Hello, we are using a PDA detector at 280 nm from the last March, in this period we analyze more than 1000 of samples, now the intensity of the lamp is 6000, and the lamp is over the half use. We think that the cell could be dirty. We cllean it using formic acid, after that the ingensity increase to 30000, the expected value, but after 40 injection decrease again. We are using 20 mM amonium acetate and acetonitrile methanol as eluents. The injections are a culture media derivatizated with DEM to see biogenic amines and amino acids. Someone known what is the problem?. Someone is injecting culture bacteria media?. Thanks a lot.