Stationary phases optimal linear velocity

From 2.14, it can be concluded that the optimal linear velocity for the use of a 5 pm stationary phase is in the order of 2 mm/s. This is only an approximation as this value also depends on the molecular diffusivity of the analyte. It has been seen in the previous sections that D, even for a given analyte, can change by a factor of 2 to 3 when the temperature or mobile phase conditions are varied and the value for will change proportionally. This is the reason why - 120 has been approximated to 10 without losing any relevant accuracy. The most important information in 2.14 is not the absolute value for as a function of dp, it is rather the fact that is strictly proportional to 1/dp. With that knowledge, it is... 

The A, B, and C terms of Equation (3) symbolize contributions to sample dispersion from the interparticle flow structure A, axial diffusion B, and finite rate of equilibration of the solute between mobile and stationary phases C. The values of the coefficients A, B, and C are obtained from curve fitting of experimental data to Equation (3) for a sufficiently wide velocity range. For very good columns, A = 0.5, B = 2, and C - 0.005 (36). Independent of particle size and solute molecular weight, h reaches an optimal value of 2-3 for a well-packed column, when v is in the range of 3-5. For a given solute, the linear velocity at this optimum increases with decreasing particle size. For example,... 

When compared to conventional GG, the primary objective of fast GC is to maintain suf cient resolving power in a shorter time, by using adequate columns and instrumentation in combination with optimized run conditions to provide 3 10 times faster analysis times [46-48]. The technique can be accomplished by manipulating a number of analysis parameters, such as column length, column internal diameter [ID], stationary phase, Im thickness, carrier gas, linear velocity. 

This is the most important equation in LC because it combines the chromatographic separation parameters selectivity, capacity ratio, and plate number. Since these three terms are more or less independent, one term can be optimized after the other. The selectivity term can be optimized by changing the stationary or the mobile phase k can be influenced by the solvent strength of the mobile phase, and N can be adjusted by changing the column length, particle diameter, or solvent linear velocity m,... 

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