Chromatography Forum

I ran monoamine detection with HPLC-ECD.
I continuously saw monoamine peaks when I loaded buffer only (without any monoamine powder to setup the standard quantification). The HPLC water, Ringer sand mobile phase do not show any peaks. However, When I load stock and dilution buffer only, I see the monoamine peaks at the correct time points. I really don't understand why the monoamine peaks appear at the chromatogram even I did not load microdialysate or monoamine powders.

Would you give any clues to solve this problem?
Thanks

The first thing that comes to my mind is contamination (e.g. from dust floating around the lab). If this were my problem, I would try making up the buffers in a different lab at least once.