Chromatography Forum

Hi, I have 5 varian 240 gcms, actually one is 4000, all ion trap, and one of them is killing me, i run opiates on it all day for quant, and it was running great, and then one day the peak heights started slipping and now the machine is sitting idle, i have cleaned and changed the trap, the source, the filament, the mutliplier, clipped and then changed the column, the liner, the septum, the syringe, it tunes, it runs, the peaks suck, i use to get mega counts now i get kilocounts, I have compared the method from the machine and pc next to it and made sure it was verbatim. what am I missing??????? I can take a sample inject it on the machine next to it and tadah great height, then put it on this machine and low peaks again. I am stumped and angry! any suggestions, my boss wants answers I have been looking all over the web for an answer, should I rule out inlet flashback, injection volume, hold time etc? should I just stick my head in the oven?

Paul

Hello.
You can not refuse to heroism, but heroism - is a fee for any errors.
You should gradually check every detail, first the system test mixture. After then check separately chromatograph and separately detector. And do not try to fix everything at once. As we say " if you should catch two birds (rabbits) in one time - you not catch bird (rabbit)"
Perhaps there were problems with the chromatographic column or chromatography, for example perforated septum or damaged capillary wall (nut septa). Perhaps there were spectrometr problems with the ionization /detection .
Now then what was the problem - do not know. Pray that everything was fine.
PS
I hope the after you repair does not remain "superfluous details".
Many years ago, was I problem "superfluous details"

Paul,

To determine wether the problem is mas spec or GC, how does the tune of the mass spec look, particularly intensity of the signal from the tuining compound? If the intensity of the tuining signal is weak, let's focus on the mass spec; if it is strong, let's focus on the GC.