Poor aldrin recovery at low level EPA 508.1

[shan820]

I found an old post with a question very similar to mine, so I suspect I am not the only one with this issue, but that discussion was closed so I thought I would start up a new one.

My lab has been experiencing erratic recoveries for aldrin in spiked water samples. Both in liquid-liquid and solid phase extractions. I am trying to transfer our current L-L method to the SPE by 508.1 using a Horizon 4790 extractor and C18 speeddisks. And I would really love to resolve this issue.

Everything looks great except for the aldrin when I spike at 0.05 ppm. 0.1 ppm is fine. Analysis by GC-ECD.

Anyone have experience with this and/or have any solutions for improvement? TIA!

[fsistere]

Hi
If you analize drinking water, the Cl2 react with Aldrin very fast. You need to add sodium tiosulfate to neutralize Cl2 before spike Aldrin.

[shan820]

I will be analyzing drinking water, but right now I am still just spiking DI for method development. I will try your suggestion, thanks!

[shan820]

Well, I added sodium sulfite, rather than thiosulafte, but it did not help. Not that I expected it to make a difference with the DI spikes, but I figured it would be good to try, and also I adjusted pH < 2, as per the method.

I still can only recover 14% aldrin at 0.05 ug/L. All 20+ other pesticides recover > 80%!