Chromatography Forum

Hey, maybe someone can help me with my GC/FID situation. I have 3 GC/FID 6890 instruments that have zero air generator attracted to all 3 of them. Every few months I would have to replace the jet on one of the GC, which is very unusual to me but, once that happens for some reason all 3 GC/FID being affected by it. I would give me shark fin shape peaks and once I replace the bad jet, all 3 GC/FID would work fine for another few months. any suggestions??or ideas that might help?

... I would give me shark fin shape peaks and once I replace the bad jet, all 3 GC/FID would work fine for another few months. any suggestions??or ideas that might help?

Karol,
shark fin shape peaks (you mean fronting peaks ?) are symptoms of column overloading rather than clogged jet orifice

PS - I hope you have a moisture trap between zero air generator and GC - not digging into details if there is no moisture trap zero air generator may kill EPC.

dblux_,
thanks for your feedback, peaks are happening when the jet is trying to light itself and they look like shark fin peaks but, its happening to all 3 GC's when only one GC jet is popping

Could the zero air generator not have enough capacity and the sudden change in flow when one lights be causing a drop in flow across all the instrument due to low line pressure?

Do you have a pressure gauge on the air line you can monitor as the instrument lights?

dblux_,
thanks for your feedback, peaks are happening when the jet is trying to light itself and they look like shark fin peaks but, its happening to all 3 GC's when only one GC jet is popping

I see. What is lit offset setting in 6890 GC and what are the flows of hydrogen, air and makeup gas ?

Could the zero air generator not have enough capacity and the sudden change in flow when one lights be causing a drop in flow across all the instrument due to low line pressure?

Do you have a pressure gauge on the air line you can monitor as the instrument lights?

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Do you have a pressure gauge on the air line you can monitor as the instrument lights?

In fact 6890 itself has flow meter and any drop of air pressure resulting in drop of flow may be read from the GC display. Besides flow drop brings on a notice on display about insufficient air flow.

Karol413,

Not to sound like a broken record, but are you replacing jets because your 6890 is not lighting? If so, I would like to recommend you check out the FIDIGbolt which will basically guarantee that you Agilent FID will light EVERY single time you ask it too. If it does not light with a FIDIGbolt you have bigger issues with your detector.

It works so well I am recommending people turn off their Agilent FID's when not in use to save money on hydrogen and air costs.

Best regards,

AICMM