wmbigham wrote:
We are having the same issue. Major loss of Anthracene, Benzo(a)pyrene and Perylene-d12. Driving me crazy. I have tried adding preservative (sodium sulfite) and altering the amount of 1:1 HCl to see if that makes a difference. It hasn't. Also, if I run the extract as soon as they are ready we get low recoveries but if we wait to run them the compounds disappear completely. If I rerun the extract several days in a row I can watch the recovery get lower each day for these compounds. I haven't tried to avoid light although our sample bottles and chromatography vials are all amber glass. We didn't used to have this problem and are now starting to see this happening in our 550.1 extracts too. I'm not sure what changed.
Wow! After 26 years of analyzing PAHs I thought I'd seen everything.
You have eliminated chlorine and pH. We can also rule out microbial activity.
That leaves: light, ozone, temperature (as a catalyst) and possibly particulates in the final extract. Since you run 550, which uses DCM, it would be hard to believe that PAHs would have a greater affinity for particulates than for the solvent. That leaves light, ozone and temperature. If there is any other way to breakdown PAHs, I suggest publishing.
I believe anthracene is the most susceptible to photo-oxidation.
If you can provide any other details it would be helpful.
Don