Chromatography Forum

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!

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.

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

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%!