Re: ORGLIST: folin-denis reagent

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From: Jacob Zabicky (zabicky$##$bgumail.bgu.ac.il)
Date: Sun Jun 03 2001 - 06:41:14 EDT


Hello Peter,

I have the gut feeling that this and the Folin-Ciccateau methods are a
little bit of "Black Magic." You get color all right, you have a linear
range of concentrations and that's fine too, but you cannot exactly say
what causes color formation, and that's not the best analytical situation
to have. It may be suggested that if you have the possibility of running
your own stuff as standard (for example, if you have some dry mixture of
your phenols), you prepare a calibration curve with that, following an
exact analytical procedure, and you stick to it.

All the best,

Jacob

At 13:05 1/6/1, Peter C. Daniel wrote:
>I am using the folin-denis procedure to determine total phenols in
>extracts but have run into a few problems somebody might be able to help
>me with. First, the AOAC methods states that the standard should be .1
>mg/ml. When I used this I got an absorbance close to zero. In the archives
>of this list (posted by Jacob Zabicky 15 May) a number of replies
>indicated an important difference in the standard. Namely that the
>standard should be 10mg/mL. A web page was cited with this recipe
>(http://www.stanford.edu/group/Vitousek/folin.html)When I used this as the
>standard I got a blue-greenish solution which had an absorbance of .2
>units (adding 1 ml of standard solution). That still seems a bit low to
>me. Any suggestions?
>
>Peter Daniel
>Dept of Biology
>Hofstra University

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