Why is there a change in pH after freeze drying Goat IgG with ammonium bicarbonate buffer but no pH change for rabbit IgG when freeze dried the same?

Thanks

Could you show the reference of this result?

How do you determine the pH of a dried substance?

Hi Sorry no reference that's what I need though. Personnal experience from friends working with the stuff.

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Test the pH of the F/D by re-dissolving in MQ water.

You should check whether the effect is reproducible. During evaporation CO2 and hence, buffer capacity gets lost. However, the proteins themselves are afaik not different enough to result in different pH (I would have to check the sequence to verify that, though). I would rather assume that it is essentially a problem of a non-buffered solution. Small difference of additives or even protein concentration can shift the pH easily.