Theoretical plate defined

N = number of theoretical plates, defined fundamentally for isocratic conditions,... 

The concept of a theoretical plate as used in distillation theory is completely different from the one employed here in distillation the number of theoretical plates defines the ease of separation of two components and represents the number of equilibriiifn states on the equilibrium curve of the... 

This is the ASTM D 2892 test method and corresponds to a laboratory technique defined for a distillation column having 15 to 18 theoretical plates and operating with a 5 1 reflux ratio. The test is commonly known as the TBP for True Boiling Point. 

In their original theoretical model of chromatography, Martin and Synge treated the chromatographic column as though it consists of discrete sections at which partitioning of the solute between the stationary and mobile phases occurs. They called each section a theoretical plate and defined column efficiency in terms of the number of theoretical plates, N, or the height of a theoretical plate, H where... 

Assuming a Gaussian profile, the extent of band broadening is measured by the variance or standard deviation of a chromatographic peak. The height of a theoretical plate is defined as the variance per unit length of the column... 

The number of plates, Np, and the height equivalent to a theoretical plate, HETP, are defined as measures of dispersion effects as ... 

Equation (18) displays the relationship between the column efficiency defined in theoretical plates and the column efficiency given in effective plates. It is clear that the number of effective plates in a column is not aii arbitrary measure of the column performance, but is directly related to the column efficiency as derived from the plate theory. Equation (18) clearly demonstrates that, as the capacity ratio (k ) becomes large, (n) and (Ne) will converge to the same value. 

Consider the (n)th theoretical plate in a GC column, as depicted in Figure 21. The properties of the plate are defined as follows. 

Equation (54) is an explicit expression that defines the temperature change of the detector in terms of the initial concentration of the solute placed on the column and the volume of mobile phase that passes through it. It can be used, with the aid of a computer, to synthesize the different shaped curves that the detector can produce. Employing a computer in the manner of Smuts et al. [23], Scott [24] calculated the relative values of (0) for (v= 74 to 160) with a column of 100 theoretical plates, and for (Ca) ranging from 0.25 to 4 and (4>) ranging from 0.01 to 1.25. The curves are shown in Figure 24. 

Knowing the number of theoretical plates that are required, the length of the column (L) is defined as the product of the number of plates and the variance per unit length of the column (H), i.e.. 

Now, the column length (L) can be defined as the product of the minimum plate height and the number of theoretical plates required to complete the separation as specified by the Purnell equation. 

The plate to plate type calculation is a fundamental procedure wherein the tower is assumed to be composed of theoretical equilibrium plates. The actual plates required are determined from the number of theoretical plates using a predicted overall tower efficiency. The starting point for a tower calculation is usually a specified feed composition, feed temperature, and tower operating pressure. The procedure involves defining the compositions and temperamres on each plate in the tower and subsequently the resultant compositions and temperatures of the product streams. The actual computations, which involve trial... 

A longer column is preferred because of a greater processing capacity nd an increased number of plates, as long as the back pressure does not exceed the upper limit and the nonuniform displacement of the solution and the solvent is not serious. The theoretical plate in HOPC is defined as a section in the column in which equivalently full exchange of all of the polymer components... 

According to Equation 3, the resolution of two peaks in column separation is controlled by three major variables retention defined in terms of the retention factor k column efficiency expressed as the number of theoretical plates N and selectivity characterized by the selectivity factor a [48] ... 

Having defined that the resolution required to separate the critical pair in a specific sample is 4a it is now possible to calculate the number of theoretical plates that are necessary to provide adequate quantitative accuracy. This can be easily carried out using the information provided by the Plate Theory in the chapter 2. Restating figure 10 from chapter 2 as figure 8, it is seen that the retention volume difference between the peaks (Av) is... 

The reduced plate height, h, is defined as the number of particles to a theoretical plate and is given by... 

System suitability tests serve to define the level of electrophoretic performance necessary to ensure valid CE assay results. System suitability of the method was evaluated by analyzing the symmetry of the IB-367 peak, theoretical plates of the capillary, and resolution between IB-367 and IB-300, the closest peak to IB-367. The sample concentration of the method was selected at approximately 0.5 mg/ml to assure symmetry below 3.5 and to assume sufficient sensitivity for detecting low... 

To compensate for, what appeared to be very misleading efficiencies values, the effective plate number was introduced. The effective plate number uses the corrected retention distance, as opposed to the total retention distance to calculate the efficiency. Otherwise the calculation is the same as that used in the normal calculation of theoretical plates. In this way the effective plate number becomes significantly smaller than the true number of theoretical plates for solutes eluted at low k values At high k values, the the two measures of efficiency tends to converge. In this way the effective plate number appears to more nearly correspond to the column resolving power. In fact, it is an indirect way of trying to define resolution in terms of the number of effective plates in the column. 

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