Coulometric determination of total sulfur and reduced inorganic sulfur fractions in environmental samples.

Evaluation of the solid-phase partitioning of sulfur is frequently an important analytical component of risk assessments at hazardous waste sites because minerals containing reduced-sulfur can significantly affect the transport and fate of organic and inorganic contaminants in natural environments. We applied selected methods for the determination of total sulfur, acid-volatile sulfide (AVS), chromium-reducible sulfur (CRS), and extractable-sulfate in standard reference materials and sediment samples from a contaminated site. A coulometric titration method is presented and evaluated for total sulfur, AVS, and CRS. This method is especially advantageous for AVS and CRS determinations because hydrogen sulfide gas evolved during chemical extraction is detected and quantitated in-line; consequently, measurement endpoints can be precisely determined without need for setting arbitrary time limits. The coulometric method allows for improved data quality and increased laboratory throughput of samples. Data on sulfur partitioning are presented for four standard reference materials (NIST 1646a, NIST 2780, CCRMP LKSD-1, CCRMP RTS-3) for the purpose of supporting quality control in environmental studies involving the geochemical and biochemical cycling of sulfur.