Chromatography Forum

I am using an Agilent 7890A equipped with a micro-ECD (among other detectors) to analyze gas samples for nitrous oxide (N2O) concentrations - however, the sample matrix also includes acetylene (C2H2) .

I have read (and been told by colleagues) over and over that C2H2 can poison the ECD, so it's important to vent it before it reaches the detector. I've gone to great lengths to set up my GC so the C2H2 can be vented, only for an Agilent technician to ask me, "Why exactly do you need to vent C2H2? It shouldn't harm the ECD...".

Does C2H2 in fact poison the ECD? If so, how?

Thanks for the help!
Greenhouse Gas Girl

I can't see why it would poison it. Unless it "chars" under inert conditions and heat. Then maybe it could blacken the surfaces inside the ECD. This is just my speculation however. I have never heard or observed this.

I guess the verdict is still out. I haven't had anyone provide me with a definitive answer for if and why C2H2 is bad for ECDs. But the warning that it does is published in Methods sections over and over:

Mendoza Y, Goodwin KD, and Happell JD. 2011. Removal of atmospheric CCl4 by soil microbes. American Society for Microbiology.

Ogilvie B, Nedwell DB, Harrison RM, et al. 1997. High nitrate, muddy estuaries as nitrogen sinks: the nitrogen budget of the River Colne estuary (United Kingdom). Mar Ecol Prog Ser 150: 217-28.

Fazeli-Matin S, Gordon AS, and Marshall HG. 1991. Sediment denitrification potential in the Elizabeth River, Virginia. Va J Sci 42: 113-22.

Miller LG, Oremland RS, and Paulsen S. 1986. Measurement of nitrous oxide reductase activity in aquatic sediments. Appl Environ Microbiol 51: 18-24.

I put this question to one of our R&D guys, and here is the reply that I got.

" From my quick look, it appears that Ni is a good catalyst for making cyclic unsaturated compounds from acetylene. This is likely the source of the concern and if the acetylene coordinates to the Ni, you may decrease the electron flux or make unstable stuff on the surface of the cell. With my lack of direct knowledge, I would avoid using it."

Gasman

Thanks for the response, Gasman! I'm thrilled to finally have an answer!

Best,
GHGirl