Example of damaged septa: A septum damaged in this way is the cause of many troubleshooting issues, and septa are in fact one of the most commonly replaced GC consumables.
Tailing Peaks
GC Troubleshooting Course
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
Tailing Peaks
Peak tailing is one of the most common peak shape problems in gas chromatography. While it might seem minor, tailing can lead to poor integration, inaccurate quantification, and reduced resolution — especially for closely eluting compounds.
Tailing typically arises from poor sample introduction, adsorption, or hardware-related issues, and sometimes from inadequate method design for certain analytes.
Here are some things to check:
1. Check Injection Technique
If you’re using manual injection, uneven or slow plunger depression can cause tailing due to uneven sample transfer.
Solution:
- Inject in one smooth, rapid motion
- Consider using an autosampler to improve reproducibility.
- Reduce sample volume if tailing persists.
If you're already using an autosampler, the issue is likely hardware-related.
2. Check for Leaks and Hardware Issues
Leaks or incorrect installations are common physical causes of tailing:
- Leaks: Check inlet and column connections, replace damaged septa, ferrules, or seals.
- Septum wear: Septa become 'cored' over time from repeated needle insertions, allowing leaks or sample backflow. Replace routinely (every ~100 injections).
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Example of clean, undamaged septa
3. Verify Column Installation
Incorrect column installation introduces dead volume, causing peak tailing.
Checklist:
- Reinstall the column to the correct depth in the inlet and detector.
- Make sure both column ends are clean, square-cut, and not jagged or angled.
A straight, 'square' cut at the end of the column is required to ensure good chromatography.
Try to avoid having a jagged edge or cutting at an angle, as this can have an adverse effect on the chromatography and retention reproducibility.
4. Inspect the Inlet Liner and Column
Adsorption or contamination inside the inlet liner or column can lead to tailing, especially for active compounds.
What to do:
- Replace the liner if it’s discolored or contains charred debris (e.g., blackened wool).
- Trim 1–3 inches from the inlet end of the column, reinstall with a fresh ferrule, and re-test.
- If tailing persists, perform a column bake-out (e.g., ramp to 10°C below max temp for 1 hour).
- Consider replacing the column if contamination is extensive.
Liners typically contain silica (glass) wool to aid with injection, but over time these can turn black because of contamination – a sure sign that they need to be replaced (3 liners from the left are dirty).
5. Evaluate Chemical and Method Factors
If tailing affects only specific peaks, the issue could be related to compound chemistry or method parameters.
- Polar or reactive compounds (e.g., acids, amines) are prone to adsorption.
- Stationary phase mismatch may exacerbate tailing.
Solutions:
- Switch to a more inert or polar-compatible column phase.
- Add a derivatisation step to neutralize reactive groups (e.g., methylation or silylation).
Summary: Quick Peak Tailing Troubleshooting Guide
| Potential Cause | Solution |
|---|---|
| Manual injection errors | Use autosampler, inject smoothly |
| Leaks or worn septum | Replace septum/seals, check connections |
| Incorrect column depth or cut | Reinstall column, square-cut ends |
| Dirty liner or inlet | Replace liner, use deactivated wool |
| Column contamination | Trim or bake column, replace if needed; |
| Analyte reactivity | Change column phase or derivatize sample |
Related Resources
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Video: How to Change Liner and Septum
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