Three columns with different lots of packing

[Consumer Products Guy]

For our cGMP validations, historically we've used three columns with different lots of packing. I personally think that's a good idea. But I can't locate which official bulletin detailed that requirement, and I've been asked to locate that. Can anyone point me to that FDA/USP/ORA etc. document that states that?

I know many chromatography companies have method validation kits which include three columns of the same part number, but different lots of packing. So I'm not imagining things. Thanks.

[unmgvar]

i know it is in the ICH guidelines for robustness
http://www.ich.org/fileadmin/Public_Web ... deline.pdf
page 13
it does not state 3 but it says to use different lots, manufacturers
but 3 is always a better number then 2, the french have a say:
"never 2 without 3"