Chromatography Forum

My laboratory is getting into Solid semivolatile analysis. Our problem is with extraction. We are currently performing extraction of BNA compounds via ultra sonication as we perform similar extractions for Pesticide and PCB. We get excellent recovery and reproducability for pesticide and PCB, but is usually poor and very incosistent for our BNA's.
We then tried BNA extraction via Soxhlate using 1:1 Acetone/CH2CL2. Recovery for soxhlate technique is good but only when the extractor turns over. However they rarely turn ove by themselves. As a result, recovery is poor. I'm looking for opinions on these techniques and others.[/quote]

I believe the soxhlet should be cycling regularly in order to achieve the best extraction. If it wasn't designed to cycle, the overflow tubing would be a little bigger. Sometimes it takes trial and error in order to get them to cycle when they are full. Positioning them so they kind of lean towards the spout is one way. Another is to give them a little shake when they get stuck, and check up on them every 20-30 minutes. Also, you may be able to have someone handy in glass blowing to get them modified better for you.