# Hydrogen concentration measurement without gas chromatography

Please suggest ways to measure $$\ce{H2}$$ concentration in a sample of gas containing $$\ce{HCl},$$ $$\ce{CH4},$$ $$\ce{N2},$$ $$\ce{CO2}$$ and trace amounts of chlorosilanes without GC.

The problem is that I don't have access to another carrier gas like argon and helium. I need a sensor that can measure $$\ce{H2}$$ in a corrosive gas mix. Expected concentration $$\phi(\ce{H2})\approx 10\,\%.$$

• What instruments do you have access to? Jul 7 '21 at 14:30
• Do you have access to mass spectroscopy? Some of them may be portable (Wikipedia entry). Jul 7 '21 at 14:43
• Ordinary mass spectrometry is really bad for hydrogen until and unless the user has tons of money to spend ;-) Jul 7 '21 at 14:48
• sciencedirect.com/science/article/pii/S1044030502004312 Jul 7 '21 at 14:49
• @ToddMinehardt: we have a GC with a TCD detector using H2 as carrier gas. We can technically move to a different carrier gas, but that is not preferred in this case, as this is a dedicated GC for trace methane measurement in a H2 stream. The gas sample in question has ~ 10% H2 content, hence GC seems to be an overkill. Was wondering if there are other portable cost effective techniques for such bulk H2 quantification. Jul 7 '21 at 15:51

There are commercial, calibrated, hydrogen detectors, such as those from GasSensing or from Mcmaster-Carr, but you'd have to check with the supplier or manufacturer to determine if the other gases give a false reading, or, particularly silanes, poison the sensing element.

You can also make your own device using a sensing element, such as SGAS701 from Renesas, or, for US\$5, the Hydrogen Gas Sensor - MQ-8 from SparkFun.

Be aware of some limitations of these sensors:

• Those catalytically measuring the heat generated from hydrogen combustion require oxygen in the stream.
• Some gases, such as silanes, may poison the sensor or build up a coating on it preventing gases from contacting it.
• Other gases, such as methane, $$\ce{CH4}$$, may give false readings.

You likely will need to contact the vendor's support for specifics; the online information, sch as that for the ATI electrochemical sensor, does not cover the specifics of your situation.

BTW, you might mention the desired accuracy and repeatability for these measurements.

• The problem is not detection, I am looking to quantify hydrogen vol fraction. Jul 8 '21 at 16:13
• @user112894, as mentioned, what is desired accuracy and repeatability for these measurements? The sensors mentioned are quantitative, but without knowing your specific needs, you will not get a useful answer. Jul 8 '21 at 20:10

"The temperature of liquid nitrogen (−195.8 °C) can readily be reduced to its freezing point −210 °C (−346 °F; 63 K) by placing it in a vacuum chamber pumped by a vacuum pump." Wikipedia

A gas sampling tube:

or perhaps even this:

with a pressure meter

attached could be used to take a sample, then the total pressure could be read after cooling to condense all the gases except hydrogen.

I realize this is crude, but it would be fairly cheap, except for the liquid nitrogen and pump.