A single FIA system coupled with reduction and distillation processes for the determination of sulfate ion by spectrophotometry.

In the present work, all steps of the sulfate reduction procedures, such as reduction, distillation and sulfate determination were joined in only one FIA system. The formed sulfide was on-line determined by employ the Fisher reaction. The proposed method presented a LOD of 1.00 μg L(-1) and a LOQ of 3.33 μg L(-1), well lower than the most commonly used turbidimetric determination, with no significant interferences. Additionally, we reached an analytical frequency of 6 measurements per hour, including all steps, beginning with the introduction of the sample up to the signal reading. Therefore, it revealed very fast, low reagent/sample consumption, agreeing with green-chemistry statements. This method has also a wide linear range (3.33 up to 1000 μg L(-1)), being useful for both low and high sulfate concentrations.