who knows a good analyzer for both CO2/CO analysis

[LDCCL]

we want to find a good dedicated analyzer for CO2and CO in all kind of inert gas analysis, the concentration is from ppm level to percentage, hope LDL is ppb level, because we will test standard gas within 10ppm, i know NDIR is a good choice, but some analyzer isnt avaliable to meet the requirement, who can provide information to me, i am do appreciated, my email : ccl760@sohu.com

Many thanks in advance

Regards

[chromatographer1]

You can ask Siemens or PE about their analyzers (Agilent and VICI with others also have them)

Rodney George
consultant

[LDCCL]

I have contact sales representative of these company, and they havent instruments such like this to meet the extreme low level CO2/CO analysis.

Thanks and Regards

[AICMM]

LDCCL,

If just CO/CO2 in inerts, I would recommend (and this pains me greatly) that you look at FTIR instrument. With a couple of different cells for different path lengths, you should be able to cover the analytical range you are interested in on the same instrument bench.

If you want to stick to GC, I would suggest looking at a carbon molecular sieve column (ShinCarb or Carboxen) and an HID detector. In this scenario you would have to change loop sizes on your injector to go from ppm to low percent but that is not too difficult to do. Considering you already have GC, this would probably be the cheaper route to go.

Best regards.

[LDCCL]

Hi AICMM

Thanks for your information, in fact we have lots of GC in here, but for the CO2/CO results, we can get repeatablity but no linearity with Hayesep Q columns, i am puszzed and try to find another method for low PPM CO2/CO/ in inerts analysis, as far as I know, NDIR LDL almost at 0.5/1 ppm, so probably couldnt to meet our requirement, We have DID detector, can you give me details about the columns you provided, so we can contact the supplier to talk about the issues. and also i am told there is a new method for CO2/CO analysis, that is to transfer them to CH4 with Ni catayst at high temperature then test it with FID, do you have any comments

Thanks again!
I am anxious to hearing from you

[chromatographer1]

I am surprised that Siemens would not quote ppb CO and CO2 GC analyzer, at least in the 250-500 ppb range.

I believe that most industrial apps for less than 0.1 ppm use spectroscopy not chromatography as AICMM suggests.

I would also suggest that any column that uses a carbon backbone support or phase would not be useful in measuring CO or CO2 unless special precautions of hardware, sampling, and carrier gas are taken.

Rodney George
consultant

[Ron]

I would think that a GC with a methanizer and an FID would easily perform this analysis. The FID has a much lower detection limit that the TCD, and the linear dynamic range is much wider than an HID.

[AICMM]

LDCCL,

Ron is right, a methanizer (the nickel catalyst you talk about) could be an effective solution for you. The only problem it may have (still) is getting low enough but you may be able to put in a big enough loop. I am sure your GC vendor (Gow Mac, right?) will have a set up for their GC's since it is a pretty common solution. The one thing you have to watch for is hydrocarbon contamination but if you are only running inert gases it should not be an issue. Nice thing is the inert gases will not show up.

Do you get good separations on the Q?

Best regards.

[chromatographer1]

The problem with a methanizer is the chromatography co-elution of CO with some inert gases, like Ar. N2. Since the conversion of CO requires hydrogen gas getting a complete reaction of the CO in the highly diluted plug (the co-eluting Ar, or N2) a complete reaction is problematic. You could lose accuracy at low levels, which is the context of our discussion here. Difficult analyses don't come cheaply and an analyst does what an analyst has to do to get ACCURATE results. A big sample plug using a big sample loop would be fine if the sample matrix was hydrogen, but for anything else?, well, there isn't a straight forward answer, certainly not an inexpensive one. And remember that a big sample loop means a broad CO band (plug) which gives a wide not a tall peak. To have low levels be reached the CO has to be refocused where its peak width is narrower than the width of the sample plug entering the column. How can that be achieved? And remember that there is no magic conversion of CO instantaneously achieved with a catalyst. This effect also broadens out the peak. As much as I love chromatography, I do believe that you may be trying to exceed its capabilities for this analysis, but good luck with spectroscopy.

