Chromatography Forum

I need some help as I am new at troubleshooting and fixing MS problems. I am working with a new 5975C connected to an Entech cryo concentrator. The instrument has only been running for about a month, with most of the samples being either standards or blanks. Some fairly high-level samples have been analyzed and have saturated the detector, but not many. The samples are air samples in tedlar bags or 6L Summa canisters.

Yesterday my TO-15 continuing calibration curve would not pass. The ISTD and target responses were on a steady decline, so I bumped up the multiplier voltage a little from 965 to 988 and then reanalyzed the BFB standard four times overnight to see if the detector would settle down. None of the BFB tunes passed. All failed with the 75 ion rel abn too high in relation to 95 (~70%).

I performed an autotune followed by a BFB dynamic target tune. The report didn't show anything immediately unusual, so I analyzed another BFB sample. Again the BFB tune didn't pass for the 75 ion. I did the ramp for the repeller, and got what you see below. I'm guessing that is not what it is supposed to look like. This would lead me to think the repeller is dirty. Is this the case?

edit - it might have helped if I had the PFTBA open! Below looks a little better, but is the 69 ramp supposed to have 2 peaks?

Using the procedure outlined in this white paper

http://www.chem.agilent.com/en-US/Suppo ... 01323.aspx

I was able to get the tune to pass. I do need to find out from Agilent whether calibrating the mass axis for a 5975C is the same as adjusting the ion abundances as found in the Calibrate menu for prior models.