The determination of sulfide in the aqueous environment

Direct measurements were made by use of a sulfide ion-selective electrode in conjunction with a double-junction reference electrode and an Orion Model 407 A/F specific ion meter. This method enables simple and rapid determinations of the total sulfide ion concentration in water. Total sulfide was determined in samples collected from lakes in Fort Bend County. Texas, which ranged from 4 ppb to 18 ppb and from the Houston Ship Channel which ranged from 13 ppb to 42 ppb.A series of experiments shows that (1) the rate of oxidation of S^2? exposed to air is about three times slower for solutions containing the sulfide antioxidant buffer (SAOB II) and (2) the rate of oxidation of S² in tightly capped containers is about twice as fast for solutions not containing SAOB II than for solutions containing SAOB II.It was concluded that the use of SAOB II almost eliminates the problem of air oxidation of sulfide ions during direct measurements and that sulfide ion concentrations (as low as 4 ppb) can be determined directly in the laboratory and in the field by use ofthis electrode method.