Another question to help me solve this problem. When I first started playing with the VREF on the pics I thought you could raise vRef+ above vdd, well looking at the data sheets I learned I was wrong. My next question is can I raise Vref- above ground, say 1.33v or does vref have to be ground. The reason I ask, is because if I divide the output of ph probe amplifier by 3 then I should be able to get the range I want out of it in a 2V swing. If I can set vref+ to 2.354V and Vref- to 1.036V I will get a 2mV/Bit of resolution which I think will work for what I want to do.
It would still be nice to find an AD chip so I do not have to use voltage dividers.

Shawn