Technique for simultaneous determination of [s]sulfide and [C]carbon dioxide in anaerobic aqueous samples

A technique for the simultaneous determination of [S]sulfide and [C]carbon dioxide produced in anaerobic aqueous samples dual-labeled with [S]sulfate and a C-organic substrate is described. The method involves the passive distillation of sulfide and carbon dioxide from an acidified water sample and their subsequent separation by selective chemical absorption. The recovery of sulfide was 93% for amounts ranging from 0.35 to 50 mumol; recovery of carbon dioxide was 99% in amounts up to 20 mumol. Within these delineated ranges of total sulfide and carbon dioxide, 1 nmol of [S]sulfide and 7.5 nmol of [C]carbon dioxide were separated and quantified. Correction factors were formulated for low levels of radioisotopic cross-contamination by sulfide, carbon dioxide, and volatile organic acids. The overall standard error of the method was +/-4% for sulfide and +/-6% for carbon dioxide.