Chromatography Forum

hi all...hopefully someone can help us figure out what's wrong with a gc we use for epa 515.3 and 552.2. basically, it started with a snap crackle pop accompanied by an electrical smell immediately afterwards. there was nothing inside the panel indicating what happened visually but the resulting chromatography had peaks all over the place, especially in the final 30 minutes or so of each injection. because the ecd was nearing the end of it's lifetime, we swapped it out with another we had on hand in preparation. we observed no problems while it stabilized (signal down to ~13 the following day.) now our high calibration standard peaks are barely even visible for both methods. we double checked gas flows and repeated the general maintanence to rule out the easy and obvious but got the same results. we then borrowed an electrometer from a working 5890, which made no difference either. i don't know near as much about the 5890's inner workings as my supervisor, who has worked with 5890's off and on for 20 years and suspects the motherboard is the real culprit. i was hoping someone here could point us in the right direction if we are missing something as i am fairly fond of 5890's and would prefer to get this one fired back up if possible. thanks in advance for any welcome suggestions...

Oh man, I haven't used a 5890 in years. Hopefully the circuit boards aren't too different.
I am assuming the electrometer plugs into a smaller detector board, which plugs into the motherboard. If you are running dual ECDs for confirmation, try switching out your detector boards. If one of the boards is fried it could give you weak signal strength or none at all. Also, if the peaks are extremely skinny and both above and below the baseline, (almost like an EKG signal) that is electronic interference, and you should insulate your electrometer post. If your ECD has a thin wire with brass ends connecting the "chimney" to the electrometer, try switching that out too. One last thing: If your make up gas flow was not checked from the detector end (checked going in instead of coming out) you may have a leaky gas line. (Make up gas should exhibit a low exitation energy, allowing for an easy removal of electrons from the gas molecule.) If your gas isn't passing through the detector properly or your electron emitter or your anonde is faulty, there will be a loss of sensitivity.

Does your oven cool?
Sounds something like what happened here when we blew a triac. It's behind the back pannel near the main power board.

Call Alpha Omega!

Thanks to the suggestions! Turns out, it was a bad solenoid. After trying to frankenstein a working GC together, we actually witnessed it happen a second time (the smoking was coming from blown fuses.) We were able to put another solenoid on and now it works!