We're using a TCD detector and I can measure quite small amounts, but I don't know about the economical aspect as I didn't order it ;)

I learned that with TCD we can measure above 100 ppm hydrogen, what was your concentration in ppm?

Can we measure hydrogen in the range of 5-100 ppm using TCD?

Yep, TCD would be the best option that springs to mind, you may want to use a carrier gas other than helium as helium and hydrogen have pretty similar thermal conductivity (give nitrogen a try.) http://hyperphysics.phy-astr.gsu.edu/hbase/tables/thrcn.html

TCD is linear from approximately 10^-9 g to 10^-3 g, so close to 1 ppm would be the cut off, but it should work.

Use TCD with nitrogen or argon as carrier gas. You can also adjust split ratio and volume of sampling loop.

I agree the TCD is the best choise.

Of course using Nitrogen as a carrier as Alex apointed.

micro TCD (I can't give you the brand for commercial reasons) is able to detect ppm of hydrogen (LOD on my instrument is about 1 ppm ) and a little more for oxygen (LOD 10 ppm) using Ar as carrier. We use it routinely. Many of other answers given before this refer to old instruments.

Respected Sir you can SRI Model 310C Gas Chromatograph

equipped with a Thermal Conductivity Detector

( TCD ) which can be used upto 10 ppm of H2

.

I use a micro-GC with a TCD detector and Argon as carrier gas and it works fine

For high sensitivity detection of H2, you can use the new barrier discharge detector from shimadzu. 100x more sensitive than TCD.

Definitely TCD is the best option. sensitivity depends on the GC model, column and carrier gas. in my experience Ar is best carrier for H2 sensitivity and you can detect in ppb levels too. If you want cheaper carrier gas then N2 is best option but the limit of detection compromised.

TCD as everybody said. It is not important The origin of he hydrogen.

I agree the best economic choise

The best is TCD

TCD is enough and economical

Use TCD with Ar or N2 as the carrier gas.

Yes, TCD is the best option, with N2 as the carrier gas.

Dear All, Thanks for your answer and sharing your expertise.

TCD is good enough.

TCD is the best choice!

I will agree with everyone. Use a TCD with nitrogen as carrier gas.

Thanks for all for your advice, I will go for TCD

TCD is the best

Yeah, all are giving the right answer. TCD is the best choice for detecting H2 gas with N2 as carrier gas.

Can someone pls cite some reference for these suggestions, i.e., H2 detection by TCD with N2 carrier gas, are best.

Why you think N2 is the best? I prefered Ar because N2 cause some of noise in the TCD signal, of course, N2 is cheap

The "best" carrier gas is going to depend both on the van deemter equation, which expresses linear velocity of carrier gas and theoretical plates (separation efficiency); and your particular application. Plus, price--Helium is very expensive these days.

I've read of things like "nitrogen make up increases response on FID" and "running TCD at a lower temperature increases response" but most of the time these effects are very slight and not always noticeable. It is far more important to have clean gases (both ultra pure sources as well as filters--the best of which have visual indicators of their integrity) and to make sure the system is leak free.

Also, in the case of the TCD the detector should never be exposed to oxygen at high temperature, particularly when the filament is energized.

@Alex Graettinger

Hii Alex

Could you say why running TCD at a lower temperature increases response? And what will happen when it will be exposed to oxygen at higher temperature?

@ alex

Alex thanks, i have also agree with you that pure gases are required to reduce noice..

Hey, check this document: http://www.chem.agilent.com/Library/Support/Documents/a16093.pdf

I've tried running the same sample (in this case hexadecane dissolved in isooctane) at detector temps of 150, 200, 250, and 300 with reference = 20 mL, make up = 2 mL and didn't notice a difference :). The document also notes that very reactive compounds (particularly acids and halogenated compounds) will decrease filament life, I know of someone who was working with phosphoryl and sulfonyl chloride with TCD and they had to replace their detector twice that year.

