[cyrosceals]

I know about studied collecting hydrogen (over water etc), but how do you measure the EXACT volume of hydrogen collected evolved over for example 1 day when carbon dioxide and hydrogen is produced together from an organism ? The answer derived from the method must be extremely accurate (high tech computers and machines are ok) as long as it is exact. Can anyone just give me an experimental setup about it?

[Arkcon]

Some sort of chemical reaction, between the collected gas, that only reacts with CO2 or hydrogen, is one answer.  For example, bubbling the CO2 into a solution of limewater, or through a column of solid NaOH, is one option.  Or you can use the reducing power of hydrogen, passing the gas through a tube over a boat of heated metal oxide. Or even cryonics, passing the gas through a cold finger in a liquid nitrogen bath.  Very good accuracy may be a problem based on your engineering and technical level.  There are other problems, how pure the output of a biological system is -- are you getting no other gases, not even moisture, from your system?  Another option, is to get the entire volume sampled, and measuring it for total volume, then just take a small portion of it, sampled at the end, or in small amounts over the day, and run through a gas chromatograph.

[Borek]

How exact is exact? Even collecting over NaOH solution could be precise enough if you correct for air pressure, hydrostatic pressure and water partial pressure over solution.

[ARGOS++]

Dear Cryoseals;

Are you able to spend some information about?

• How large (m³) is your Experiment?
• How large (m³) is your Sampling Room (SR)?
• Do you already “know” how homogeneous could/will your SR be?
• What other kind of gases, except H₂O, CO₂, and N₂, you except, will influence?
• Do you know other important things about your Experiment?

Common for such Multi-Gas Analyses is IR-Spectroscopy with gas-specific Wavelengths and “Long Paths-Length Cells”, till several times 10 meters, and using MCA.

I hope I have been of help to you to get at least a start point.

Good Luck!
                    ARGOS⁺⁺

[Arkcon]

Common for such Multi-Gas Analyses is IR-Spectroscopy with gas-specific Wavelengths and “Long Paths-Length Cells”, till several times 10 meters, and using MCA.

 ARGOS⁺⁺

Aha.  So that what the 10 cm flow cell you mentioned here, http://www.chemicalforums.com/index.php?topic=23640.0 is for, very interesting.  You get a scooby snack.  (you were running a little  low, relative to me, a situation which should never be allowed to happen)

[ARGOS++]

Dear Arkcon;

Thank you!  for spending me sooo much “Goodies” of all kinds!

(But have you realised?:  This times they are Meters, not Centi-Meters!  How you will bet?)

Good Luck!
                    ARGOS⁺⁺

[ARGOS++]

Dear Cryoseals;

A certain time after having initialised the bet with Arkcon for the longest Cell Path, I realised, that it would be better to inform you, that:   

–    “Long PathsLength Cells”, till several times 10 meters – 

only mean their “Optical Pathlength” and not their physical size/properties.

For Info “How they work” you may visit:   "Long Path Gas Cells”
And for a few of several kinds of realisation visit:    "LongPathGasCell.pdf ”

Sorry!, –  if I should have scared you!

Good Luck!
                    ARGOS⁺⁺

[cyrosceals]

Firstly about my experiment, I intend to use a culture of h2 producing bacts and mixed with glucose solution and collect hydrogen gas. Carbon dioxide gases are produced but other gases like water vapour. The other products produced by bacteria are acetate and butyrate.

Ahh, IR-Spectroscopy. My teacher told me something about it but didnt told me that it is related to gases. He only told us about determining the functional group.(Im still not so advanced yet but I have access to it)

Can you explain more about it and the experimental setup(like using it) and provide some procedures, im not sure about the quantity of gases but it should be around 50-200 cm3 for 2hrs....

[Borek]

How precisely do you have to measure amount of evolving gas? Are you interested in hydrogen amount only or in exact composition of other gases as well?

[cyrosceals]

Hydrogen only. But others are welcomed as well if it doesnt hinder results. Im not sure how precise, but the most accurate method to measure the gas.(I even dont know how precise the IRS is)

[Arkcon]

As the fermentation proceeds, the distribution of gases will change, do you need to catch all gases from start to finish, to accurately quantitate hydrogen, of are you interested in samples at time points, perhaps with the intention of throwing out lag phase, and using just log or stationary phase?  A GC or FTIR may be your best bet to get a quick read of the sample, so you can get you answer before the hydrogen diffuses out of even the best sealed collection vessel.

[ARGOS++]

Dear Cryoseals;

With not too bad FTIR-Spectrometers and such “LPGC”’s you can easily reach for usual Gases the Level of a few ppm’s or even sub-ppm’s with a accuracy better then 1 – 5 %_rel.

I don’t know exactly the situation for H₂, because I never did it myself.

So I’m also not able to give you “full” advice, if it would be better for you to use the “Far-IR” or the other End of the IR scale, or move even more to shorter wavelength for H₂, because I thought already and the Statement in the 1. Attachment tells it you.
It is also fact, that at the moment I don’t have access to all the relevant and exact data.

But the following page maybe at least a Hint for the “Far”-end of the IR:   "NASA Reports IR: H2 N2 ”

For how you would do “best” design the analytical part of your experiment depends quite strong on your experiment and its size self, like:

•   Is your Experiment an open or closed System?
•   How large (Liters) is the gas room you have to control/to measure?
•   Is it allowed to circulate your gas mixture through the cell, or should you incorporate your “plant” into the Cell, because the experimental size?
•   And so on, and so on.

You may see: I know much too less about your experimental design, and so  –  only:
I hope I have been of help to you.

Good Luck!
                    ARGOS⁺⁺