Ergosterol Bioassay

[Brandon.McGugan]

Has anyone worked on a ergosterol bioassay for fungal biomass determination 
in soil? I have a few papers on this topic but I would like to communicate 
with someone who has hands-on experience with this bioassay. 
I intend using methanol or ethanol and ultra-sonication for the extraction. 
The soil I'm extracting from is contaminated with a mixture of petroleum 
oils. 
Some of the lighter oil fractions  will come off in the process, therefore 
the sample will have to be cleaned up before injection into the HPLC. I 
intend using a Sep-Pak solid phase extraction cartridge (C18). 
Will this do the job?
Can soil samples be strored under refrigeration/ frozen  without 
significant loss of ergosterol say for 2-3 months?                        
Any suggestions would be appreciated
Thanks 
Brandon
University of Natal
Pietermaritzburg
South Africa.