Plate number maximum

In-column solvents Column size (mm) Theoretical plate number Exclusion limit Poiystyrene PEG Particle size (/urn) Pore size (A) Flow Rate (ml/min) Maximum pressure (kgf/cm ) Maximum temperature (°C)... 

The peak measured for a plate number determination contains additional information about the packing quality of a column. The same peak may also be used to quantify information about the shape as well. The peak width on both sides of the perpendicular through the peak maximum is measured at a height of 10% of the maximum height (see Fig. 14.2). The quotient of the back by the front part of the peak is defined as the asymmetry factor (AF) ... 

FIGURE 6.1 A Poppe plot for the required plate number in conventional HPLC. The parameters are taken from Poppe s original paper (Poppe, 1997). The parameters are maximum pressure AP = 4x 107 Pa, viscosity / = 0.001 Pa/s, flow resistance factor

diffusion coefficient D= lx 1CT9 m2/s, and reduced plate height parameters using Knox s plate height model are A — 1, B— 1.5, C = 0.05. 

Plot a graph of //versus Ti and calculate the optimum gas velocity, the corresponding minimum plate height and the maximum plate number. 

Fig. II. Miniinuin analysi time as a function of the maximum available pressure and (be panicle size. Solid lines represent constant plate numbers (I) 1000 (2) 3000 (3) 20,000 (4) 100,000 (5) 300,000 (6) 1,000,000 dotted lines represent constant particle size stated in micrometers at each line. The columns are operated at minimum plate height of h 2, and the other conditions are as follows v 3,i - 3,ij 0.4cP, < - 1 x 10", - 1 x 10" ...

The main contributions are the sample volume and the profile of the injected band characterized by both the injection volume and the injection time 16, 20, 27, 5). We want to calculate the maximum permissible sample size which causes a relative increase in the zone width by a factor 6, hence a decrease in the efficiency by 0. The sensitivity depends little on the column length at constant plate number if the maximum sample size is used in all cases. 

Increasing the chaotropic counteranion concentration of perchlorate, hexa-fluorophosphate, and tetrafluoroborate in the mobile phase for basic compounds studied led to an increase in the apparent efficiency of the system until the maximum plate number for the column is achieved [153], In Figure 4-57A the efficiency for three basic ophthalmic drug compounds increases relatively fast when the concentration of counteranion BFf was increased from 1 mM... 

Generally, there is little difference between the relationships described by Eqs. (1.10) and (1.11). In both cases in agreement with experiments, the plots show a minimum H corresponding to an optimum velocity of the mobile phase for which the maximum efficiency and highest plate number is found for a given column (Fig. 1..3B). 

Pf is the instantaneous concentration of the strong eluting component in the mobile phase at the outlet of the column at the time the band maximum elutes from the column, Ri. R2 are the retention volumes of sample compounds with adjacent peaks, N is the number of theoretical plates determined under isocratic conditions and T, is the hold-up volume of the column. It should be noted that the correct plate number value cannot be determined directly from a gradient-elution chromatogram using Eq. (1.7) or Eq. (1.8), which assume a constant value of the retention factor A and hence can be applied for isocratic elution only. 

Fig. 1.30. (A) The resolution window diagram for the gradieni-elulion separalion of a mixture of eight phenyluiea herbicides on a Separon SGX. 1.5 tm. silica gel column (150 x 3.3 mm i.d.) in dependence on the initial concentration of 2-propanol in n-hcpiane at ihe slart of the gradicni. A. with optimum gradient volume Vc, - 10 ml. Column plate number N = 5000. compounds as in Fig. 1.23. (B. C) The separation of the eight phenylurea herbicides with optimised gradient-elution conditions (maximum resolution in (A)) with gradients from 12 to 38.6 2 2-propanol in n-hcptanc in 7 min (B) and from 25 to 37.5 2 2-propanol in fi-heptane in 5 min (C). Flow rale I ml/min.

The Nusselt number at the. upper edge of the plate where maximum temperature occurs is determined from [Bar-Cohen and Rohseiiow (1984)]... 

Chromatographic efficiency seems to be linked to the additive-to-surfactant concentration ratio in the micellar mobile phase. The plate numbers increase with this ratio but reach a maximum level (e.g., at pentanol/SDS = 6 and acetonitrile/CTAC= 12). - The organic solvent/surfactant ratio affects the exchange rates of the solute between micelle/stationary and aqueous phases. It also controls the extent of the surfactant coverage and the fluidity of the organic layer on the stationary phase. 

According to Tab. 7.11 a maximum VSP is reached for a total number of plates of approximately 65 and the corresponding flow rate ratios m,. This is more than a twofold increase over the productivity at a plate number of 231. But, in addition to the development of productivity, the specific eluent consumption (EC) has increased. As reported by Jupke (2002) analogue correlations can be found for different particle diameter. With decreasing particle diameter an increase in terms of productivity can be observed, while the total number of stages remains nearly constant. 

Top part, optimization for maximiun production rate of the first component. Bottom part, optimization for maximum production rate of the second component. k = 4. N, optimum plate number Ly, optimum loading factor m, optimum reduced or apparent sample size (Eq. 10.15c) Pr, maximum production rate. 

Jupke et al. also studied the economics of the SMB separation. They determined the specific productivity, the specific eluent consumption and the specific separation costs as functions of the column plate numbers. The specific costs were determined for two different production rates 1000 and 5000 kg/year. They could calculate the optimum plate number for maximum value of the specific productivity. The eluent consumption and the specific separation costs continuously decrease with increasing column plate number. Both are relatively high at the maximum specific productivity. These results are similar to those derived in the case of batch chromatography. The economic optimum is a compromise between the effects of conflicting experimental parameters. 

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