Plate theory of Chromatography

Plate Theory of Chromatography

1. The Nobel Prize in Chemistry 1952 was awarded jointly to Archer John Porter Martin and Richard Laurence Millington Synge " for their invention of partition chromatography ." Richard L.M. Synge Archer J.P. Martin PLATE THEORY OF CHROMATOGRAPHY

2. Nernst Distribution law: “ At constant temperature, a solute distributes itself between two immiscible solvents only in a particular ratio” Partition Coefficient PLATE THEORY OF CHROMATOGRAPHY

3. PLATE THEORY OF CHROMATOGRAPHY

4. The plate theory assumes that the solute, during its passage through the column, is always in equilibrium with the mobile and stationary phases. The column is considered to be divided into a number of cells or plates. Each plate is allotted a specific length and, thus, the solute will spend a finite time in each plate. The size of the cell is chosen to provide sufficient residence time for the solute to establish equilibrium with the two phases. Thus, the smaller the plate, the faster will equilibrium and the more plates there will be in the column. Consequently , the number of theoretical plates contained in a column will be directly related to the equilibrium rate and, for this reason, has been termed the  column efficiency. PLATE THEORY OF CHROMATOGRAPHY

5. P late height H and plate count, or number of theoretical plates, N. The two are related by the equation Plate Height P late Count/ Number of Theoretical Plates Length of Column The efficiency of chromatographic columns increases as the plate count N becomes greater and as the plate height H becomes smaller PLATE THEORY OF CHROMATOGRAPHY

6. PLATE THEORY OF CHROMATOGRAPHY

7. PLATE THEORY OF CHROMATOGRAPHY

8. PLATE THEORY OF CHROMATOGRAPHY

9. PLATE THEORY OF CHROMATOGRAPHY

10. PLATE THEORY OF CHROMATOGRAPHY

11. LIMITATIONS: The plate theory successfully accounts for the Gaussian shape of chromatographic peaks and their rate of movement down a column. The theory was ultimately abandoned in favour of the rate theory, however, because it fails to account for peak broadening in a mechanistic way. PLATE THEORY OF CHROMATOGRAPHY