Vanillin-condensed tannin study using flow injection spectrophotometry

Studies involving the kinetic reaction between vanillin and condensed tanni ns were developed using a flow injection system with spectrophotometric det ermination. A solution of the monomeric compound (-)-epicatechin was used a s the analytical standard. This compound was chosen due to its structure, w hich is similar to a polymeric unit of the condensed tannin present in plan ts. The results indicated that the vanillin-condensed tannin reaction is ti me dependent and affected by the degree of polymerization of the condensed tannin. The flow system allowed (-)-epicatechin to be used without overesti mating the content of the tannin present in the forage legume, guandu (Caja nus cajan (L.) Millsp.), studied. A relative standard deviation (R.S.D.) of <1% was found for a 4 h period work and allowed the determination of about 60 samples h(-1) with a detection limit of 1.05 mg l(-1) for condensed tan nin. When compared to the manual vanillin procedure, the proposed approach can be used with various advantages. (C) 2000 Elsevier Science B.V. All rig hts reserved.