In definition TPC by Folin-Ciocalteu, when we add Sodium carbonate (20%), fall residual material (white colour).Sample we explore is grape cake water extract.
Condition: 7.9 ml water + 0.5ml F-C reagent + 0.1 ml sample(water extract grape) - wait 8 min, then take 1.5 ml sodium carbonate = fall residual material (white colour).
What is this? Do this residual material influence at result?
Dear Sir. Concerning your issue about the residual material in Folin-Ciocalteu reaction. The Folin-Ciocalteu method is described in several pharmacopoeias. The reaction forms a blue chromophore constituted by phosphotungsticphosphomolybdenum complex, where the maximum absorption of the chromophores depends on the alkaline solution and the concentration of phenolic compounds. However, this reagent rapidly decomposes in alkaline solutions, which makes it necessary to use an enormous excess of the reagent to obtain a complete reaction. This excess can result in precipitates and high turbidity, making
spectrophotometric analysis impossible. To solve this problem, Folin and Ciocalteu included lithium salts in the reagent, which prevented the turbidity. The reaction generally provides accurate and specific data for several groups of phenolic compounds, because many compounds change color differently due to differences in unit mass and reaction kinetics.I think the following below attached may help you in your analysis:
Thanks
Thank you for the answers.
When we prepare sample, after extraction we also perform spinnig for 20min/5g. Then, we take supernate, and use it in experiment.
Some photo of exp.
First photo. On this picture, there is 4 tubes. (before incubation)
In tube IV - 7.9 ml water + 0,1 sample + 0,4 ml F-C reagent + 1,5 ml Na2CO3 20%
In tube III - 7.9 ml water + 0,1 sample + 0,3 ml F-C reagent + 1,5 ml Na2CO3 20%
tube II - 7.9 ml water + 0,1 sample + 0,2 ml F-C reagent + 1,5 ml Na2CO3 20%
tube I - 7.9 ml water + 0,1 sample + 0,1 ml F-C reagent + 1,5 ml Na2CO3 20%
pH of Na2CO3 - 11,435
Second photo. After incubation at 40C/20min.
H Maksym Labazov, I am experiencing the same problem too. Have you got the solution for this problem? Because the absorbance reading is not stable.
Thank you in advance.
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