Determination of tannic acid precipitated with bovine serum albumin by visible light scattering by a flow-injection system

Abstract

A flow system, coupled with visible light scattering method, was developed for tannin determination based on the ability of the tannic acid to precipitate bovine serum albumin (BSA). The amount of precipitated tannic acid- BSA is measured directly by scattering intensity of visible light (600 nm), which is properly related to the tannic acid concentration and conformed by a particle sizing method. Scattering signals were non-significant compare with background produced by BSA in both solutions lower than pH4 and higher than pH8. The tannic acid-protein precipitates on pipeline wall and sensing cell could be effectively removed by 22 cm of SDS stream. The system performed a linear detection range 70-100 μg/ml of tannic acid with a detect limit 40 μg/ml in pH5 solution. It also could be used in medium solution with detection ranges were over 420-500 μg/ml and 700-1000 μg/ml in pH6 and pH 7, respectively. The proposed method had good correlations (r2 > 0.97) with the ferrous tartrate method in analysis of both one tannic acid and two tea tannins samples. © 2009 Springer-Verlag.