Dear Sir. Concerning your issue about the measuring of Total Phenols and Tannins with the Folin Ciocalteau Reagent. According to the method, you can use Sodium carbonate (20%) and prepare it by the following: Weigh 40 g sodium carbonate (xiO H20), dissolve it in about I 50 ml distilled water and make up to 200 ml with distilled water. I think the following below links and the attached files may help you in your analysis:

http://www.imedpub.com/articles/extraction-of-phenolic-compounds-and-quantification-of-the-total-phenol-of-grape-pomace.pdf

http://www.rroij.com/open-access/estimation-of-total-phenol-tannin-alkaloid-and-flavonoid-in-hibiscus-tiliaceus-linn-wood-extracts-41-47.pdf

http://www.japsonline.com/admin/php/uploads/1413_pdf.pdf

Thanks

The answer is very simple and that is your calculation is wrong (as per your formula Na2CO2 does not exist. It has to be Na2CO3). By diluting it as 1:1 it should since the salt prescribed is decahydrate.

Hi!

I am sorry, it was a typing mistake I was very tired! I meant Na2CO3. What do you mean with dissolving it 1:1? I should prepare it as said (40g in 200mL) and then dissolve it 1:1? Why?

We tried to adjust it by the molecular mass as follows: molecular weight of the decahydrate is 286g and the mw of the anhydrus is 106. So if from the anhydrus I need 40 grams from the decahydrate I need 14g. But this does not work... So I am very interested in finding out the logic behind your answer.

Thanks,

Maria

That is the mistake which you did in your calculation. I anticipated it but I wanted it to be told by you. Look, you compensated the reduced weight with Na2CO3, but forgot that the reduced weight was that of water and not of Na2CO3 and there you made the mistake, which got automatically corrected when you diluted with water. Secondly, the decahydrate salt is crystalline, whereas the anhydrous salt is amorphous which is more lighter than the crystalline compound not by the reduced weight of the 10 molecules of water but even beyond that. All these when summed up got corrected when the solution was diluted 1:1 with water. Nevermind, carry on with your experiments.

Dear all,

We use this method which is very simple:

The total polyphenol contents were evaluated using the Folin–Ciocalteu method [19] with modifications. 500µl of dilute extract was mixed with 2ml Folin–Ciocalteu reagent (diluted 10 times with distilled water). After 5 min, 2.5ml of sodium carbonate solution (7.5%) was added and the mixture was allowed to stand for 90 min with intermittent shaking. The absorbance of the resulting solution was measured at 760 nm. The phenol contents were expressed in terms of milligrams of gallic acid equivalent per gram of dry weight (mg GAEg-1 DW).

for condensed tannins we used:

Total tannins were determined according to Rebaya et al. (2015) [21] with slight modifications. 12.5µl of extract were added to 750µl of vanilline and 375µl of HCl. The mixture was then shaken and incubated at room temperature for 15 min. The absorbance was measured at 500nm and the tannin content was expressed as milligrams of catechin equivalent per gram of dry weight (mg CEg-1DW).

In addition to the contributions, this article can be helpful.

Hi! Regarding the calculations for the anhydrus I still do not understand why they are wrong... When you are adding 40g of decahydrates, only 37% of those 40g are Na2CO3, which is 14.83 g. Since the anhydrous is pure, I should only add 14.83 g. This is how I see it… I still do not understand your answer and why it gets corrected when I dilute it 0.1…

Thanks a lot to everybody!

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