Chromatography Forum

Hi, I am trying to extract POPs including PAHs from a sediment sample using ASE. The extraction works well, however when I am concentrating my extract a water layer forms . I am using DCM:Hex:Acetone in the ratio 2:1:1. Other solvents typically gave lower recoveries for my CRM (NIST1941B)

Any advice?

Thanks

R

Ruben,

You can incorporate a drying agent such as sodium sulphate or magnesium sulphate at one of 3 stages. Grind your sediment with it before adding to the ASE tube, add the agent to your ASE tube without grinding beforehand or dry your extract with the drying agent after extraction. Intimate mixing before extracting usually gives the best recoveries.

Rich

I am pretty sure that Magnesium sulphate is NOT RECOMMENDED for use in ASE as it may precipitate out in the lines. To remove water interferences, we use hydromatrix as the grinding material, and also use a small layer of mydromatrix at the bottom of the cell (before adding the sample). Alternatives include reducing/removing the acetone, or passing the final concentrated extract through a pipette containing sodium sulphate held in place using glass/cotton wool.
Hope this helps