Chemical interferences specifications
The SulfiLoggerTM H2S sensor’s total sensor signal (the sensor reading) is the H2S signal + interferences.
| Gas | Formula | Interference for gases in gas phase (%)1 | Interference for gases in liquid phase (%)2 |
|---|---|---|---|
| Methane | CH4 | 0 | 0 |
| Carbon dioxide | CO2 | 0 | 0 |
| Nitrogen | N2 | 0 | 0 |
| Oxygen | O2 | 0 | 0 |
| Air | O2, N2, Ar | 0 | 0 |
| Nitrous oxide | N2O | 0 | 0 |
| Ammonia | NH3 | 0 | 0 |
| Hydrogen | H2 | 0.8 | 96 |
| Carbon monoxide | CO | 0.6 | 77 |
| Dimethyl sulfide | (CH3)2S | 18 | 18 |
| Methyl mercaptan | CH3SH | 174 | 44 |
| Ethyl mercaptan | C2H6S | 13 | 14 |
| Sulfur dioxide | SO2 | 40 | 1 |
1 Given as signal for the interfering species in % of H2S signal at equal partial pressures
2 Given as signal for the interfering species in % of H2S signal at equal molar concentrations
Examples
The following examples clarify how to interpret the chemical interferences specifications table above.
Example #1
In a gas mixture with 1000 ppm hydrogen sulfide (H2S) and 100 ppm hydrogen (H2), the total sensor signal includes hydrogen induced interference corresponding to 0.8% of the 100 ppm H2. In other words, there is a minor interference signal of 0.8 ppm.
Total sensor signal = H2S signal + H2 interference signal = 1000 ppm + (0.008 x 100) = 1000.8 ppm.
Example #2
In a gas mixture with 1000 ppm hydrogen sulfide (H2S) and 100 ppm methyl mercaptan (CH3SH), the interference is 174 ppm. Since mercaptans give rise to odor nuisances similar to H2S and because the concentrations of mercaptans typically are much lower than the H2S concentration it is seldom seen as a problem to have interference from these molecules.
Total sensor signal = H2S signal + CH3SH interference signal = 1000 ppm + (1.74 x 100) = 1174 ppm.