>chris_blencowe at my-deja.com> wrote
>: I am having trouble with extracting the phenanthrene from the soil I am
>: using in order to assess its degradation .....
Efficient extraction from a complex matrix can be difficult, and
soil is complex. Your post sounds like you have done some reading
on the topic, but I checked the AOAC manual for analysis of polycyclic
aromatics from meat, and that method says boil in alcoholic KOH. So
a process that harsh apparently works. Phenanthrene is tough, and
you can beat on it a lot without decomposition. Unless I could find
something better, I'd try boiling soil in alcoholic KOH. The method
says filter, remove the solvent, but do NOT allow to go to dryness, as
loss can occur. If you have been oven drying your soil to remove
water then it would seem that loss of phenanthrene could occur. Have
you, for example, put a measured amount of phenanthrene into a soil
substitute, such as peat moss or beach sand, done the processing
steps, and then recovered phenanthrene? If your methods doesn't
work on sand, it's not likely that it will work on soil. I would
also pour my digested soil into a column, and elute with fresh solvent
from the top down, like a gravity flow column. Much more efficient
than steeping and stirring. Though phenanthrene is a very nonpolar
substance, I would still think that a solvent more polar then hexane
would be a more efficient solvent for extraction. At the very least,
use toluene, or a hexane plus cosolvent combination. I haven't looked
yet, but I would think that in the literature there should be several
papers on the extraction and analysis of such nonpolar molecules from
soils around contaminated sites, like oil refineries, chemical plants,
etc. In the US we rely on the EPA (environmental protection agency)
to develop such methods of analysis. You might want to visit the EPA
website. I would also be quite amazed if someone has not already
published on microbial degradation of phenanthrene. If they have a
good method, then use it. Don't waste you're time reinventing the
wheel. Read the literature and build on top of what has been done
before. Best of luck with your project.
Tom McCloud
SAIC/Frederick Cancer Research
Frederick, MD
I do not have access to working Soxhlet Extraction
>: Apparatus nor the equipment to conduct an extraction using
>: Supercritical Carbon Dioxide, which seem to be the most popular
>: methods. Instead I have been using a simple hexane extraction
>: in order to try to recover the phenanthrene but this does not seem to
>: be effective. I have tried drying the soil samples to remove
>: the water content and increasing the amount of agitation the samples
>: undergo.
>:>: Are the any further suggestions to improve this method and/or do you
>: know of any other robust and yet simple methods for the
>: recovery of phenanthrene from soil?
>
