Hydrogen microsensors with hydrogen sulfide traps

Hydrogen is often formed in sulfidic environments where interference from hydrogen sulfide has prevented its analysis by amperometric hydrogen microsensors. Hydrogen microsensors were made insensitive to hydrogen sulfide by placing a sulfide trap (guard) containing solutions of heavy metal ions, sulfide-oxidizing ferricyanide, or alkaline chemicals at the sensor tip. The overall most efficient sulfide guard consisted of a solution of ZnCl2 in propylene carbonate which resulted in absence of interference from 5 mmol L−1 hydrogen sulfide and also alleviated any interference from oxygen. The hydrogen sensors with ZnCl2-propylene carbonate traps could be used at temperatures up to 60 °C without exhibiting excessive baseline currents. The ability of a guarded sensor to resolve the hydrogen distribution in a sulfidic microbial mat with up to 2.4 μmol L−1 H2 was demonstrated.