A resource for chromatographers
If there is regular noise in your HPLC baseline then you need to figure out what is causing it before you can find a solution. A good first step is to turn off the pump and monitor the output from your detector. If the noise is still present then the problem is not linked to the flow of mobile phase. For a UV detector the most likely source of the noise is the lamp, either it has aged to a point where it needs replaced, or it is defective. Replacing the lamp should resolve the problem. If the noise stops when the pump is stopped then it is linked to the flow of mobile phase. Likely causes are:
- Trapped air in the flow cell - try flushing with degassed mobile phase, or a strong solvent
- A leak - carefully check your system for leaks and refit or replace the affected part
- Temperature fluctuations - control the temperature
- Incomplete mobile phase mixing - if you are using the HPLC system to mix the mobile phase, try mixing the mobile phase by hand and see if the noise goes away.