Van Deempter equation

For a capillary column, the "A" term is zero and the column inner radius, r, replaces the particle diameter in the van Deempter equation, resulting in what is known as the Golay equation, so that... 

For open-tubular columns, dp is replaced by d. ) The reduced form of the van Deempter equation is... 

As we will see in Chapter 20, capillary columns are the most widely used in gas chromatography because of their high efficiency due to large numbers of plates. These columns have no packing, and so the eddy diffusion term in the van Deempter equation disappears. For open tubular columns, the modification of the van Deempter equation, called the Golay equation, applies ... 

Knox developed an empirical equation for liquid chromatography that contains a term useful for correcting the deviation from the van Deempter equation. 

A generalized plot of the Van Deempter Equation is illustrated in Fig. 11.3. Each of the terms is plotted individually (A = 0 here, as this figure illustrates a plot for an open tubular column) and their sum is shown as the dashed line with a distorted U-shape. The important feature of the plot is that each chromatographic system will have a minimum value for 7/ as a... 

Figure 11.4 Mechanism of origin of multipath term A of Van Deempter equation.

In Sections 11.7 -11.9 we have seen how interacting parameters of column efficiency and linear flow velocity (the Van Deempter Equation), selectivity, and capacity factor (related to the distribution of analytes between phases under operating conditions)... 

What do the Van Deempter equations look like for packed column chromatography, capillary chromatography, and capillary electrophoresis (hint in the last of these there is no stationary phase) ... 

In GC a plot of the Van Deempter equation is shaped like a severely distorted U. In HPLC using 3 p,m particles its shape is more like the letter L . Explain. 

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