[sjkim]

I have a sample which contain Zn: 140 g/l, Fe(II) 10 g/l, K 3g/l, Mn,As,Cl,Ca,Co below 1 g/l
I've been trying to test Zn and Iron and in case of Iron(II), we have got the pretty good result with K2Cr2O7 titration.
However, we have problem case of Zinc, as the below many kind of way;
- under pH 10, titration EDTA -> EBT indicator didn't change color cause of very high Fe(OH)2
- under pH 1.5 titration EDTA -> We can't find proper indicator
I should make calcuration real Zn = EDTA result- Fe(II).
Also I doubt interference of iron when we use ferrocyanide titration. 

Please tell us your solution.