Online determination of trace amounts of tannic Acid in colored tannery wastewaters by automatic reference flow injection analysis.

A simple, rapid and sensitive method was proposed for online determination of tannic acid in colored tannery wastewater by automatic reference flow injection analysis. Based on the tannic acid reduction phosphotungstic acid to form blue compound in pH 12.38 alkaline solutions, the shade of blue compound is in a linear relation to the content of tannic acid at the point of the maximum absorption peak of 760 nm. The optimal experimental conditions had been obtained. The linear range of the proposed method was between 200 mug L(-1) to 80 mg L(-1) and the detection limit was 0.58 mug L(-1). The relative standard deviation was 3.08% and 2.43% for 500 mug L(-1) and 40 mg L(-1) of tannic acid standard solution, respectively, (n = 10). The method had been successfully applied to determination of tannic acid in colored tannery wastewaters and the analytical results were satisfactory.