Chromatography Forum

For those of you who are using Hydrogen as the carrier gas already. What have you done with regards to the split vent output of your instruments?

I ask because we have a lab containing GC's , HPLCs and our ICP unit and I'm a bit wary of pumping hydrogen into the lab area from multiple GC units.

It is good to transfer the vent line to a hood or to a window in the building. Hydrogen gas will RISE and can collect where it may be trapped. When it is trapped it is liable to explosion due to static electricity, or any source of ignition.

One only has to see the nuclear power plants blowing up in Japan after the earthquake to see the force that can be unleashed when trapped hydrogen mixed with air ignites when it contacts a source of ignition.

Most building are not sealed that well, but I would take no chances unless you know your heating and cooling structure of your building does exchange the air with outside air at a fairly rapid rate.

Would you release natural gas into a lab without venting it outside?

Vent to a location outside the building.

Rod

You're right to be wary, considering that H2 mixtures are explosive over a range of something like 4-70% with oxygen. On the other hand, with the safety controls already installed in modern GCs it is certainly possible to do safely. I recommend reading over these articles:

http://www.restek.com/Technical-Resourc ... orial_A016

http://chromatographyonline.findanalyti ... ?id=653133

http://chromatographyonline.findanalyti ... ail/709613

If you're going to use tanks I would keep them in a secure area where unauthorized people cant go monkeying around with the tanks or regulators. I would recommend generators over tanks, although you must be aware that generators must be maintained and are not "set it and forget it" otherwise you can have problems where wet hydrogen can contaminate the gas lines and ruin expensive electronic pressure controllers. If you are diligent about checking water levels and monitoring your filters and traps you only need to spend a minute or two each day checking to make sure things are running OK.

As far as your split vent outputs, you can either install a vent that just sits above the output and sucks away any H2 or sample OR you can directly attach something to the 1/8th in. swagelok fitting to vent to a safe area.

Hi,

If we are using hydrogen as carrier gas, does the hydrogen release to the air from the FID detector? Is placing a exhaust vent on top of the FID detector essential?

Thank you

In an FID detector the hydrogen is burned in the flame. So as long as the flame is lit, there is no hydrogen escaping into the room. If the flame is out and the gas flow is on, hydrogen is released. (Modern instruments will turn of hydrogen if the flame is not sustained.) In labs I have been in, hydrogen diffuses so quickly and the air turnover in the lab is sufficient that there is no need for concern over accumulation of hazardous levels of hydrogen from the FID or septum purge - even on older instruments.

There was a time that one would set flows with a flow meter, and after getting them all adjusted and gasses turned on, one would press the igniter button. There would be a pop and the flame would be lit. Ocasionally the flame would not light - which was determined by lack of signal and lack of fogging a mirror (all of which would take several minutes to check - with gas flowing) and the next step would be to push the ignitor button to see if the flame would light and stay lit. Pressing the button would produce a pop from down in the instrument - not a blast, knocking small tools from the top of the GC or such. The gas stream leaving the FID mixed with the air in the room so quickly that the only hydrogen igniting was that contained in the FID or very close by the exit from the FID.

If you place an exhaust vent over the FID,you are introducing an air current that has the potential to affect the flame. I would suggest against that unless you are working with compunds that are so toxic that you would have a concern about what residual material might survive the flame and go free in the room.

The split vent, which may deliver considerably more hydrogen into the room (depending on settings), a different story, which Rod addressed above.

If doing split injection chromatography then very little material enters the flame, even the solvent itself, and most air exchange conditions meet any safety concerns. However, if you have splitless injection using chlorinated solvents like DCM, then there is a POSSIBILITY of several GCs producing enough toxic gases in the flames in an low exchange rate area where it MIGHT be of a health or safety concern.

In a very small room I once had 3GCs running packed columns using chlorinated solvents and silylating reagents and we thought it best to put small funnel shaped vents ABOVE the GC detector areas to expedite the removal of combustion products from the FIDs. But we had pregnant chemists and legal issues which were so costly to contest in court, it was decided it was much cheaper and safer to spend a few hundred dollars and make the employee feel better and well as work safer in a potentially dangerous situation.

Sometimes a little money goes a long way in increasing morale and productivity. The benefit/cost ratio being so high, it was decidedly foolish to do anything else.

best wishes,

Rod

Rod's mention of chlorinated solvents does bring back memories of injections of chloroform on a packed column, through a FID. I recall seeing a swirl of soot ocasionally when the chloroform reached the detector. We never gave it a second thought - although, perhaps we should have.