GC-microECD analysis question

Hello All,

My lab has been trying to analyze fluorinated compounds in solvent on GC-uECD for a few weeks now and have noticed that the signal is very low compared to chlorine/bromine. I know that is to be expected, but it is so low sensitivity that it will be hard to analzye at any lower concentration. (Which will be necessary)

I am wondering if anyone out there has done work with fluorinated compounds on GC-ECD and has any advice. (Or knows whether or not this is feasible).

Thank you!

Madison Malone

  • Hi Madison,

    that is unfortunately true. Compared to chlorobenzene as reference fluoro-compounds range from 0.01 to 10 times the response, thus not very big, whereas chloro-, bromo- or iodo-compounds go up to 10000 times the response. If you have very low concentrations (and nothing very big in the mix) a PD-HID might give you better results, but it's easily overloaded and you might need some switching techniques.



  • Makeup gas and flow? I'll run 20-60 mL/min, dropping makeup gas flow will boost signal since it's in the analyzer longer. Biggest boost I've seen is from switching off argon/methane to nitrogen for makeup gas. As for the front end you can run splitless/pulsed splitless if you aren't already and increase injection volume if your liner can handle it.

  • The makeup gas is high purity N2 and the flow is 30mL/min.

    Unfortunately, I have tried both forms of S/SL (with/without a pulse) with no success. We have injected low (~5ng) and high concentrations (64ug) on each injection type with minimal change, so unfortunately, it does not look concentration dependent.

    Thank you for your help. We may keep trying a few workarounds. If you have any other suggestions, please feel free to let me know.

  • Thank you for your response. Is there any literature I can see on your reference of chlorobenzene? Asking as I would like to learn some more about it. (It is odd to me that Agilent's manuals do say that poly-fluorinated species see detects in the 10^7 Hz range - I have not seen that, and have asked Agilent application techs who have not seen it either)

    Sadly, I believe you may be correct - we got this instrument as hand-me-down, and were hoping to use it as screening tool, while our high-use instruments run our grant work. Fluorinated compounds are currently our target of interest, but we may adapt down the line if there is a need.

  • Then solid phase (micro) extraction could help to concentrate your samples and get a better signal.

  • When I need information about detectors I use the following books:

    • Raymond P. W. Scott "Chromatographic Detectors - Design, Function, and Operation", Chromatographic Science Series Volume 73, Marcel Dekker, New York (1996). ISBN 0-8247-9779-5.
    • Raymond Annino, Richard Villalobos "Process Gas Chromatography - Fundamentals and Applications", Instrument Society of America (1992), ISBN 1-55617-272-9.

    For the ECD there was also a separate Volume from J. Chromatogr. A, full of useful articles, (gave it to someone and never got it back :-( )

    Here are some pages from a presentation of mine.

    I will add a Wiki article here in the Community in the Consumables area about the ECD, so please check every once in a while.


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