I have a problem with a tyrosine phophatase assay. First of all the standards all turn blue the same way with malachite green, and secondly some of the standards and samples produce a precipitate with the malachite green solution and molybdic acid. I have hydrocortisone hemisuccinate in some samples, and they all produce a precipitate. I don't have a clue about chemistry as I am a medical student so please!!!! help me!!!!