I am estimating free and bound phenolics (after alkaline hydrolysis) using folin ciocalteu method. No problem with bound phenolics estimation as it gives blue color after incubation and the color is similar to that of standard ferulic acid test tubes. But with free phenolics sample I am not able to get the blue color after incubation instead the end color is green. I wonder anyone ever faced this situation. Also I wonder if there is no or very less phenolics present in the sample it would give such different end colors.
please check
http://nutriweb.org.my/publications/mjn0013_2/mjn13n2_art5.pdf
Hi,
I totally agree with Phillip Morris qua the limited usefulness of Folin. In addition, you say you carried out an alkaline treatment. Was that under inert gas (and protected from light? Otherwise your poor phenolics have probably badly deteriorated, They are very susceptible to oxidation in alkaline conditions. Why not just us the spectrum of ferulic acid? We used to do that when I worked with ferulic )acid, it has a distinct UV spectrum which varies with pH but with an isosbestic point. The absorption coefficients for free and bound wer epublished in Carbohydrate Research 154 (1986) 177-187; we gave them in Lebensm.-Wiss. u. - Technol 27 (1994) 59-66
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