what grade Nitrogen for FID makeup

[MSCHemist]

I am in the process of switching our Makeup gases from helium to nitrogen (FID, FPD, and ODP). We have been quoted for BIP (built in purifier) nitrogen at $300 a cylinder (we pay $550 for BIP helium). I am just going to use a hydrocarbon trap on it. Can I get away with a lower grade N2?

[chromatographer1]

Using the inferior grade of N2 opens up issues of greater noise and baselines drifting.

It may not be a problem.

But if it is , how would you know for certain?

Would you also use inferior grades of hydrogen for your fuel?

If you spent a whole day producing inferior work due to inferior gas, how much would that cost your lab?

Is it worth taking the chance? Life is a gamble. Proceed at your own risk.
But who wins if you are right? and who loses if you are wrong?

best wishes,

Rod

[Don_Hilton]

I learned from one vendor that research grade gas is tested from the filled cylinder; the less expensive ultra high purity is tested from the truck and cylinders are filled from it.

Having seen what some people do with gas cylinders, I'd rather have the filled cylinder tested...

[Peter Apps]

Bear in mind that what comes out of the cylinder is not what goes into the GC - there is a regulator and some pipes in between at the very minimum. I use 99.999% instrument grade nitrogen with a big carbon cartridge immediately upstream of each instrument.

Peter

[CE Instruments]

Just for make up gas ? Then a low grade will be fine, Just check the specs, you only need a low spec for Hydrocarbons (or add a trap) The tough bit about Nitrogen production is making it Oxygen, free not an issue for make up gas but would be for carrier.

[Johnny Rod]

I would also say standard cylinder nitrogen is fine with in-line traps for moisture, oxygen and HCs.

[MSCHemist]

I assume with an FID the only contminants that really matter are hydrocarbons as they generate a signal. A percent or two oxygen, argon, probably won't make a big differnece especially considering I have a 5890 FID and regulating the gas flows aren't very precise (regulators and flowmeter) plus the air is being supplied at (20% O2 at 400 ml/min) compared to the makeup at 30-40ml/min.

The ODP as long as I can't smell it it doesn't matter.

FPD I am not sure but it hasn't been used in years and I doubt it ever will be. We have a MSD.

[chromatographer1]

I think you have a clear picture of the situation.

Rod

[Yama001]

Those prices sound crazy - I am in New England; we pay 178.00 for UHP Helium and 78.00 for UHP Nitrogen. The UHP is 5 nines. We also use a technical grade Nitrogen for pressure driven stuff, it works fine as a make up gas though. I believe these are the 300 size tanks.

[MSCHemist]

I'm in Chicago we use Airgas. They charge $500 + tax $550 for Build in purifier grade helium, $300 for BIP nitrogen and I got a quote today for $220 for UHP Nitrogen one grade down from BIP. Is it just our location or our we getting gouged?

[Johnny Rod]

BIP means the cylinder has a purifying trap built into it? Not seen that before. Some people run "normal" analysis grade gases straight in (non-MS instruments), more often is to use these with traps like the Agilent Big Universal Trap or Chrompack cartridge jobbies. These last well past the one year they are specified for, I prefer Chrompack because they have indicators in them (the Agilent traps work just fine but they are a metal cylinder so you have to figure it out yourself, but you only have to buy one unit). look at it this way, do you pay for one set of traps that least for years, or buy a small one on each cylinder you buy? Take a look at costs of these if you want, payback may not be as long as you think.

For nitrogen as make-up we use standard oxy-free grade, no traps. We put a trap on the methaniser where it is used as carrier beacuse there must have been a sub-ppm trace of CO in it as we discovered during method validation. i can't speak for Airgas but I know where ours comes from.

[tiggeria]

We are paying $32 for a UHP nitrogen 291 ft3 tank. But we have special discount for contracted price, I can see we could have paid much more for non-contracted cylinder size and grades.

For that price, UHP grade is not a brainier.

[larkl]

We routinely use "plant" nitrogen for FID makeup. I'm in a manufacturing plant. this is cryogenic nitrogen, which is good quality. It is shared with the operating units, so there is some risk if contamination, primarily from a stuck or leaking check valve. Having said that, we don't have any issues (or none that we are aware of ). I have heard horror stories of labs seeing 2 foot high FID flames when the plant managed to get something like ethane or ethylene into the nitrogen. Scary.

[MSCHemist]

I use a cheap industrial grade nitrogen for blowing off solvent in one of my analyses but I figured even with a trap it might contain too much hydrocarbon to be useful. I think a regular high grade nitrogen should be ok.