Credit: ACD/Labs
by Baljit Bains, Marketing Communications Specialist, ACD/Labs
In chromatography, nothing is more coveted than a sharp symmetrical shape on a flat baseline—the Gaussian peak. Ideal peak shape is essential to achieve enhanced resolution (Rs) and improved accuracy in quantitative analysis. The allure of the Gaussian peak is heightened by the common occurrence of peak abnormalities (fronting, tailing, and splitting). Peak abnormalities can occur for one, a few, or all peaks and are indicative of whether the problem is arising prior to or after separation. Close attention must be paid to the samples and columns used in chromatography experiments to minimize peak abnormalities.
What is peak fronting?
Peak fronting occurs when an asymmetric peak is broader in the first half and narrower in the second half. Several factors may cause peak fronting:
- Poor Sample Solubility: If the sample has poor solubility, it cannot be evenly dissolved into the mobile phase. This can be resolved by either reducing the injected sample’s volume or the solute’s concentration.
- Column Collapse: This is a sudden physical change in the column which can be due to inappropriate conditions such as the temperature or pH of the column. Column collapse can be avoided by modifying the method so that the column is used within recommended limits, replacing the column with a more robust column, or routinely replacing the column (i.e., every 500 injections).
- Saturation/Overload of the Column: This is where the maximum sample capacity is exceeded, causing saturation of the mobile phase. If this happens, the additional molecules cannot partition between the stationary and mobile phases and will elute faster. This can be prevented by reducing the amount of sample loaded on the column.
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