Restoration Procedure For Membrane Covered DO Probes Exposed To H2S Or SO2

When YSI membrane covered dissolved oxygen probes are exposed to hydrogen sulfide (H2S) or sulphur dioxide (SO2) for extended periods they will cease operating in a normal manner. Output current will decrease and calibration may become unstable. Visual symptoms include blackening of the silver anode and/or a purplish-brown discoloration of the gold cathode. Probes exposed to high concentrations of hydrogen sulfide or sulphur dioxide should be flushed and refilled with fresh KCl solution after every use, then a new membrane applied.

The cathode discoloration caused by the H2S or SO2 contamination usually cannot be removed with the lint-free cloth or hard paper as suggested in the probe instructions, but must be removed by abrasive refinishing of the cathode surface. Complete instructions for this refinishing procedure are included in the YSI 5680 Probe Reconditioning Kit which is available from YSI Customer Service.