[Jespair (OP)]

Hi there.

I need to sample large amounts of rainwater at once, using a quite big funnel made out of stainless steel (~70cm entry diameter). I will then have the sample analyzed for many different pesticides and nitrophenols ASAP. The sample bottle is made from glass, delivered by the company doing the analysis.

My concern is about adsorption of potential analytes to the steel funnel while the water runs through. From what I can read, even very fast adsorption usually takes around two minutes to reach equlibrium, and water would run through much faster than that (though maintaining close contact to the sides all the time, so it would not be limited by diffusion).

To make sure adsorption is out of the question, I am considering treating the funnel with a layer of PTFE/teflon using a commercial spray, and I can't see how PTFE or any of the solvents or complementary chemicals in this would mess up the analysis. PTFE would solve all my problems with adsorption. Do any of you know if commerical teflon sprays for metal surfaces contain anything that could compromise such an analysis? I have read everything about the subject I can find.

- Thanks in advance :-)