ANALYSIS OF GALLOTANNIN IN SUMAC PART I: TITRIMETRIC METHOD FOR THE DETERMINATION OF GALLOTANIN IN SUMAC EXTRACT

摘要

We have developed a method for the determination of gallotannin in sumac extract. Sample preparation consists of acidic hydrolysis of tannin to gallic acid at pH＜2 and high temperature. The hydrochloric acid used to maintain an acidic medium and the gallic acid are titrated with a standard solution of NaOH, 0.1mol/l, in two samples containing equal amounts of HCl and tannin. The absence of systematic errors in the proposed procedure is proven. The reproducibility of the results for tannin content 54.5% is good, S_r = 0.9%, and satisfies technological requirements. This method can be applied for the analysis of gallotannin in extracts from Rhus semialata (Chinese galls) and Caesalpinia spinosa (Tara).