I think you are asking the wrong person - I am a psychiatric epidemiologist, and I think Research Gate has me linked to someone else.
Best wishes,
Brian O'Toole.
Can costisone peritendon injection (1cc of Celestone or else).... Available from: https://www.researchgate.net/post/Can_costisone_peritendon_injection_1cc_of_Celestone_or_else_diffuse_into_a_surrounding_joint?discoverMore=1#59a79c4093553bfc5542cc9f [accessed Aug 31, 2017].
You may find the answer from the publication suggested below. They used the colorimetric method to quantify tannin. These methods have been commonly suggested in publication articles.