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.