[Passing]

Titration of the trivalent acid histidine (30ml) with NaOH (c=0,1mol/l). Now I need to calculate c(OH^-) in 2 intervals. One from pH 5-6 and the other one from 6.5-7.5.
How do I calculate that? I know the exact amount of leach used at each points.
Normally it's n(NaOH)=c(NaOH)*V(NaOH) but that's only for an equivalence and not a trivalent acid. Do I need the starting volume of 30ml in any way?