jkubeika wrote:
I haven't managed to get anywhere with this problem yet. I am at the PA state lab and am waiting for my purchase request for different solvents to get through the red tape (at this time of year with budget pending it is a LONG wait). I have done a study and confirmed that it is only extracted analytes that are degrading. I have tested prepared standards (same exact vials I use to spike) over time in only ethyl acetate and they do degrade, but not nearly at the same rate. It takes 7-10 days of sitting out to drop under 40% recoveries.
I have had our micro lab test the equipment and they have been unable to grow or detect anything that may be eating the analytes.
If a company is using bacteria to produce acetic acid and ethyl acetate from ethanol, any residual enzymes would cause PAH degradation.
A team of volunteers/members of AOAC International were developing a method using PAH incurred seafood to test Gulf seafood for PAHs. We discovered that the PAHs in the seafood were subject to bacterial degradation down to a temperature of -70 degrees. Tough little buggers.
Bottom line, if PAHs are degrading in a sealed container of ethyl acetate it's either UV light or enzymes.