4 Replies Latest reply on Mar 14, 2018 12:03 PM by cberdugo

    FID SPIKES

    cberdugo

      Hi all,

      I am using a GC 6890 with split/splitless inlet to analyse reaction products. However, a problem has recently happened when the GC is running.

       

      I have noticed the appearance of spikes in the baseline of the FID detector. The spikes appear occasionally. (See pictures below). The pictures attached correspond to the same experiment. As you can see the spikes occur before or even at the retention times where the analytes elute (between 13 and 15 min).

       

      Spike in chromatogram5.png

      Spike in chromatogram3.png

      Spike in chromatogram2.png

      Spike in chromatogram 6.png

      Spike in chromatogram 7.png

       

      I also noticed, that when I turned of the FID, the signal reading is not 0, but a value around 0.76 and keeps oscillating,

       

      s.png

      Closer look to the signal when FID is off:

      333.png

      Aside from this (and maybe related to) the peaks are eluting 1-1.5 minutes earlier for the FID.

       

      Any suggestions on what to look at?

      Regads,

        • Re: FID SPIKES
          james_jenkins

          Hi cberdugo,

          In looking at the data you sent, your signal and response is very low. Some of the peaks you are integrating are less than a pico amp in response. Working in this range will never yield an acceptable signal to noise ratio. What you are interpreting as spikes may just be normal baseline fluctuations. I would work at increasing response of your peaks of interest . If its a split method, decrease the split. I see nothing unusual here. The signal level with FID off is normal as well. If you want to respond with method parameters, the community may be able to make suggestions to improve the signal.

          Regards

          James

          • Re: FID SPIKES
            valentinrusu

            Following up on James' response, I would agree and also add that you might want to run the FID checkout sample. The purpose would be to see if the response you get, both in terms of peak shape and peak area, is comparable to the checkout chromatogram (usually this is included with the checkout sample, but should also be in your operation and installation manuals).

            • Re: FID SPIKES
              james_jenkins

              Hi cberdugo,

              Were you able to resolve the signal issues or have any additional information that others may benefit from, please come back to this post to provide an update.

              James

              • Re: FID SPIKES
                cberdugo

                I decrease the split ratio and the spikes were gone.

                Thanks,