PAHs from Soil

Extracted soil spun down using a robotic centrifuge

I’ve been working on the extraction of PAHs from soils again this week. We have a fairly crude method whereby we extract 2 grams of soil in conjunction with 1g of copper. To the soil sample the GERSTEL Multi Purpose Sampler (MPS) adds 2ml of acetone and the soil/acetone slurry is mixed for 15 minutes in an agitator. Then 4ml of hexane is added and the mixture shaken again for 15 minutes. Finally 2ml of water is added to promote a phase separation and the mixture is shaken again for 5 minutes. Finally the vial is centrifuged for 5 minutes at 2500 rpm.

1ml of the hexane supernatant is then removed, spiked with deuterated internal standards and analysed using GC-MS.

Initial recovery data from spiked loam soil samples looks promising with samples spiked at 1ug/g displaying preliminary recoveries of 77 to 139 % with an average recovery of 97 %. I have a certified reference material on order and will be performing the extractions on this material to prove method robustness, and to determine recoveries from a real material.