Peak capacity definition

It is this ordering that gave the concept a theoretical bent as real separations are not ordered the retention times in most separation techniques appear almost random across a range of separation time. The mathematical definition of peak capacity, nc, for an isocratic separation is given as (Grushka, 1970)... 

Constant peak width is recognized to give more peak capacity in LC and the same is true in 2DLC. The use of this equation is interesting in that the number of theoretical plates is not constant across a chromatogram of constant peak width. This is easily shown by recalling the definition of the number of plates as... 

This chapter examines another measure of the space used by 2D separations subject to correlation. Some researchers use the words, peak capacity, to express the maximum number of zones separable under specific experimental conditions, regardless of what fraction of the space is used. By definition, however, the peak capacity is the maximum number of separable zones in the entire space. No substantive reason exists to change this definition. The ability to use the space, however, depends on correlation. In deference to previous researchers (Liu et al., 1995 Gilar et al., 2005b), the author adopts the term, practical peak capacity, to describe the used space. The practical peak capacity is the peak capacity, when the separation mechanisms are orthogonal, but is less than the peak capacity when they are not. The subsequent discussion is based on practical peak capacity. 

The author anticipates that many readers will find the results reported here to be commonplace. If so, then why do we so often report the individual peak capacities of the two dimensions and their product as the 2D peak capacity One answer—the conservative one—is that the latter is indeed the maximum number of peaks that can be separated, in agreement with the definition. A more realistic answer is that it is easy to do and appears more impressive than it really is—especially to those who fund our work. In fact, as a practical metric it is often nonsense. Because orthogonality is so difficult to achieve, especially in 2DLC, the peak capacity is a measure of only instrumental potential, not of separation potential, and consideration of... 

For steady-state zones, where H and N also lack definition, we turned to the peak capacity as a common denominator for different methods. We have learned how to estimate peak capacity for ID separations we now extend this concept to incorporate two axes. For this we must reconsider the matter of spot dimensions when migration occurs along both axes rather than just one. 

Partition coefficient, 9, 10 Partition ratio, 11 time optimization of, 57-58 Peak, definition of, 69 Peak capacity, 18, 19 Pellicular supports, 157 Permeability, 63-64 Phase selection diagrams, 218-219 Phase volume ratio, 11 Pinkerton (ISRP) columns, 225-226 Plate height, 17 Plate number, 14-16 Plate theory, 3, 28 Polarity index, 210, 211 Pore size of LC supports, 157 Porosity, 27 Precision, 99-100 Preparative scale ... 

Since the minimum observed peak spacing, according to the above definitions. Is Xq = peak capacity refers to the number of... 

Cp peak capacity of a column under given elution conditions is the number of peaks that can in principle be fitted into a chromatogram between the unretained solutes (at tg) and the last peak , each peak being separated from its neighbors by twice the peak width Atf, it is difficult to be precise about this definition, e.g., how is the last peak defined, but an ultra-simple treatment gives a lower limit for Cp = N5/4 (Equation [3.27]). 

The enthalpy as a function of time is readily available from, for example, drop calorimetry experiments or from adiabatic calorimeters with incremental temperature increases. Scanning calorimeters, however, furnish the heat capacity of the sample. In these cases, the phase transition shows as a peak and the enthalpy of transition is calculated by integration of the peak area. Traditionally, this is done after constructing a proper baseline under the peak between the start and the end of the peak. The definition of the start and the end of the peak and the shape of the baseline under the peak are somehow arbitrary, particularly when the phase transition is accompanied by a heat capacity change. The enthalpy change at the transition temperature trs can be calculated from the heat capacity curve by... 

Example 3.2.3 The definition of peak capacity (3.2.32) was developed for the case of J j = 1 where the two neighboring peaks were separated by the distance 4tr (where a is an assumed average value of the standard deviations of all profiles). If poorer separation is acceptable, Le. J s < 1, what is an estimate of the peak capacity in a given system ... 

In parallel with the new approaches to generating capacity additions, the utilities, with encouragement from regulators, introduced incentives during the 1980s for reducing load demand. Since the system peak hour load provided the inertia for capacity requirement definition, shaving of the peak became the focus of these incentives. 

A definitive identification of the proteins in each peak is not possible, however, the elution times of the peaks at 13-14 min. and 15 min. are close to the times which would be expected for gamma-globulins and albumins, two of the principal classes of serum proteins. These data also indicate the loading capacity of this column with serum. More than 14 mg. of undiluted serum was injected before evidence of overloading in the form of band broadening and peak distortion was observed. 

Trying to determine which column is ideal for a specific analysis can be difficult with over 1000 different columns on the market [74]. A proper choice implies a definition of parameters such as column material, stationary phase (polarity), i.d., film thickness and column length. Guides to column selection are available [74,75]. The most important consideration is the stationary phase. When selecting an i.d., sample concentration and instrumentation must be considered. If the concentration of the sample exceeds the column s capacity, then loss of resolution, poor reproducibility and peak distortion will result. Film thickness has a direct effect on retention and the elution temperature for each sample compound. Longer columns provide more resolving probe, increase analysis times and cost. 

By definition, all interpretive methods of optimization require knowledge of the capacity factors of all individual solutes. This is the fundamental difference between the simultaneous and sequential methods of optimization (sections 5.2 and 5.3, respectively) and the interpretive methods of section 5.5. Moreover, in the specific cases in which only a limited number of components is of interest or in which weighting factors are assigned to the individual solutes (see section 4.6.1) it is also necessary to recognize the individual peaks (at least the relevant ones) in each chromatogram. In section 5.5 we have tacitly assumed that it would be possible to obtain the retention data (capacity factors) of all the individual solutes at each experimental location. 

After 15 years of service at Crescent, the BESS continues its peak-shaving duty although the battery capacity is somewhat diminished. There is not definite information on the total number of cycles that the battery has experienced. The automated system fimctions so routinely that Crescent tends to forget it is there . 

The reactor stability decreases with increasing values of a, since the fraction converted at the peak temperature is lower when ATa j is higher. One study showed that the allowable value of 9 for a first-order reaction ranged from 2.4 to 1.1 as a increased from about 7 to 70 [11,12]. There have been many other studies of the stability of tubular reactors and batch reactors, and some complex correlations for the stability limit allowing for changes in coolant temperature with length and the thermal capacity of the reactor wall [13]. However, it is generally not necessary to get the exact stability limit. The conservative criterion that 6> < 1 is often used unless calculations for different conditions show that even with 9 > the reactor is definitely stable to all likely disturbances. 

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]. 

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