Hello,
Today, when I analyzed my nectar sample (containing plant secondary metabolites, amino acids and proteins) using a HPLC with a UV detector (220nm) and a SEC column, NaOAC buffer as mobile phase, I got two big negative peaks which are repeatable. Wired to me. I am sure the instrument is all right and no air injected.
Is it possible that any components are fluorescent in the sample which could be excited on UV 220nm?