Chromatography Forum

I have a 5973 that is giving me fits.

I am running method 8260 using a 5890/5973 GCMS with an Archon autosampler and OI Eclipse 4660 P/T.

A curve was ran and passed fine, but when standards are ran the next day the internal standards are all out of whack. Part of them are almost failing high and one of them is almost failing low. I noticed that the one failing low uses a small mass as the main ion and the other three use a much larger ion as the main ion. I checked the BFB tune before the curve and then on the next day's standards and noticed that the 50 ion was smaller on the second day and the 174 ion was larger on the second day.

My question is:
Could it be possible that the instrument is losing the tune and shifting enough to throw off the internal standards and make the standards fail? If so does anyone have any suggestions?

Omaejel,

Start with another source from an instrument that is working fine. This will take both instruments down for a day but it is probably easier than trying to solve this piecemeal. If that solves the problem, clean the source thoroughly and if that does not work start replacing source parts. The repeller and ion focus specifically come to mind.

If that does not solve the problem, I would dip the quads (and keep the good source in the instrument.)

Best regards.

Thank-you for the input.

I can't take down another instrument at the moment because we are busy here at my lab.

I did however clean the source and noticed that the repeller edges looked rounded a bit. I guess the analyst has not been doing a wonderful job of cleaning it and has rounded them off with the sandpaper. I went ahead and replaced it. Will post an update soon.