NB/SH/T 0831-2010 Determination of fatty acid methyl esters and linolenic acid methyl ester content in biodiesel — Gas chromatography

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Card type: Test method

1. Method number / full title / English title / replacement relationship

• Standard number: NB/SH/T 0831-2010
• Chinese title: Determination of fatty acid methyl esters and linolenic acid methyl ester content in biodiesel — Gas chromatography
• English title: Test method for determination of fatty acid methyl esters and linolenic acid methyl ester contents in biodiesel by gas chromatography
• Replacement relationship: not provided in the available source (the foreword does not mention replacement of any standard)
• Adoption relationship: modified adoption of the European Standard EN 14103:2003 "Animal and vegetable fats and oils derivatives — Fatty acid methyl esters — Determination of ester content and linolenic acid methyl ester content", redrafted according to EN 14103:2003
• Main differences from EN 14103:2003 (foreword):
  • The corresponding Chinese national standards are cited in the normative references
  • Added column conditions using argon as carrier gas (requires confirmation against the source standard (source-text extraction): the original text reads "[garbled gas name]", suspected to be "argon")
  • Corrected the 8.2.1 formula (2) in EN 14103:2003
  • Moved the content of Annex A in EN 14103:2003 into Table 1 and Figures 1 and 2 of the main text, and made Annex B in EN 14103:2003 into Annex A; added a structural difference comparison table as Annex B
• Publication/implementation: published on 2010-05-01, implemented on 2010-10-01
• Issuing authority: National Energy Administration
• Drafting organization: Sinopec Research Institute of Petroleum Processing
• Main drafter: Li Changxiu
• Custodianship: Subcommittee on Petroleum Fuels and Lubricants of the National Technical Committee for Standardization of Petroleum Products and Lubricants
• Proposed by: China Petrochemical Corporation

2. Scope of application and non-applicability

• 1.1 specifies a method for determining the content of fatty acid methyl esters (FAME) in biodiesel used as pure biofuel or as a blending component of diesel fuel, and the content of linolenic acid methyl ester contained therein.
• 1.2 is used to determine the total content of fatty acid methyl esters with a mass fraction greater than 90%; the determination range for the mass fraction of linolenic acid methyl ester is 1%~15%.
• 1.3 is applicable to the determination of the content of fatty acid methyl esters from C14 to C24 (requires confirmation against the source standard (source-text extraction): the original text reads "Cj4 to C2", inferred from the context and the later C14~C24).
• Non-applicability: no explicit non-applicability clause is provided in the available source.

3. Method principle

A test sample to which a certain amount of methyl heptadecanoate internal standard has been added in advance is introduced into a gas chromatography system. The fatty acid methyl esters in the sample are separated on a strongly polar capillary column with polyethylene glycol as the stationary phase, detected with a flame ionization detector, and quantified by the internal standard method to obtain the content of fatty acid methyl esters and the content of linolenic acid methyl ester.

4. Reagents and materials (purity / preparation)

• 4.1 n-Heptane: analytical reagent.
• 4.2 Methyl heptadecanoate: purity greater than 99%.
• 4.3 Methyl heptadecanoate solution: mass concentration 10 mg/mL. Weigh approximately 500 mg of methyl heptadecanoate (see 4.2) into a 50 mL volumetric flask (see 5.4), accurate to 0.1 mg, and dilute to the mark with n-heptane (see 4.1).

5. Apparatus and equipment

• 5.1 Gas chromatograph system, composed of the following components:
  • 5.1.1 Gas chromatograph: the instrument configuration shall meet the conditions specified in Table 1.
  • 5.1.2 Chromatographic column: a column coated with polyethylene glycol chromatographic stationary phase (Carbowax 20M, Dbwax, Cpwax, etc.), with a column length of 30 m, an internal diameter of 0.32 mm or 0.25 mm, and a film thickness of 0.25 μm can achieve good separation. Other columns with the same or better column efficiency or selectivity may also be used.
• 5.2 Electronic data acquisition system: an integrator or computer capable of real-time plotting and chromatographic data conversion, and automatic integration to measure the area and retention time of chromatographic peaks.
• 5.3 Screw-cap vial with polytetrafluoroethylene liner: 10 mL.
• 5.4 Volumetric flask: 50 mL.
• 5.5 Pipette: 5 mL, accurate to 0.02 mL.

(Note: the original text at numbers 5.3~5.5 has severe source-text extraction noise; the numbers are inferred from the context and require confirmation against the source standard (source-text extraction))

6. Recommended operating conditions

Table 1 Chromatographic analysis conditions (the original table source-text extraction has severe noise; the following is the identifiable content and requires confirmation against the source standard (source-text extraction)):

• 7.2.2 The chromatographic conditions (including injection volume, column temperature, carrier gas pressure and split ratio, etc.) should be appropriately adjusted to ensure that methyl lignocerate (C24:0) can elute as a peak.
• 7.2.3 Integration of chromatographic peaks should, as far as possible, include all chromatographic peaks from the peak of methyl myristate (C14) to the peak of C24, including small peaks among them, in the integration result.