Rodney George
consultant

[dpr]

We use a ppq column for sereration followed by a methaniser onto a FID.

[LDCCL]

Hi All

Thanks for you all are interesting my question, in fact, we are more focus on testing with low concentration CO2/CO( CO2 is main component we want to test) analysis, i think high concentration CO2 testing like hunderds ppm or pecentage we can use a TCD, should be not an issue, but for low level like PPm, we always cant get good results than theroetical value provided with chromatograph, for example, 4ppm CO2 in N2, the results we tested is 6ppm, and repeatability is very good and graph is also beautiful,the columns we used is Hayesep Q,most of our GC have two columns that is one pre-column and seperation column, the precolumn was used to backflush the balance gas with the help of 10-port valve to prevent them into the detector DID, so i want to try another method for CO2 analysis, I am very appreciated any ideas and information you provided.

Many thanks and Regards

[kbethune]

We worked with a company to modify our Varian 3800s for CO/CO2 analysis in H2 using haysep db, Mol. sieve 5a, methanizer and FID.

Our work is on the order of 0.2 ppm - 200 ppm CO/CO2. We get detection limits around 0.05-0.1 ppm....

We use a Haysep dB (or N) in combination with a mol. sieve that goes into bypass mode for water and CO2. ....the CO/methane and others fill the mol. sieve, then that goes into bypass when the CO2 elutes out of the haysep, and then flows through the methanizer and onto the FID. After the CO2 comes out, the mol. sieve is placed back in series, and the methane and CO go through the methanizer. The CO peaks are a little spread out. This makes for about a 12 minute method (not considering sample loop filling), which we run for 6 minute flow through because our sample flow rates are so low.

Had to remove all the electropolished nickel tubing in the system to get down to the sub ppm level, but we have gotten great results with this approach. We also pulse the methanizer with some air before every run while the sample loops are filling to oxidize any carbon buildup in the methanizer. That helped with long term stability.

Credit goes to lotus consulting for the design of the system.

[jlkishore]

we have a varian 450GC for CO2 analysis which works on the same priciple as kbethune has explained. My problem is I don't see a good peak for CO2 in TCD but a big peak in FID which is from the methane formed from CO2. Is it possible to get a good peak in TCD also. Another peoblem is we use Ar as carrier gas which might supress CO2 as both have mol. weight in the same range. I tried to use He as carrier gas but our CO2 sample itself is diluted in Ar. Is it possible to get good CO2 peak in TCD for 10% CO2 in Ar sample.
Thanks in advance

[chromatographer1]

Review the thermal conductivity values for Argon and CO2. If their values are too similar you will not be able to get good response for CO2 using a TCD as a TCD measures the difference in conductivity between two gases.

"Is it possible to get good CO2 peak in TCD for 10% CO2 in Ar sample. "

YES. Use H2 or He carrier with your TCD, a 2 to 3 meter 2.1mm ID packed column and a 0.05mL to 0.5mL sample loop with your TCD. Lower carrier flow rates will increase your response. Try to keep oven temperatures below 100°C for maximum separation of CO2 from Ar.

Not having references readily available to me at the moment, you will have to do your own research and look up the values yourself.

With H2 or He carrier you will have no issues using a TCD for a percentage level of CO2 in almost any gas. If you choose to use an Argon ionization detector you will have more sensitivity than you can imagine or ever use but scrubbers and high purity carrier gas is required.

A simple porous polymer column of Q or P type polymer will work very successfully for CO2. (Chromosorb 101, 102, Porapak Q or P, Hayesep Q or P) NO2 will be the only closely eluting possible interference. Look up retention data from Hayes Separations or Waters Corp references.

best wishes,

Rodney George
consultant