Question

What useful information can be found from a Van Deemter plot?

(a) Optimum column length

(b) Optimum column temperature

(c) Optimum mobile phase flow rate

(d) The selectivity factor

I got this question in examination.

The origin of the question is Chromatography in chapter Unit Operations of Bioprocess Engineering

Answer 1

The correct answer is (a) Optimum column length

Explanation: The Van Deemter equation is an empirical formula describing the relationship between plate height (H, the length needed for one theoretical plate) which is a measure of column efficiency, and linear velocity (µ) . Smaller plate height values correspond to greater peak efficiencies, as more plates, or analyte partitioning, can occur over a fixed length of a column. The Van Deemter equation is governed by three cumulative terms: (A) eddy diffusion, (B) longitudinal diffusion, and (C) mass transfer. A loss in peak efficiency can be observed as a wider analyte band, and therefore, these three terms can also be viewed as factors that contribute to band broadening.