If you won't be using the TCD for a long period of time you should remove the column, and seal the fitting with a swagelok nut. When you decide to use it again just install your column, run inert gas through it for 20-30 min before heating, and then after heating it to the operating temp allow it to equilibrate for another 30 min or so before turning on the filament. If the whole GC has been idle for weeks or months or whatever I like to put the inlet in split mode with a split flow of say 300 mL/min. This way the gas supply lines and the inlet get purged with many volumes of gas and any air and moisture that has worked its way in goes away without being sent through the column and detector.

Like the document says, reactive compounds can attack the filament and change its resistance--and at 250 C oxygen in air would be reactive enough that you want to avoid it (a leak at high temp once or twice is no big deal, but its best to avoid.) If the column is exposed to air at high temp there are problems as well, the column may become damaged over time and you will see an elevated baseline due to column bleed.

In my experience TCD takes much longer to settle down than an FID, at least 3 hours or so. I like to install my column and then let it sit hot with gas flowing over night, the repeatibility/injection precision is much better (say 4% RSD after only 3 hours, but

@ Hii Alex

Many Thanks for your explanation

If you want to measure hydrogen 0,01?? Which has the best perfomance for such concentrations?

Surely TCD. Ar is the best carrier gas (cheap compared with He). If you use Ar, you will be able to detect N2 and O2 as well. The best column is a capillary molecular sieves at 70 C, but it requires often reactivation at 200 C overnihgt

In order to increase sensibility of the GC you can also use a longer loop, i.e. 1mL, instead of 250 uL which are the loops commonly used.

Dear all thanks for your valuable suggestions...

Coming from experience, use Ar as your carrier gas, and a TCD detector. You don't want nitrogen as your carrier gas for two reasons: (a) if you see the nitrogen peak spontaneously increase, you know you have a leak. If you're doing an oxygen evolution experiment, using nitrogen as a carrier gas will leave you unable to determine whether the oxygen evolved is from a leak or from the photocatalyst. (b) if you're testing a nitride or oxynitride you can check if it's degrading or not through nitrogen evolution.

edit: Also, if you want the best results in a small time, increase your oven temperature to make gases come through the column faster, and tune TCD temperature with flow rate to increase the signal to noise ratio.

The better detector to follow the formation of gaseous hydrogen is of thermal conductivity.

You may decide about suitable detector considering available volume of gas sample and also approximate concentration you expect. I have quite good experience in detection of H2 in the range of 3-5 ppm with PDD (in the case of methanogenic hydrocarbon degradation) and also ~ 10-15 ppm with TCD (syntrophic acetate degradation coupled to sulfate reduction). In both cases volume of samples was quite big. In our setup PDD was quite sensitive and to measure high H2 concentration (~ 10 and more vol %) I had to dilute sample by several times; with TCD I just decreased the volume of injected sample.

Tcd or ms

br

We analyzed our gas samples at 35C, gas carrier was Helium (for detector PDD -Pulsed Discharge Detector Model D-4-I-TQI-R), then conditioning of the column by heating to 200C.

@ Le Phuc: our target is detection of min 50 ppm hydrogen....

Thanks Mahfujur and Alexander for sharing details.

at 50 ppm H2, I think you should use MS.

BR,

Thanks Le...

Dear Rajesh Jagannath Tayade sir,

Can I know the price of TCD dector and gas chromatography in INR.

You can use TCD with Argon as carrier gas for detecting H2 as they have very high conductivity difference. But careful about other compounds generated from your photo-catalytic reactor. You may get H2 within at 2-3 min in GC. But your method should be around 20 min by holding tolerably high temperature (e.g. 200 C)  at least to check other compounds. Otherwise those will affect your later analysis.

Dear Rajesh,

In order to detect hydrogen gas using the TCD, you need to be careful of the carrier gas you are using.H2 can be detected in TCD when the carrier gas is Helium, but the response is very low due to the thermal conductivity of Hydrogen (0.1805 W·m−1·K−1) and Helium (0.1513 W·m−1·K−1) were very near. 

Thermal conductivity of Argon 0.017.72 W·m−1·K−1, very far from Hydrogen thermal conductivity. Thats why generally Argon carrier gas was used in TCD for Hydrogen detection and well response.

Hope this helping