Van deemter biography summary

In ideal conditions, this would be displayed on the chromatogram as a single spike. What actually appears on the chromatogram is a triangular peak. The reason a spike is not produced is due to the process of band broadening. As a column gets older, its separation efficiency will drop and natural band broadening will occur. Band broadening can also be affected by inappropriate experimental parameters, especially mobile phase flow rates.

To discuss how flow rates affect band broadening, some background is needed. The efficiency of a column is sometimes defined by the number of plates N a column has.

This equation shows the relationship between peak efficiency and linear velocity and please see the Chromacademy module on band broadening for the proper.

Imagine a column sliced radially into thousands of thin discs; these are the plates. The more plates a column has, the more efficient the column is and the separation between two solutes will be greater. The plate count for a column is not a fixed number, but depends on the flow rate, the mobile phase used and the nature of the solute. N is calculated after a sample has been run and is proportional to the retention time and inversely proportional to the peak width at half-height.

Therefore, a narrower peak gives a higher N value. This is also a measure of column efficiency, and since column length is fixed, a large value of N gives a small value of HETP. In a simplified form, the Van Deemter equation is:. As shown earlier, the aim is to minimise HETP to improve column efficiency. Gas chromatography GC was invented by a team of researchers led by Martin and James at the University of Chicago in the early s.