Chromatography Forum

Hi there,

I was wondering if anyone could give me a detailed method for cleaning a "dirty" solution I have. I am investigating poly aromatic hydrocarbons in marine sediment. I have extracted the PAHs from the sediment using accelerated solvent extraction (ASE). I then used a turbo vap to concentrate my solutions, ready for injection into the GC-FID. However my supervisor said I need to perform some sort of chromotopgraphy on my "dirtiest" samples before I can inject them because they would get stuck on the column otherwise and clog the machine. One person suggested packing a heated pipette with silica gel and aliminium oxide and drawing the solution up into that. However he was not able to provide me with a detailed method and I have yet to find one in the literature either. If someone could direct me towards similar studies with methods detailing this process, I would be very grateful. Alternatively if you know a method you have used yourself that would be very helpful too.

Cheers,

Matt

Although most people seem to try avoiding it, GPC is the most thorough way to get good cleanup on dirty samples. Take a look at EPA Method 3640a.:

http://www.epa.gov/osw/hazard/testmetho ... /3640a.pdf

As previously mentioned, GPC is a great way to clean up dirty samples. It is also possible to add some adsorbants to the outlet end of the ASE cell and perform clean up simultaneously with extraction. The amount and types differ depending on the sample, analytes, and interfering compounds. There is additional information on the Dionex web site; look at technical notes (TN) 209 and 210. Alumina works well to remove lipids from marine samples. If the problem is sulfur, it is best to remove it post extraction using freshly activated copper or sulfuric acid (these procedures are described in the EPA method).
Some literature references are available that may help:
Annekatrin Dreyer and Michael Radke, Intern. J. Environ. Anal. Chem. Vol 85. No 7. 15 June 2005, 423-432.
M.C. Graham, R.Allan, J.G. Farmer, Science of the Total Environment. 360(2006) 81-89.
P. Canosa, et.al., J Chromatog. A, 1161 (2007), 105-112.

AOAC is currently validating a method for the extraction and analysis of PAHs from seafood. This should also work well for sediments. Send me an email and I will send you a copy of the method.

Don

dshelly@unitedchem.com