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Simple 13 C‐NMR methods for quantitative determinations of polyflavonoid tannin characteristics
Author(s) -
Thompson D.,
Pizzi A.
Publication year - 1995
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1995.070550111
Subject(s) - tannin , pyrogallol , phloroglucinol , resorcinol , catechol , chemistry , condensed tannin , thermosetting polymer , degree of polymerization , carbon 13 nmr , polyphenol , organic chemistry , polymerization , proanthocyanidin , polymer , antioxidant , food science
A simple 13 C‐NMR method for the quantitative determination of polyflavonoid tannin characteristics was developed. The system is effective for use on concentrated (25–50%) solutions of natural and modified tannins. It allows the determination of the average degree of polymerization ( DP n ) of the polyflavonoid, resorcinol vs. phloroglucinol proportion of the A‐ring and catechol vs. pyrogallol proportion of the B‐ring. The results obtained are consistent with existing data determined by other techniques. The method was also tried with tannin extract that was modified to form thermosetting adhesive intermediates, and with tannin modified by sulfonation, a common commercial modification for these materials. The results were again consistent with what was expected. The method affords the possibility to follow by a simple technique the variations in DP n and M M̄ n (number‐average molecular weight) induced by chemical modifications of polyflavonoid tannin extracts and thus to correlate them with relevant structural modifications affecting these parameters. The method is not capable of distinguishing the relative proportions of the four important flavonoid units present in commercial polymeric tannin extract. It can only distinguish the relative proportions of (i) (procyanidins + prodelphinidins) vs. (profisetinidins + prorobinetinidins) and (ii) (prorobinetinidins + prodelphinidins) vs. (profisetinidins + procyanidins). © 1995 John Wiley & Sons, Inc.