ELIMINATION OF DISSOLVED SULFIDE INTERFERENCE IN THE FLOW-INJECTION DETERMINATION OF SIGMA-CO2 BY ADDITION OF MOLYBDATE

A previously described flow injection method for the analysis of Sigma CO2 included the addition of ZnCl2 to some samples before analysis in order to precipitate dissolved sulfide (which interferes with the met hod) as ZnS. However, the use of Zn2+ in samples with high concentrati ons of dissolved sulfide causes the coprecipitation of ZnCO3, and in o ur experience with this technique, ZnCO3 also precipitates even in the absence of dissolved sulfide. The addition of molybdate effectively c omplexes dissolved sulfide without interfering with the determination of Sigma CO2 by this technique.