I am using aqueous sodium dithionite(in deoxygenated deionised water in an anaerobic chamber) for reducing Fe(III) to Fe(II). My Fe(III) amount is very low and due to limitations I cannot use powdered dithionite.

I realize sodium dithionite is not stable in aqueous solution, and while working in triplicate reactors, the reduction extent is sometimes different in three reactors.

I get the solution prepared and injected into reactors within ~ 10 minutes. But the time difference of injection between three reactors is barely above 2 minutes.

I have seen few papers using unbuffered aqueous dithionite and getting consistent results.

What buffers would be best for this process?