GC/MS Loss of signal over time

Koos:

150,000 counts seems very low in my experience.

About source cleaning: The manuals should give instructions on how to clean the source. We have a 5975 which hasn't needed cleaning and 2 5973s that I have cleaned many times over the last 20 years. I have no experience with the 5977. Briefly, you have to break vacuum, remove the source, disassemble it, clean dirty parts with green sand paper and/or aluminum oxide, sonicate in solvents, reassemble, reattach and pump down. I assume that all 5977 documentation is on line and there are probably source cleaning videos available if you search for them. The whole process usually takes 3-4 hours. I just watched an Agilent webinar (Simple Strategies for GC/MS Success ) that explains how to examine your autotune report to determine if it needs cleaning. If you can find the first autotune report printed at installation, you can get a good idea what it should look like. I think you can view the webinar through these links:

The View Recording button will allow you to sign-in and view the recording.
https://agilenteseminar.webex.com/agilenteseminar/lsr.php?RCID=110b45c8ad3ae6d80560abcbd24efd0d

  If you wish to download a PDF copy of the presentation, please visit:
www.agilent.com/cs/library/eseminars/public/AFO_Simple_Strategies_for_GCMS_04112018.pdf

This was sent after I attended the free webinar, but I think it is OK to share it. I recommend Agilent's webinars on basic GC, LC and MS procedures.

I tried to bake out the glycerin contamination when it happened on our 5973. No luck. You are probably "polluting" the source. The autotune sets the electron multiplier voltage to achieve maximum sensitivity and as the source gets dirtier, that voltage will probably increase. If you keep your old reports, you can see it go up. Weekly autotunes are now considered a little too often but I started out on a 5970 that was tuned every day.

Koos:

150,000 counts seems very low in my experience.

About source cleaning: The manuals should give instructions on how to clean the source. We have a 5975 which hasn't needed cleaning and 2 5973s that I have cleaned many times over the last 20 years. I have no experience with the 5977. Briefly, you have to break vacuum, remove the source, disassemble it, clean dirty parts with green sand paper and/or aluminum oxide, sonicate in solvents, reassemble, reattach and pump down. I assume that all 5977 documentation is on line and there are probably source cleaning videos available if you search for them. The whole process usually takes 3-4 hours. I just watched an Agilent webinar (Simple Strategies for GC/MS Success ) that explains how to examine your autotune report to determine if it needs cleaning. If you can find the first autotune report printed at installation, you can get a good idea what it should look like. I think you can view the webinar through these links:

The View Recording button will allow you to sign-in and view the recording.
https://agilenteseminar.webex.com/agilenteseminar/lsr.php?RCID=110b45c8ad3ae6d80560abcbd24efd0d

  If you wish to download a PDF copy of the presentation, please visit:
www.agilent.com/cs/library/eseminars/public/AFO_Simple_Strategies_for_GCMS_04112018.pdf

This was sent after I attended the free webinar, but I think it is OK to share it. I recommend Agilent's webinars on basic GC, LC and MS procedures.

I tried to bake out the glycerin contamination when it happened on our 5973. No luck. You are probably "polluting" the source. The autotune sets the electron multiplier voltage to achieve maximum sensitivity and as the source gets dirtier, that voltage will probably increase. If you keep your old reports, you can see it go up. Weekly autotunes are now considered a little too often but I started out on a 5970 that was tuned every day.

Found all the other instruction manuals and first-ever tune. Thanks for the info Steven!