Low recoveries for EPA Method 508

[mdewald]

I'm having recovery issues with EPA Method 508. We use the mechanical method for the liquid-liquid. None of the GC parameters have changed from the last time things were run but we have always been on the lower end of passing a PT. Currently we are using Teflon TCLP bottles for the tumbling and Teflon Sep. funnels. If anyone has ANY suggestions on improving either the extraction end or the GC method please let me know. Thanks

[deanne0711]

Hello - I had a quick look at EPA 508 - it looks similar to the 8081 and 8082 methods.

I assume you are extracting with DCM and then solvent exchanging into hexane for ECD analysis or just running in DCM on an MS???

At any rate, my last lab that I worked with experimented with a tumbler style mechanical liquid-liquid extraction and found our recoveries dropped significantly. The tumbler just wasn't rigorous enough when it came to performing the extractions - so we continued to extract by hand. It took longer but our results were much better. You may want to try a few by hand to see if this could be the case for your lab.
Also, if you concentrate your extract too quickly or at too high a temperature, you will lose your analytes. Try dropping the concentration temp to 35-40 Celsius.
What type of concentrator do you use?

[mdewald]

We are exchanging into MTBE and running on an ECD. We use a horizon xcelvap for our concentrations. What were you using at the previous lab?