Spectrophotometric determination of tannin in tanning effluent with a flow injection system

Abstract

The use of the Folin–Ciocalteu reagent in the spectrophotometric determination of polyphenolic substances (total tannins) in tanning effluent by means of a chemical analysis system based on flow injection (FI) is described. Chemical variables and variables related to the FI system were evaluated. The proposed method permits the execution of up to 250 determinations per hour, with good precision (relative standard deviation <3%, n= 10) and a broad linear range (5.0–100.0 mg l^–1 tannin). The results are comparable to those obtained by the conventional method for the determination of tannic acid (114.3 ± 6.4 and 111.7 ± 3.2 mg l^–1 tannin for the proposed FI system and the conventional method, respectively).