It's basically like this, but you also take into consideration the response factor of the different fatty acids by running standard curves of individual FAMEs.
run the IS (internal standard) with the samples. Base on the area of IS peaks you can claculate the concentration of fatty acids
1. Yield of biodiesel(%) =mass of biodiesel obtained / mass of oil used
Normally we get an yield of 95-100%. Mass of biodiesel ( mass of oil + mass of alcohol - mass of glycerol - mass of unreacted chemicals ) it could be greater than the mass of oil. Theoretically it possible to have an yield slightly higher than 100%.
Method : measure weight of row oil before the reaction and weigh biodiesel after reaction and post treatment.
2. Ester Content (%)= cumulative mass of methyl esters/ mass of biodiesel.
It is very important to understand that biodiesel does not means that its 100% methyl ester (or pure) it may even contain un-reacted triglyceride and partially reacted mono-glyceride and di-glycerides. Fatty acid methyl ester /ester content could calculate using EN-14103 method. According to EN-14103 minimum ester content should be 96.5%. we should use an internal standard like C17. In GC area of a peak is proportional to the concentration of that component.
method
a. take a known amount of internal standard (x gram) and mix with known amount of biodiesel (y gram).
b. perform Gc test
c. find out area corresponding to C17 ( area A)
d. find total area (Area B)
Please try to understand that y gram biodiesel does not contain y gram of methyl ester it contain 'U' gram of methyl ester and 'V' gram of contaminants ( we dont know value of U and V , test doing to find these values)
Area A proportional to x gram
total area corresponds to x+U gram not for x+y/ x+U+V
Area B proportional to x+U gram
Area (B-A) proportional to U gram
ester content = U/y
U= (B-A)*x/A
ester content = (B-A)*x/(A*y)
Ester content(%) = ((Area total/Area C17:0)-1)*(mass of C17:0/mass of biodiesel)
3. Conversion Efficiency(%).
It denotes amount of raw oil converted to methyl esters.
Conversion Efficiency(%)=Ester content(%)* Yield (%)
Note:
1. If the ester content is above the limit (96.5%) then other physical properties like density and viscosity will be within the limit.
2. if you loose biodiesel during washing or though any other way , it reduces the yield and there by conversion efficiency but not ester content value.
Dear Suraj ck
I used Ester content method using formula stated
Ester content(%) = ((Area total/Area C17:0)-1)*(mass of C17:0/mass of biodiesel)
After calculating several of my samples, I found out most of the values of ester content on my samples are above 100% (e.g. 110%, 120%). What does that mean?
My samples are biodiesel derived from palm oil (waste cooking oil) undergone transesterification process.
Dear Suraj ck
Weight for sample 1, sample 2 and sample 3 I used for preparation are 15.8mg, 15.4mg and 14.9mg respectively. For preparation of sample, I weighted the amount mentioned (0.02ml) mixed with 0.08 ml of Methyl Heptadecanoate solution (5mg/ml). Sample 1 shows an understandable value, but for sample 2 and 3 shows ester content higher than 100%. Please ignore the component name as it is not calibrated. I only focused on visible peak value such as 13.177, 14.325, 15.363 and 15.528. The peak of Methyl Heptadecanoate solution is at 14.325.. Please guide me..
I request you to take at least 10-20% heptadecanoate by mass to reduce the error.
In your case:
mass of Methyl Heptadecanoate = 5(mg/ml)*0.08(ml)=0.4(mg)
% Methyl Heptadecanoate in total mass (sample 1)= 0.4/(0.4+15.8)=2.46%
in ma opinion this amount is very less, even a small error in gc analys will affect whole readings and as you know normal GC is not a very accurate equipment.
you plz run same sample 5 times and check error of GC analysis, also use extra Methyl Heptadecanoate ( say 10-20%) and repeat the experiment.
How do you calculate Fatty acid methyl esters percentage from a GC-MS data(Chromatogram, library, spectrum)
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