During blank measurements on the Dumatec 8000, some users may observe unusually high bypass peaks even when no sample is present.
In certain cases, the bypass peak may increase to 4000–6000 area counts, causing unstable baseline conditions or abnormal blank results.
This issue is often intermittent and may appear only during specific carousel positions or after movement of the autosampler.
Autosampler Mechanical Alignment
Improper carousel positioning or slight mechanical resistance may affect gas flow stability during rotation.
In some cases, the bypass peak changes depending on the carousel position.
Rechecking carousel installation and movement smoothness is recommended.
Leak Around the Combustion Area
Small leaks near the combustion tube, sealing area, or gas connections may introduce unstable flow conditions.
Even if the standard leak test passes, very small leaks can still influence blank peak stability.
Flow Controller Instability
The helium flow controller (FC2) may show unstable values during leak tests or blank analysis.
For example, FC2 may normally stabilize near 200, but occasionally rise to 280 or fluctuate after carousel movement.
Contamination Inside the System
Residual combustion products, ash buildup, or contamination around the crucible area may influence gas flow and peak behavior.
Regular cleaning of the combustion area is important for stable operation.
Gas Supply Quality
Low gas purity or unstable gas pressure may also contribute to abnormal bypass peaks.
Recommended gas purity:
- Helium: 99.999%
- Oxygen: 99.995% or higher
Field Recommendation
Before replacing electronic components, first inspect the mechanical condition of the autosampler and confirm stable gas flow behavior.
In many field cases, high bypass peaks are related to minor mechanical or flow stability issues rather than major hardware failure.
