MTT assay trouble shooting - (Apr/02/2013 )

Hi
I performed MTT assay in mouse spleenocytes .... I am getting colour development even in RPMI medium alone wells where in no cell is there
what could be the possible problem.

how to trouble shoot the problem.

I prepared RPMI1640 without phenol red from Sigma according tot eh directions and added FBS to it, filtered and employed it for the assay.

MTT was prepared in PBS

with hello 

i think mtt prepare in Distilled water