Chromatography Forum

Hi everybody,

Some of my recent samples are producing no chromatogram signal or a tiny amount of noise with no analyte peak. The problem is intermittent; sometimes my analyte peak shows and sometimes not. The MS voltage always turns on after the solvent delay and I've tried switching filaments with no success. I am using an HP6890GC/5971MS w/ HP7673 autosampler. I've monitored the autosampler and it appears to be working normally.

Thanks for your help,
Pat

I assume you are using an internal standard. Is it showing?

(And when is the last time you changed the septum?)

Assuming that the apperance of the internal standard is variable, I would suggest taking a standard and making multiple injections. If the standard mixture shows up well across multiple injections, look at the samples. If not, look at the instrument.

Turns out I thought the septum was in much better condition than it was. I replaced it, but still same problem so I changed the syringe. This looks to have solved it...must have been clogged w/ septum debris as the septum was badly cored. At first I was preoccupied with the possiblility that this was a mass spec problem and overlooked the simpler possibilities.

Happy chromatography everybody