Introduction

For biodiesel to be used as a motor fuel or blended with petroleum diesel, it must conform to standard specifications (ASTM D 6751 or EN-14214). There are standard GC methods in use today to determine if biodiesel conforms to the standard specifications, one of which is EN-14103, used to determine the ester and linoleic acid methyl ester content. Other methods include EN-14105 / ASTM D 6584 (free and total glycerin and mono, di and triglyceride content) and EN-14110 (residual methanol). Scion Instruments has designed GC solutions for each of these standard methods. This paper describes work conducted on the SCION Instruments 436 gas chromatograph to analyse biodiesel (B-100) in accordance with EN-14103. EN-14103 is used to verify that the ester content of Fatty Acid Methyl Esters (FAME) is greater than 90% and that the linolenic acid content is between 1 % (m/m) and 15 % (m/m) consistent with EN-14214 specifications.

This method is suitable for FAME which contains methyl esters between C14 and C24.

Biodiesel Chromatogram showing methyl esters between C14 and C24.

Fig.1 – Biodiesel Chromatogram

   
C16:0 Palmitic Acid
C16:1 Palmitoleic acid
C17:0 Heptadecanoic acid

(internal standard)

C18:0 Stearic acid
C18:1 Oleic acid
C18:2 Linoleic acid
C18:3 Linolenic acid
C20:0 Arachidic acid
C20:1 Gadoleic acid
C22:0 Behenic acid
C22:1 Erucic acid
C24:0 Lignoceric acid
C24:1 Nervonic acid

Table 1. Identification

Experimental

The SCION Biodiesel analyser for EN 14103 is based on our 436 GC platform, a split/splitless injector, a SCION WAXMS analytical column and an FID Detector. Analytical conditions for the EN 14103 analysis can be found in table 1. When the conditions outlined below are applied, a chromatogram is obtained, as in Figure 1.

Injector Split/Splitless @ 250°C
Column 30m x 0. 25 mm x 0. 25 μm

SCION WAXMS (SC32423)

Oven Program 210ºC Isothermal
Carrier Helium @ 12 psi (83 kPa)
Detector FID @ 250ºC
Inj. Volume 1µl
Software Compass CDS

Table 1. Analytical Conditions

Sample Preparation

Accurately weigh approximately 250 mg of sample in a 10 mL vial, then add 5 mL of methyl heptadecanoate solution (10 mg / mL) using a
pipette.

Calculations

The ester content (C), expressed as a mass fraction in percent, is calculated using the following formula:

Formula 1

Where:

ΣA → total peak area from C14:0 to C24:1
AEI → peak area of C17:0
CEI → is the concentration, in mg/ml, of the C17:0 solution
VEI → volume, in ml, of the C17:0 solution
m → mass, in mg, of the sample
The linolenic acid methyl ester content (L), expressed as a mass fraction in percent, is calculated using the following formula:

Formula 2

Where:

ΣA → total peak area from C14:0 to C24:1
AEI → peak area of C17:0
AL → peak area of C18:3

Results

The results of the biodiesel assay are stated in Table 3. The biodiesel sample tested was shown to be in accordance with the requirements
stated in EN 14214 (the method requirements: FAME content > 96.5 % (m/m) and linolenic acid content < 12 % (m/m)).

In order to verify the integrity of the system, repeatability was determined (n=15). See Table 4 and Figure 2.

A relative standard deviation of 0.21 % was achieved. Figure 2 shows the mass % results of the subsequent injections and the absolute
difference obtained compared to specification limits.

  Area (µV.min) Quantity (%m/m)
FAME 103139 96,6
Linolenic Acid 7599,2 7,1

Table 3. Analytical results Biodiesel Assay

  Quantity (%m/m) Quantity (%m/m)
Average 96,4 7,1
Standard Deviation 0,20 0,015
RSD (%) 0,21 0,21

Table 4. Repeatability Results

Red lines indicate the maximum and minimum allowed variation limits specified in the method.
Fig. 2 Repeatability figures. Red lines indicate the maximum and minimum allowed variation limits specified in the method.

Conclusion

This application note demonstrates the suitability of SCION Instruments Analyser for EN 14103, for the analysis of biodiesel. The repeatability data demonstrates good system integrity. The biodiesel sample tested in this application note fulfilled the requirements stated in EN 14214 Therefore, the system is well suited to the analysis of total FAME and Linolenic Acid Methyl Esters in Biodiesel According to EN 14103.

Download the Application Note

You can download the complete application note as a pdf: Determination of Total FAME and Linolenic Acid Methyl Esters in Biodiesel

SCION 436 GC

The SCION 436 GC was used to conduct this research. Find out more about the GC.

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