What are the points explained by Van deemter model?

The van Deemter equation is a hyperbolic function that predicts that there is an optimum velocity at which there will be the minimum variance per unit column length and, thence, a maximum efficiency. The van Deemter equation was the result of the first application of rate theory to the chromatography elution process.

How do you calculate Van deemter?

The equation H=f(u), the van Deemter equation, is shown in Figure 6. One sees that H has a minimum at an optimum flow velocity that can be determined empirically or by knowledge of A, B, and C (which in many cases is not difficult).

What causes band broadening in chromatography?

The concentration of analyte is less at the edges of the band than at the center. Analyte diffuses out from the center to the edges. This causes band broadening. If the velocity of the mobile phase is high then the analyte spends less time on the column, which decreases the effects of longitudinal diffusion.

What is useful information found from van Deemter equation?

The useful information that can be found from a Van Deemter plot is B. Optimum mobile phase flow rate. This plot and the associated equation is used in chromatography and is used to determine the optimal mobile phase velocity of a given substance.

What do you need to know about the Van Deemter equation?

The van Deemter equation is a theoretical treatment of the peak broadening within a chromatographic column. The equation, which describes the band broadening processes, is given by equation (3). h – reduced plate height, a dimensionless measure of the band broadening.

Where is the minimum plate height at the Van Deemter curve?

The most efficient conditions giving minimum plate height ( Hmin) at optimum flow velocity ( u ― opt) occur at the minimum of the van Deemter curve. Optimum practical gas velocity (OPGV) is located at ∼ 2 × u ― opt.

How is Van Deemter curve related to linear velocity?

Figure 13. van Deemter curve showing the relationship of HETP vs. average linear velocity. The van Deemter curve has a classical shape and is a composite plot of A, B and C terms (plotted below to show their contributions). This diagram is adapted from Reference 9.

How is the Van Deemter equation used to treat HPLC?

A more vigorous treatment similar to the van Deemter equation but developed specifically for HPLC is the Knox equation, 16 which uses a number of reduced parameters where h is the reduced plate height ( h/dp) and v is reduced velocity ( V dp / Dm ).