Dear Icell Sharaf,

most of the groups I know use home-made gas mixing stations, which are based on mass flow controllers. These systems are used to mix a carrier gases with (pre-diluted) analyte gases.

You'll find a simple drawing in my PhD thesis (Figure 18), which available on Researchgate. Or see: https://www.researchgate.net/post/What_is_the_ideal_apparatus_for_testing_chemiresistor_gas_sensors

Best regards,

David Degler

The usual approach is to have some "mixing station" (the mix controlled by mass flow controllers). Depending on the concentrations required one could go for mixing the pure gases, or some "diluted" pre-mix. Both are available from the gas supply industry in a multitude of recipes and concentrations.

If you can find some lab with the necessary equipment, you may be able to book some lab time. Otherwise you would have to build your own system, which requires some invests and - more important - some operation experience until things run smooth.

Dear Ulrich!

For indicating NH3, BiJ3 thin films can be used as single-use sensors. They become transparent.

@ Michael Shustov

Learned something new (about BiI3). But "testing" of these single-use sensors could not go beyond checking for sensitivity - "destroying" the samples within the test.

Our guess about the question was more about gas sensors e.g. based on metal oxides that exhibit quantitative, not only qualitative sensing characteristics.

Dear Ulrich!

The application of the reversible reaction of ammonia formation NH3 + HCl → NH4Cl and its thermal decomposition NH4Cl → NH3 + HCl in a solid matrix. The change in chemical composition is controlled by the change in the electrical resistance of the NH4Cl in the solid phase.