Hi everyone,
In this question, I have multiple problems.
To start with, I wanted to titrate the quantity of fatty acid by doing a saponification of sunflower oil by putting an excess of KOH/EtOH, in order to convert all triglycerides into free fatty acids. After this i titrated the rest of KOH which did not react with HCl.
Here is the values :
m (Sunflower oil) = 10,1 g
[HCl] = 0 54 mol/L
[KOH] = 0,49 mol/L (determined by a previous titration)
VKOH = 10,00 ml
Veq blank = 8,6 ml
Veq Sunflower oil = 0,3 ml
Then, I used this formula to determine the percentage :
FFA (%) =[(Vblank - Vsun.oil) × [HCl] × MM sun oil × 0,1] / m(sun.oil)
With my values, I found 12,5% of free fatty acid in 10,1 g of sunflower oil.
These are my problems :
- the saponification value and the FFA doesn't correspond to theoretical values. I made 2 different method and I found the same results.
- for the molecular weight of fatty acid in sunflower oil, I took the average molecular weight of fatty acids : i found approximately 252 g/mol (by doing the sum of fatty acids fraction multiply by their corresponding molecular weight).
If you want more details, don't hesitate.
Thank you,
Best regards.
Best results (FFA profile and quantification) you will get from GC-MS only.
The calculation of % FFA depends on the type of titrated sample and the fatty acid to which the result is to be calculated. The result is calculated as mg(KOH) / g or as %fatty acid (mainly as %oleic acid with Moleic acid = 282,47 g/mol). https://www.ysi.com/File%20Library/Documents/Titration%20Applications/XA00080-FFA-Application-Note.pdf
Check https://fssai.gov.in/upload/uploadfiles/files/Revised-method-acid-value_Oils_Fats_20_02_2018.pdf
Also check https://link.springer.com/article/10.1007/s11746-012-2111-1
@Chinaza Godswill Awuchi
Thank for your answer. I already have the document of your first message.
So if i want to calculate FFA of a sample with a mix fatty acid, I can't.
I must only have oleic acid or does it count like all fatty acid ?
Because i try to calculated the average molecular mass of FFA of Sunflower oil, and i wanted to know if it works ?
For the average molecular weight, I manage to do like this, on the picture below :
Kindly check this one:
Article A Visual Titration Method for the Determination of the Acid ...