9 Replies Latest reply on Feb 7, 2019 7:09 AM by hennindm

    New to GC FID

    revathy

      Hi

       

      I am new to GC Method development phase. We are having GC 7820 A with FID detector. Currently I am developing a method for industrial solvents. When I run a blank (THF), I got a very unusual spikes in the chromatogram as seen below. I have changed the inlet, septum and checked the gold seal which looks good and trimmed the column in the inlet end. Any suggestion would be of great help

       

      Thanks

       

      Revathy

        • Re: New to GC FID
          james_jenkins

          Hi Revathy,

          These are electronic noise spikes. Typically when you see a sharp spike with no area under the peak/ spike this is from the fid or fid electronics. The fid collector has a spring connection for the signal to the electrometer and dirt or corrosion can cause spikes like you are seeing. I would suggest taking the FID apart and cleaning the collector assy and changing the jet as a first step. I have attached a section from the 7890 manual that covers FID maintenance. The procedures in the manual apply to other Agilent GC models as well as the FID assemblies are all similar. I hope this helps.

          Regards

          James

          • Re: New to GC FID
            dmarchini

            Hello, spikes like that are usually coming from the detector, you can try what happen if you "tic" with a screw on a fid jokin, don't do that

             

            In my lab we don't bother about noise like the one you show us in the picture, cause we set the signal windows between 0 and 50.

            But if you need super flat baseline without spikes like that I suggest you to perform manteinance on the fid, especially installing the column perfectly.

             

            Apart from the detector spikes, and to be picky, I would check also the gas purity and the inline carrier filters, because a 10 pA baseline is pretty high for our standard (we have a 3/4 pA baseline at oven 70°C)

              • Re: New to GC FID
                revathy

                Hi Dmarchini

                Thanks you for pointing it out about 10pA baseline.  The fig. which I sent it is at the end of the run(before maintainance).  Now my base line at the start of the run is 5.1 at 70°C and by the time it reaches max temp of about 300°C the pA is about 6 (is that good enough) and it stay stables there until the run finishes (21 min run).  What you mean is yours in <1pA(3/4) is that right.   We have new inline carrier filters so i guess that is not the problem.  Let me know if this baseline is good enough.  Thank you for your time.

              • Re: New to GC FID
                hennindm

                In addition to dirty detector, the spikes can be due to a column clip, silica particles flying through. This typically disappears after a good bake out.