Chromatography Forum

Hello
I m in charge of defining a new analytical labs with 18 GC scatered on 2 floors (6 labs)
I would like to know an overall gas consumption per GC (Agilent 6890) during a day, GC are used on a 24 hours basis, 5 days a week,

I have to estimate number of gas cylinders we need ?

when you dont use the GC on week end for example, do you let a gas flow of 10 % (stand by mode) or do you stop GC?

Have a nice day

I leave the GC with normal flow through the column and a small split (35:1) to avoid having air enter the column through the split vent for standby condition. Thus i use up to 36 mL/min on a continuous basis. My GC runs are splitless, though. I change a carrier gas cylinder on my instruments about once every three to four months.

Air into GC columns can be a bad thing. For a FID, air, hydrogen, and make up gas can be turned off over a weekend.

Gas usage will increase as you run into the addition of other components, such as headspace analyzers and as the result of maintanace practices (or poor maintanance practices). Faiure to change a septum in a timely manner can add significnatly to gas use.

You'll need to do a survey of the instruments. Note the column flows, split flow and makeup flow (of course, you need to know what you're using for each He, H2, etc). Then you can do the math, you'll need to gas volume/pressure for the cylinders (gas supplier website). Once you have this, then you can evaluate whether you need to make changes in the gas saver options for each instrument.

Naili,

larkl is right, do a survey. Not hard to do, having just done one for a lab. The bigger issue, I should think, is the other gases, specifically hydrogen and fuel air and compressed air. By the way, I recommend never turning off the carrier although you can take it to very low levels with gas-saver options.

Best regards.

Hello
thank you very much for your valuable answers,
best regards