[Protein-analysis] Freeze-drying using a speedvac

[Anne Baldwin]

We are trying to freeze-dry samples of IgG with formic acid and  
pyridine using a speedvac.  Most samples come out with "whitish  
chunks" on the sides of the tubes that will not re-suspend in water.   
However, on a couple of the samples the vacuum pump was acting up  
(the pressure was very weak) and the samples dried quite nicely and  
re-hydrated without a problem.  Anyone have any ideas how to keep the  
white stuff from precipitating before the sample is dry? Or maybe a  
target pressure to run the speedvac at?
Thanks

A