A problem when preparing 75% dioxane solution - (Jun/21/2011 )

Dear all, I am trying to prepare a 75% dioxane solution containing 0.1M sodium phosphate, to play a coupling interaction between 1-aminopyrene and CNBr activated agarose, with reference Jancowski et al, Biochemistry, 15 (23), pp5182-5187, 1976.
However, when I prepare the solution, I just mix 10ml 0.4 M sodium phosphate and 30ml dioxane, but a new phase was clearly generated (about 2ml or so) and after vortex, lots of salts were precipitated in that phase. This phenomenon was not related with the order I mix.
Has anyone had the experience in preparing dioxane salt solution?
It would be highly appreciated if anyone would discuss my problem.
If possible, would you be so kind to send me an email to y.liang03@gmail.com?
Thanks.

are you sure that you weren't supposed to add one volume of 0.1M sodium phosphate to 3 volumes of dioxane?