedc-to-peak resolution in SEC can be calculated by the ratio of peak separation at the peak maxiaut to the sum of the baseline peak widths. This general definition of resolution is less useful in SEC, where a measure of the ability of the column to separate solutes of different molecular weight is required. For this purposes, we define a new term, the specific resolution factor, R, which relates peak resolution to sample molecular weight, assuming all measurements are made within the linear region of the molecular weight calibration curve, equation (4.41)... 

Yau et al. [15] developed the concept of specific resolution factor, / ,p, that can be used for direct comparison of resolution power of unit length of various columns ... 

The specific resolution factor, Rsp in SEC, relates peak separations to sample molecular weight, assuming all measurements are made within the linear region of the molecular weight calibration curve, Eq. (4.30)... 

Column effects. In order to establish optimal operating conditions, it is useful to consider the effects of system parameters on the resolution characteristics of an HDC system. HDC has been described as a chromatographic method with very low capacity but very high efiBciency. For example, the calibration curves show that the spectrum of sizes from less than 100 nm to greater than 300 nm is encompassed in less than about 5% of the column void volume. On the other hand, the theoretical plate count corresponding to the marker peak is typically in the range of several thousand per foot. Comparisons in terms of the specific resolution factor, enable a more precise analysis, since both the separation factor and peak dispersion are included in its definition. A simple form for the specific resolution between two particle populations of diameter Dpi and Dp2 is [11]. 

Fig. 3. Comparison of a high-throughput separation (left) with a conventional CPC separation (right). The efficiency of the CPC separation of PSS polystyrene standards is comparable in both cases the specific resolution factor is 4.3 for the Highspeed column as compared to 4.7 for the conventional analytical column.

Table 2 gives chromatographic data for different classes of enantiomeric dmgs resolved by P-CD bonded phases (8). Drugs for which resolution factors (R) greater than 1.0 were obtained include mephenytoin, ketoprofen, chlorpheniramine, and the barbiturates mephobarbital and hexobarbital. Cyclodextrin-bonded phases provide a rapid and specific technique for the pharmacological evaluation of racemic dmgs. 

In the elucidation of retention mechanisms, an advantage of using enantiomers as model templates is that non-specific binding, which affects both enantiomers equally, will cancel out. Therefore the separation factor (a) uniquely reflects the contribution to binding from the enantioselectively imprinted sites. As an additional comparison, the retention on the imprinted phase is compared with the retention on a non-imprinted reference phase. The efficiency of the separations is routinely characterised by estimating a number of theoretical plates (A), a resolution factor (Rs) and a peak asymmetry factor (As) [10]. These quantities are affected by the quality of the packing and mass transfer limitations, as well as the amount and distribution of the binding sites. 

Chromatographic Separation. With respect to chromatographic techniques, specificity can be demonstrated by a sufficient separation of the substances present. For the assay, appropriate separation means an adequate resolution between the peak of interest and other peaks (e.g., impurities, placebo or matrix components), which need not to be separated from each other. In contrast, universal procedures for the determination of impurities require a sufficient separation of all relevant impurity peaks. The required resolution is strongly dependent on the difference in the size of the corresponding peaks as well as on their elution order. Therefore, if separation factors are determined, the typical concentration levels or the specification limits (as worst case) of the impurities should be maintained. Resolution factors can be calculated according to EP [Eq. (3)] and USP [Eq. (4)] at half height and at the baseline, respectively. However, this is only sensible for baseline-separated peaks. The USP approach is less sensitive toward tailing, but more complex to determine. 

Specific surface areas were determined by the BET method from the nitrogen adsorption at 77 K, using an automatic Micrometries ASAP 2000. Palladium metal dispersion was determined by the dynamic pulsed hydrogen chemisorption. The metallic average particle size of palladium was examined by a transmission electron microscope (JEOL 100 CX) with a resolution factor of 0.3 nm. Chemical analysis allowing the... 

A standard Raman or infrared microspectrometer consists of an excitation source, a compound microscope, a spectrometer, and a detector. As in bulk techniques, the design of microspectroscopic experiments is guided by the sample composition as well as demands for frequency response, sensitivity, data acquisition rates, and spectral resolution. Factors specific to vibrational microspectroscopy include the spatial resolution and the optical throughput between the microscope and the spectrometer. 

The choice of the particular upward pathway in the kinetic resolution of rac-19, that is, the specific order of choosing the sites in ISM, appeared arbitrary. Indeed, the pathway B C D F E, without utilizing A, was the first one that was chosen, and it led to a spectacular increase in enantioselectivity (Figure 2.15). The final mutant, characterized by nine mutations, displays a selectivity factor of E=115 in the model reaction [23]. This result is all the more remarkable in that only 20000 clones were screened, which means that no attempt was made to fully cover the defined protein sequence space. Indeed, relatively small libraries were screened. The results indicate the efficiency of iterative CASTing and its superiority over other strategies such as repeating cycles of epPCR. 

In their fundamental paper on curve resolution of two-component systems, Lawton and Sylvestre [7] studied a data matrix of spectra recorded during the elution of two constituents. One can decide either to estimate the pure spectra (and derive from them the concentration profiles) or the pure elution profiles (and derive from them the spectra) by factor analysis. Curve resolution, as developed by Lawton and Sylvestre, is based on the evaluation of the scores in the PC-space. Because the scores of the spectra in the PC-space defined by the wavelengths have a clearer structure (e.g. a line or a curve) than the scores of the elution profiles in the PC-space defined by the elution times, curve resolution usually estimates pure spectra. Thereafter, the pure elution profiles are estimated from the estimated pure spectra. Because no information on the specific order of the spectra is used, curve resolution is also applicable when the sequence of the spectra is not in a specific order. 

For major point sources, site-specific population patterns were extracted from U.S. Census Bureau files using data at the Enumeration District/Block Group (ED/BG) level. These data provide the finest resolution of population patterns available. The data were scaled from 1970 to a base year of 1978 using county growth factors published by the Census Bureau. Interpolations of population and concentration patterns were used to develop patterns of exposure/dosage that were then summed to produce source-specific exposure/dosage totals. 

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