EDTA + Eliminating metal ions
Posted: Mon Feb 28, 2005 1:53 pm
Does anyone know a method for cleaning up an HPLC system with metal contamination using EDTA?
Cheers
Cheers
I assume that you are talking about the pump, injector, etc. and not the column. In that case, passivation with 2 molar nitric acid for 20 minutes will clean your system. The acid not only dissolves soluble metal ions, it restores the protective oxide coating on the stainless steel surfaces. When finished, wash with at least two changes of DI water. I use my UV detector to monitor the baseline before and after the acid treatment so I know when the all the acid is washed out.
If your column is contaminated, make a mobile phase of 10 mM EDTA at pH 4 and 30% methanol. Pump this through until the UV baseline is stable. The methanol wets the bonded phase. The pH is important because ferric ions are insoluble above pH 4.
Finally, as a preventative, I have been using 0.5 millimolar pyrophosphate in the aqueous mobile phase. It chelates iron very well, and does not absorb UV at 214 nm. It helped a lot with my phosphopeptide separations.
Cheers,