No idea Dear

Folin-Ciocalteu is a method very sensible to the procedure, as describe in the paper Determination of total phenolics, AL Waterhouse - Current protocols in food analytical chemistry, 2002.

If possible, it is always useful to use an international validated method:

ISO 14502-1 (Folin-Ciocalteu)

X Content of anhydrous gallic acid, μg/ml

Y Optical density, 765 nm

Calibration line slope = 0,0132

Intercept value = 0,0113

http://scholar.google.com/citations?view_op=view_citation&hl=it&user=yY-df4UAAAAJ&citation_for_view=yY-df4UAAAAJ:Se3iqnhoufwC

Hello

you need to know only three things,

1. concentration of sample solution

2. regration equation

3. absorbance of sample solution

(no need to calculate how much volume of folin reagent, Na2CO3 are used because in both the sample solution and standards we use same protocol)

You prepared final sample solution having concentration of 500ug/mL and got the sample solution absorbance reading (y) =0.883.

By using the equation y=0.0107*X, 

So, concentration of total phenolic in your sample (X) will be : y/0.0107 i.e. 0.883/0/0107=82 ppm (ug/mL)

In other words, 82 ug/500ug of sample extract.

or, 164 ug/mg >> 164 mg/g >> 16400 mg GAE /100g  freeze dried extract.

Hi,

Ali and Shiva. Thanks for your calculation

 I am having doubt in Ali calculation. How cf= 150 µg/3 ml and 6300 mg GAE/100g freeze extract. is obtained. When calculated, 500 µg/ml x 3= 1500 µg/ 3ml is found.

In the calculation from 1&2, 0.0095 µg GAE/ 150 µg

= 0.0095 µg GAE/ 0.15 mg (0.00015 g=0.15mg)

= 0.0095 µg GAE/0.00015 g

= (0.0095 µg GAE x 100)/0.00015 per 100 g

= 6333 µg GAE/100 g

= 6.3 mg GAE/100g

Can you elaborate the details? Please.

I have calculated in different ways. 

y = 0.0107x => x= 0.883/0.0107= 82.523 µg/ ml

                                                    = 82.523 µg x 20 ml per 20 ml

                                                    = 82.523 µg x 20 ml per 0.01g sample

                                                    = 82.523 µg x 20 x 100 /0.01 per 100g sample

                                                    = 16504600 µg per 100g

                                                    = 16504 mg GAE per 100g sample

Or x= 82.523 µg/ml= 82.523 µg/0.5mg= 82.523 µg/ 0.0005g= 16504600 µg/100g=16504 mg GAE/ 100g

Another method, TPC (mg GAE /g) = C × V/ M, where c = concentration determined from standard curve (mg/ml), V = volume used during the assay (mL), and M = mass of the extract used during the assay (g)

= 0.082523 × 3/ 0.01 = 24.76 mg GAE /g = 2476 mg GAE/ 100g

But, I got the same results with Shiva as per my calculation in one method of calculation. The TPC  = 16500 mg GAE/ 100g is very high compared to the research paper. I have found in some literature that TPC is not an actual phenolic content as F-C reacts with some reducing compounds. Or should I calculate the amount from extraction process? I have confusion in calculation. I got different results.

Jag, I think the equation in Gallic acid is wrong. something is missing. I agreed with Roberto. 

Thanks a lot, Roberto and Ruiz

Ruiz, you have told me" something is missing". What it means? I have not added the intercept value and R2= 0.9974. Please discuss about this.  I have tried many other formula. The results is still different or should i consider from the amount of dried sample used for alcohol extraction before getting the freeze dried extract. Thanking you again.

Hi All,

The calibration and calculation are the easiest part of the analytical method. Firstly, you should follow exactly the analytical procedure because, as mentioned previous, the FC method is easily biased.

If possible, you should follow the ISO procedure.

http://www.iso.org/iso/catalogue_detail.htm?csnumber=31356

Hello Pal

Most of the researchers used Folin-Ciocalteu method for total phenolic content assessment. you can calculate with the help of Gallic acid standard graph by comparing the OD value of sample extract and standard graph. after that you will change this value in mg/ g of gallic acid.

Sir, Robert . I don' get that protocol. It's not subscribed.

 Hi, Reetika

 I used the gallic acid but my value is getting very higher. i.e. =15604 mg GAE/ 100g = 156 mg GAE/g

Hi Jag, you should try the protocol, repeating at least 3 time the entire protocol.

Thank you sir. I will follow that protocol

When getting y = 0.0107 x, what is the unit of x-axis? It is g/L or µg /mL or mg/mL?

Dear Raja, x= µg /mL

Jag Pal for Green Tea leaves the phenolic content is around 20000mg GAE/ 100g tea leaf or more understandably 200mgGAE/ gm tea leaf which OK......so I think your result is just OK...just express in mgGAE/ gm instead of mgGAE/ 100gm

Hey guys, I wanna ask about my TPC (Total Phenolic Contain) calculation.

Here's what I've done

I've maserated 200g of fresh pomelo with 200 mL ethanol, then I've got my crude extract from rotary evaporation process.

I took 50 mg crude extract and diluted it with 5 mL of ethanol.

The next thing, I took 1 mL to test the TPC content.

Then I recieved my standard equation

Y= 0.001x + 0.061, with 0.082 absorbance. So I got x= 21 mg GAE/L.

Here's the question, have I done it right with this calculation 21 * 0.005L/ 0.05 g = 2.1 mg GAE/g extract?

And is it possible for me to convert it to mg GAE/ g fresh weight and mg GAE/ g dry weight (cause I've read a lot of literatures using those unit)

Thank you

according to ISO 14502-1 procedure for calculation of TPC in mg GAE/gm we only use dried weight including the moisture content. Hence, results are always in terms of dried biomass content. Please find the PDF copy of the procedure attached.