Why am I getting peak fronting in my chromatogram?

Peak fronting is when the front edge of a peak rises more gradually than the back edge falls, giving the peak a shape that leans forward. In a normal peak, both sides are roughly symmetrical. Fronting distorts quantification and can cause peaks to overlap.

Column overload

The most common cause. If too much analyte is loaded onto the column, the stationary phase becomes locally saturated. The excess analyte moves through the column faster than the retained portion, producing a front-heavy peak shape.

To fix this, reduce the amount of sample injected. Increase the split ratio if using split injection. Dilute the sample. Or use a column with a thicker film or wider bore, which increases the capacity.

Poor column installation

If the column is not positioned correctly in the inlet or detector, dead volume can cause peak distortion. Check that the column is inserted to the correct depth at both ends and that the ferrules are properly tightened without crushing the column.

Mismatched solvent and column polarity

If the solvent used to dissolve the sample is poorly matched to the column's stationary phase, the solvent can interact with the phase in a way that disrupts the chromatography. This is less common but worth considering if fronting appears only with certain sample preparations.

How to diagnose

If fronting affects all peaks, column overload or installation issues are the most likely causes. If it affects only specific peaks at high concentration, overload is almost certainly the issue. If it affects only certain compounds regardless of concentration, a chemical interaction with the column phase may be involved.