I cant tell you what type of centrifuge to buy, but I found this on Craigslist for $500.00. The guy lived 7 miles from my house and had 3 of them. I ended up with a 1.5 and a 3 liter rotor. I can spin as little as 500ml in this setup. The ag department of a local university upgraded and got rid of them. They were using them for genetically modifying plants. The only down side is it weighs 650 lbs. He still has one left the last time I talked to him.