5 Replies Latest reply on Oct 5, 2017 6:32 AM by james_jenkins

    5975C GC/MS 219 ION HIGH

    elisteve

      After cleaning the source on a 5975C GC/MS and performing atune, the 219 ion is high, roughly equal to the 69 ion, and sometimes greater. The response of 69 is normal (219 is high, 69 is not low). This instrument is used for volatiles analysis and now will not pass the required bromofluorobenzene tuning criteria, since the 173-177 bfb ions are too high relative to the bfb 95 base ion. 219 cannot be lowered enough through manual tuning. The source, quad and transfer line are at the proper temperatures. Any solution to this? Try re-cleaning?

        • Re: 5975C GC/MS 219 ION HIGH
          ryan_ohearn

          Are you using the BFB Autotune or the BFB Tune?  Sometimes one works better than the other.

          You can also try switching filaments or replacing the filaments and repeller insulators (G1099-20133) and the lens insulator (G3170-20530).

           

            • Re: 5975C GC/MS 219 ION HIGH
              elisteve

              We normally use BFB Autotune. BFB Target Tune also fails with the default settings. The filaments are both new and both act the same. When I cleaned the source I found the lens insulator was cracked so that was replaced. Dynamically ramping the entrance lens voltage and manually setting it to a lower than normal value at ion 219 brings it down. BFB Target tune also ramps the entrance lens and you can manually modify the voltages that result. We've never had to do this before so it seems there is something wrong?

                • Re: 5975C GC/MS 219 ION HIGH
                  ryan_ohearn

                  Sometimes having the 219 higher than 69 happened a lot on the 5973, haven't really seen it much on the 5975/5977 due to different detector back end.  You could try re-cleaning and verifying everything, maybe also squeeze the lens assembly and the source body together when putting back together and tightening the gold screw since the source body is the only electrical connection to the drawout plate and cylinder.  You can use the link below to a cleaning document that has a lot of useful details.

                  How to clean an Agilent GCMS HES Ion Source