Chromatography Forum

Good Day,
I need help ?!! We are doing the analysis of biodiesel with GC/FID.
How it can be true that total Ester content is 93% m/m (EN14103) and Triglycerides are about 0.61% m/m , Diglycerides are 0,50% m/m , Monoglycerides are 0,62% m/m and free glycerol is 0.004% m/m (EN14105) ??

Why it's not calculate like this : Total ester content is = 100% -(0.61%+0.50%+0.62%+0.004%) = 98,26% ??? Can anyone please help me !???

Silly question are you using the correct solvent to dissolve your sample in. Or this there any methanol from the esterifacation process?

If your feedstock oil is UCO it has polymerized TAGs in it. When TE'd the polymerized FAMEs have higher BPs than the inlet temp and stay behind in the liner or don't go through the column and you lose their peak area.

AZBiodiesel,
Yes we use UCO for biodiesel production.
Can you please explain more !!

Danw9,
there is no more methanol in this biodiesel and no impurities !!

Hello, I have the same question. Have you got the answer?

I use UCO for producing biodiesel. I have the analysis results from a certificate laboratory. They use the standardized method EN-14103 to analyze ester content. In fact, they analyzed almost all the parameters mentioned in EN-14214. However, the total content of the samples were between 91-93% (fatty acids, fats, esters, vegetable oils, glycerides, methanol, glycerol, contaminants, and so on). Only 82-85% were ester.

How is this possible? What can be the other 7-9% of the content?

AngelaEslava wrote:
Hello, I have the same question. Have you got the answer?

I use UCO for producing biodiesel. I have the analysis results from a certificate laboratory. They use the standardized method EN-14103 to analyze ester content. In fact, they analyzed almost all the parameters mentioned in EN-14214. However, the total content of the samples were between 91-93% (fatty acids, fats, esters, vegetable oils, glycerides, methanol, glycerol, contaminants, and so on). Only 82-85% were ester.

How is this possible? What can be the other 7-9% of the content?

It looks like you need to investigate your product deeper than simple EN-14103 and EN-14214. There are two main reasons (explanations) why you have such results and both of reasons are based on your UCO feedstock specs. First reason is the fatty acids profile of your UCO oil - if it is not a common mixture of C14-C24 fatty acids this could be an explanation (it is fixable with a proper analysis-certificate), second reason is the oily material which is not fatty acids based oils - e.g. hydrocarbons, waxes etc. this problem is also fixable but will require some deeper investigation. These two main situations are most common (they are both UCO feedstock based problems), but there are several other possibilities including wrong lab results.

HibaZ wrote:
Good Day,
I need help ?!! We are doing the analysis of biodiesel with GC/FID.
How it can be true that total Ester content is 93% m/m (EN14103) and Triglycerides are about 0.61% m/m , Diglycerides are 0,50% m/m , Monoglycerides are 0,62% m/m and free glycerol is 0.004% m/m (EN14105) ??

Why it's not calculate like this : Total ester content is = 100% -(0.61%+0.50%+0.62%+0.004%) = 98,26% ??? Can anyone please help me !???

There are a lot of other components is biodiesel e.g. waxes, hydrocarbons and something else which can not go through GC column.

Some times you might need to add HPLC tests for this composition, because some of the components of the mixture are not volatile. We worked with couple biodiesel companies in developing universal HPLC procedures and platform for biodiesel analysis.
You can see a brief description of the work described here (two reports on analysis of biodiesel):
https://helixchrom.com/services/method-development/

I am adding another report there this week on analysis of polar components in biodiesel production. All these are not volatile and have no UV activity, so we used ELSD to monitor elution from one of the mixed-mode columns.

We have an expert in the company who knows almost everything about biodiesel, and I am being modest here with "Almost".

Vlad Orlovsky wrote:
Some times you might need to add HPLC tests for this composition, because some of the components of the mixture are not volatile..

Yes, HPLC is one of the methods to approach. For this particular problem (when UCO is used as feedstock) we have a very complex mixture ("UCO") with a broad range of molecular sizes, polarities, and charges. So, we will need to cover a mixture from hydrocarbons (very low polarity) to surfactants and even salts.
I remember, there is an approved method for such task and they recommend to use a SEC column to separate (partially) the components by their molecular weights.

Lipid, thanks a lot! I think you´re right and I need to analyze deeper my product. UCO is a very complex matrix and it may have some compounds that are not so easy to detecte with the classic standards.

(sorry for the late reply, I never received the notification of your answer)