Capacity factors calculation

Void volume and capacity factor Calculation of column efficiency... 

The assumptions that (Zf) is equivalent to the retention volume (V, ), and (ZJ is equivalent to the dead volume (Vjj,) in LC or GC are, in the author s opinion not valid. Furthermore, in practice the development occurs under gradient elution conditions and thus the distribution coefficient (K) is not constant throughout the development, and retention will depend on the homogeneity of the stationary phase layer. Nevertheless, the capacity factor calculated in this way is a parameter that is used in TLC to help identify a solute. The assumption, right or wrong, has little impact on TLC detector design or function.)... 

The same conclusion was drawn from the confrontation of silica gel and CPG used as adsorbents in HPLC columns [19]. Indeed the separation of simple compounds on columns filled with both mentioned materials is similar (see Fig.8) [19], but the comparison of these compounds for their capacity factors calculated per 1 m of the sorbent area in the chromatographic column (Table 1) points out a stronger interaction of the separated molecule with the CPG surface. 

Capacity factor calculated using methanol as the retention marker. 

A regenerative fuel cell is installed to provide constant 2-kW power output from a PV array. The fuel cell system efficiency is 50% (LHV) and the electrolyzer system efficiency is 75% (also LHV). The fuel cell operates 12 hours during the night. During the day the PV array provides 2kW for the load and it runs the electrolyzer. During these 12 hours the electrolyzer operates with 22% capacity factor. Calculate ... 

In a chromatographic analysis of low-molecular-weight acids, butyric acid elutes with a retention time of 7.63 min. The column s void time is 0.31 min. Calculate the capacity factor for butyric acid. 

First we must calculate the capacity factor for isobutyric acid. Using the void time from Example 12.2, this is... 

If the capacity factor and a are known, then equation 12.21 can be used to calculate the number of theoretical plates needed to achieve a desired resolution (Table 12.1). For example, given a = 1.05 and kg = 2.0, a resolution of 1.25 requires approximately 24,800 theoretical plates. If the column only provides 12,400 plates, half of what is needed, then the separation is not possible. How can the number of theoretical plates be doubled The easiest way is to double the length of the column however, this also requires a doubling of the analysis time. A more desirable approach is to cut the height of a theoretical plate in half, providing the desired resolution without changing the analysis time. Even better, if H can be decreased by more than... 

The capacity factors of SN-SiO, for metal ions were determined under a range of different conditions of pH, metal ions concentrations and time of interaction. Preconcentration of Cd ", Pb ", Zn " and CvS were used for their preliminary determination by flame atomic absorption spectroscopy. The optimum pH values for quantitative soi ption ai e 5.8, 6.2, 6.5, 7.0 for Pb, Cu, Cd and Zn, respectively. The sorption ability of SN-SiO, to metal ions decrease in line Pb>Cu> >Zn>Cd. The soi ption capacity of the sorbent is 2.7,7.19,11.12,28.49 mg-g Hor Cd, Zn, Pb, andCu, respectively. The sorbent distribution coefficient calculated from soi ption isotherms was 10 ml-g for studied cations. All these metal ions can be desorbed with 5 ml of O.lmole-k HCl (sorbent recovery average out 96-100%). 

Equation (16) was first developed by Purnell [3] in 1959 and is extremely important. It can be used to calculate the efficiency required to separate a given pair of solutes from the capacity factor of the first eluted peak and their separation ratio. It is particularly important in the theory and practice of column design. In the particular derivation given here, the resolution is referenced to (Ra) the capacity ratio of the first... 

The columns must be designed or chosen such that the critical pair are separated and, as a second priority, the last peak must be eluted in a reasonable time. The first peak in the chromatogram is not considered part of the reduced chromatogram and is included as the dead volume marker from which the capacity factors of each solute can be calculated, together with the separation ratio of the critical pair. 

Having chosen the test mixture and mobile diase composition, the chromatogram is run, usually at a fairly fast chart speed to reduce errors associated with the measurement of peak widths, etc.. Figure 4.10. The parameters calculated from the chromatogram are the retention volume and capacity factor of each component, the plate count for the unretained peak and at least one of the retained peaks, the peak asymmetry factor for each component, and the separation factor for at least one pair of solutes. The pressure drop for the column at the optimum test flow rate should also be noted. This data is then used to determine two types of performance criteria. These are kinetic parameters, which indicate how well the column is physically packed, and thermodynamic parameters, which indicate whether the column packing material meets the manufacturer s specifications. Examples of such thermodynamic parameters are whether the percentage oi bonded... 

Solvent optimization in reversed-phase liquid chromatography is commenced by selecting a binary mobile phase of the correct solvent strength to elute the seuaple with an acceptable range of capacity. factor values (1 < k <10 in general or 1 < k < 20 when a larger separation capacity is required). Transfer rules (section 4.6.1) are then used to calculate the composition of other isoeluotropic binary solvents with complementary selectivity. In practice, methanol, acetonitrile and tetrahydrofuran are chosen as the selectivity adjusting solvents blended in different... 

Standards and blanks are the usual controls used in analytical HPLC. Standards are usually interspersed with samples to demonstrate system performance over the course of a batch run. The successful run of standards before beginning analysis demonstrates that the system is suitable to use. In this way, no samples are run until the system is working well. Typically, standards are used to calculate column plate heights, capacity factors, and relative response factors. If day-to-day variability has been established by validation, the chromatographic system can be demonstrated to be within established control limits. One characteristic of good science is that samples... 

FIGURE 3.13 Dependence on the resolution of two adjacent peaks from the separation selectivity, column efficiency, and capacity factors of peaks. Curves were calculated by keeping values of two parameters constant at the starting value and varying the third parameter. 

Ten columns of the 24 available in a cartridge were employed to analyze all compounds in duplicate. Uracil, was employed as a dead volume marker (tO) needed for the evaluation of retention factor [k = (tr - t0)/t0]. Two additional columns were used for simultaneous analysis of the unknown. Values for the log of the capacity factor k were calculated for every compound at each percent organic content of the mobile phase log k = log [(tr - t0)/t0. For each compound, a plot of log k versus percent acetonitrile was used to calculate log k w (log k at 0% acetonitrile). 

It is a great deal of work to actually determine a true equilibrium constant and most chemical separation methods speak in terms of values which are proportional to the actual equilibrium constant. At constant flow, the time that a given type of molecule is retained is related to the time for the void volume to pass after the sample is placed in a column or on a plate with the addition of the time for the net retention volume. If the flow remains constant, the temperature of the separation remains constant and no stationary phase is gained or lost, one can attempt qualitative identification using retention times. It is more reasonable to calculate the ratio of net retention volume to the void volume and call the result partition factor or capacity factor, k. ... 

Calculate the capacity factor when the retention time of a mixture component is 4.51 min and the retention time of the sample solvent is 0.95 min. Is it within the optimum range Explain. 

Calculate the capacity factor for the two mixture components in problem 49. 

In the case of a binary eluent system the dependence of the capacity factor on the volume fraction of the component with the higher elution strength (C) can be calculated by... 

In a test on a centrifuge all particles of a mineral of density 2800 kg/m3 and of size 5 xm, equivalent spherical diameter, were separated from suspension in water fed at a volumetric throughput rate of 0.25 m3/s. Calculate the value of the capacity factor E. 

While retention time is used for peak identification, it is dependent on the flow rate, the column dimension, and other parameters. A more fundamental term that measures the degree of retention of the analyte is the capacity factor or retention factor (k ), calculated by normalizing the net retention time (% > retention time minus the void time) by the void time. The capacity factor measures how many times the analyte is retained relative to an unretained component. ... 

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