Dicalcium phosphate

Sir. In dibasic calcium phosphate test of assay. How we can? Pls i nees to talk. First i take 0.3 gm sample and dissolve it in 1 ml of 7 m hcl and 5 ml of water. And add ammonia buffer. And add monark black 2 indicator and titration with 0.1n edta. But results is not good. And titration end point is not good.
Pls guide me. I need assay of dcp. Di calcium phosphate