SPECTROPHOTOMETRIC DETERMINATION OF TANNIN IN TANNING EFFLUENT WITH AFLOW-INJECTION SYSTEM

The use of the Folin-Ciocalteu reagent in the spectrophotometric deter mination of polyphenolic substances (total tannins) in tanning effluen t by means of a chemical analysis system based on flow injection (FI) is described. Chemical variables and variables related to the FI syste m were evaluated. The proposed method permits the execution of up to 2 50 determinations per hour, with good precision (relative standard dev iation <3%, n = 10) and a broad linear range (5.0-100.0 mg l(-1) tanni n). The results are comparable to those obtained by the conventional m ethod 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).