Hi Apurba

I assume you are referring to the % yield detected by GC-FID from a solvent extraction of some sort? For this you will need to use an internal standard added to your sample at a concentration you know (weight/volume). Then when analyzed by GC, compare the peak areas of your sample peaks to that of your internal standard peak. If you require a total yield then divide the total peak area (not including the solvent peak and internal standard peak) by the peak area of the internal standard. Then multiply this by the concentration of the internal standard in your sample, this will give you a good estimate of the concentration of your total detected peaks. Then from this determine what was originally in the material extracted, correcting for any concentration steps and the volume of the original extraction. Here you should have an amount (g) that you can then divide by the amount of material you extracted which can then be reported as a percentage. This percentage will be a good approximation of the yield as detected by GC on the column you have selected to use.

Thanks. I am doing transfer hydrogenation catalysis. so what is the suitable internal standard in this case.

 Please ,can you send me real example about how to calculate conversion? 

[email protected] 

 http://www.rsc.org/suppdata/cc/b4/b408946d/b408946d.pdf

I have the same issue as Maity (transfer hydrogenation, need percent conversion). If we take aliquots of reaction mixture, can anyone share the proper way to calculate percent conversion of each aliquot using an internal standard?

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.