So I extracted 1g of sample in 10ml of 80% methanol twice (so total volume of solvent used is 20ml) using a sonicator and from the extract obtained I used 100µL of the extract for F-C protocol.
equation of GA callibration curve : y = 0.0057x + 0.0065 ; concentration of gallic acid ranged from 20-100 µL
absorbance obtained : 0.318, inserting this to the equation, I'll get 54.64 µg/ml.
So how do I calculate Total Phenolic Content and express it in mg GAE/kg?
It is not clear what concentrations you used. 20-100 ul is not concentration. Answer me, and we can calculate further.
O.K. If you constructed calibration equation correct, you have 54.64 ug in 100 ul. You have to multiply 200 (20 ml), it is for 1 g and finally multiply 1000, for 1 kg. Result will be in ug GAE/kg. As you want to have in mg per kg, you will divide 100. Finally your number from calibration multiply just 200 - you will receive result in mg GAE/kg.
Pavel Dostálek Thanks, I understand this calculation. I understand that to calculate TPC , the formula is c*v/m in which c = concentration of gallic acid obtained from calibration curve in mg/mL, V = volume of extract in ml, m = mass of extract in gram.
I just don't understand which volume of extract that we need to use to calculate TPC, is it the total volume used to extract the sample - which in this case is 20ml? or the total volume used in F-C protocol (including volume of F-C reagent+others)? or just the total volume used in F-C protocol - 100ul?
And for mass of extract - is it the mass of extract after it has been dried? or initial mass of sample used for extraction - which in this case is 1g?
Sophia, it is simple: calibration and measurement is done under the same protocol, you just use part of extract - in your case 100 ul from 20 ml (total volume). 1 g was used for 20 ml.
Sometime better use own calculation than use equation which is not understandable.
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