23-41. Describe how nonlinear partition isotherms lead to non-Gaussian band shapes. Draw the chromatographic peak shapes produced by an overloaded gas chromatography column and an overloaded liquid chromatography column.

In this job, we will sketch the chromatographic peak forms produced by an overloaded gas and liquid chromatography column and explain how nonlinear partition isotherms lead to non-Gaussian band shapes.

Peak with a Gaussian form.

When the partition coefficient K does not rely on the solute concentration on a column, it is said to be "t .

- If we had real columns, K would alter as the concentration of solute increased.

- An isotherm is a graph of ${\mathrm{C}}_{\mathrm{S}}$vs${\mathrm{C}}_{\mathrm{m}}$ at a certain temperature (an ideal isotherm would produce a symmetric peak with a retention time ( ${\mathrm{t}}_{\mathrm{r}}$) that is independent of the solute concentration).

Overload.

- Fronting is a phenomenon that occurs in gas chromatography.

- In liquid chromatography, tailing occurs.

We'll start by drawing a graph of ${\mathrm{C}}_{\mathrm{s}}$vs ${\mathrm{C}}_{\mathrm{m}}$.

The upper and lower isotherms are due to an overloaded column (too much solute in the column).

Fronting peaks (asymmetry factor$\frac{\mathrm{B}}{\mathrm{A}}<1$ ) cause the upper isotherm; the intensity of fronting rises with the amount of extra solute injected.

- Tailing peaks cause a lower isotherm (asymmetry factor$\frac{\mathrm{B}}{\mathrm{A}}>1$ ).

We can now depict the chromatographic peak morphologies that an overloaded gas chromatography column and liquid chromatography column produce: