Fronting Peaks

GC Troubleshooting Course

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1 - Basic Steps

2 - Tailing Peaks

3 - Broad Peaks

4 - No Peaks

5 - High Baseline

6 - Unstable Baseline

7 - Carryover/Ghost Peaks

8 - Fronting Peaks

9 - Poor Peak Resolution

10 - Split Peaks

11 - Response Variability

12 - Retention Time Variability

13 - Course Summary & Test

Fronting Peaks

Fronting peaks

Fronting (or leading) peaks occur when the front of a peak shows a gradual increase, followed by a sharp decrease — the reverse of tailing. Though less common than tailing, fronting is a clear sign of a system imbalance and can affect quantitation accuracy.

What Does It Look Like?

A fronting peak appears skewed to the left (gradual rise, sharp fall), may be mistaken for a co-elution or early eluting compound.

 

 

Primary Causes & Fixes:

 

1. Column Overload

Cause: Too much analyte is injected, saturating the stationary phase. This prevents proper interaction and separation, causing front-loaded elution.

Symptoms:

  • Affects large peaks in particular.
  • More noticeable when peak heights are significantly above expected levels.

 

Fixes:

  • Dilute the sample before injection.
  • Increase the split ratio to send less sample onto the column.
  • Use a column with a wider inner diameter (e.g., 0.32 mm instead of 0.25 mm) or a thicker film to increase phase capacity.

Reducing the load often restores normal peak shape immediately.

 

2. Incompatible Stationary Phase

Cause: Analyte-phase mismatch (e.g., non-polar compound on a highly polar column) reduces retention and distorts elution profile.

Symptoms:

  • Only one or two individual peaks show fronting.
  • Usually occurs during method development or when switching column chemistries.

 

Fixes:

  • Select a stationary phase that matches analyte polarity.
  • Check application notes, technical bulletins, or published methods for guidance.
  • For problematic polar interactions consider alternative phases or derivatization of analytes.

 

 

Quick Peak Fronting Troubleshooting Guide

Cause Indication Solution
Column overload Multiple large peaks fronting Dilute sample, increase split ratio, change column
Phase incompatibility One or two peaks affected Select a more suitable stationary phase

 

Best Practices:

  • Use calibration standards to identify peak shape changes early.
  • Don’t rely solely on integration — inspect chromatogram peak shapes regularly.
  • Log method changes and instrument parameters to trace issues efficiently.