7. Sampling and sample preparation

• Sampling: sample according to the method of GB/T 4756.
• Sample preparation (7.1): weigh approximately 250 mg of test sample into a 10 mL screw-cap vial (see 5.3), accurate to 0.1 mg, and add 5 mL of methyl heptadecanoate solution (see 4.3) with a pipette (see 5.5).

8. Analytical procedure

• 7.2 Chromatographic analysis
  • 7.2.1 Referring to the principles for selecting chromatographic conditions in GB/T 17377, perform the analysis according to the chromatographic conditions described in Table 1. Typical chromatograms are shown in Figure 1 and Figure 2.
  • 7.2.2 The chromatographic conditions (including injection volume, column temperature, carrier gas pressure and split ratio, etc.) should be appropriately adjusted to ensure that methyl lignocerate (C24:0) can elute as a peak.
  • 7.2.3 Integration of chromatographic peaks should, as far as possible, include all chromatographic peaks from the peak of methyl myristate (C14) to the peak of C24, including small peaks among them, in the integration result.
• Note: the sample may contain chromatographic solvent (requires confirmation against the source standard (source-text extraction): the original text reads "[garbled wording about possible chromatographic solvent in the sample]").

9. Qualitative and quantitative determination and calculation formulas

8.1 Fatty acid methyl ester content

8.1.1 Fatty acid methyl ester content C, calculated according to formula (1):

C = (ΣA − A_internal standard) / A_internal standard × C_internal standard × V_internal standard / m × 100 ......(1)

Where:

• ΣA—— total area of all chromatographic peaks from C14 to C24;
• A_internal standard — the chromatographic peak area of methyl heptadecanoate;
• C_internal standard — the mass concentration of methyl heptadecanoate solution (4.3), mg/mL;
• V_internal standard — the volume of methyl heptadecanoate solution (4.3), mL;
• m—— sample mass, mg.

(Note: formula source-text extraction has severe noise; the above is reconstructed from the context and requires confirmation against the source standard (source-text extraction))

• Note 1: For fatty acid methyl esters derived from vegetable oils, when strict accurate quantification is not required, the area normalization result may also be used directly to represent the mass fraction of the components.
• Note 2: For a given sample, if the average of two determination results exceeds 100.2%, this measured value should be discarded, and the test conditions and whether the purity of the internal standard meets the requirements should be checked at the same time.

8.1.2 Report the result to one decimal place.

8.2 Determination of linolenic acid methyl ester content

8.2.1 Linolenic acid methyl ester content C_linolenic acid, expressed as the mass fraction of linolenic acid methyl ester content in the sample (%), calculated according to formula (2):

C_linolenic acid = A_linolenic acid / ΣA × C ......(2)

Where:

• ΣA—— total area of all chromatographic peaks from C14 to C24;
• A_internal standard — the chromatographic peak area of methyl heptadecanoate (the variable description of the original formula (2) includes this item; requires confirmation against the source standard (source-text extraction));
• A_linolenic acid — the chromatographic peak area of linolenic acid methyl ester;
• C—— the mass fraction of fatty acid methyl ester content in the sample calculated from formula (1), %.

Report the result to one decimal place.

Figure 1 Typical chromatogram of rapeseed oil biodiesel (peak assignment)

1— Methyl myristate (C14); 2— Methyl palmitate (C16); 3— Methyl palmitoleate; 4— Methyl heptadecanoate (internal standard); 5— Methyl stearate (C18); 6— Methyl oleate (C18:1); 7— Methyl linoleate (C18:2); 8— Methyl linolenate (C18:3); 9— Methyl arachidate (C20); 10— Methyl gadoleate (C20:1); 11— Methyl behenate (C22); 12— Methyl erucate (C22:1); 13— Methyl lignocerate (C24:0); 14— Methyl nervonate (C24:1).

(Note: The correspondence between peak numbers and names source-text extraction has severe noise, requires confirmation against the source standard (source-text extraction))

10. Precision

In the year 2000, an interlaboratory precision test was conducted with the participation of 11 laboratories. Each sample was determined twice. The statistical results are shown in Annex A. The reliability of the test results shall be judged according to the following provisions (95% confidence level).

9.1 Repeatability

The difference between two determination results for the same sample obtained by the same laboratory, the same operator, using the same instrument and equipment, under the same experimental conditions shall not exceed the value in Table 2.

Table 2 Repeatability:

9.2 Reproducibility

The difference between two independent determination results for the same sample obtained by different laboratories, different operators, using different instruments shall not exceed the value in Table 3.

Table 3 Reproducibility:

Note: X is the average of two independent determination results.

Annex A (Informative Annex) Interlaboratory Test Results

This test involved the analysis results of 5 countries and 11 laboratories in Europe for 5 samples.

• Sample 1: fatty acid methyl esters prepared from rapeseed oil and sunflower seed oil;
• Sample 2: fatty acid methyl esters prepared from sunflower seed oil;
• Sample 3: prepared by adding a small amount of rapeseed oil to fatty acid methyl esters prepared from rapeseed oil;
• Sample 4: fatty acid methyl esters prepared from rapeseed oil;
• Sample 5: prepared by adding a small amount of rapeseed oil to fatty acid methyl esters prepared from rapeseed oil.

This test project was organized by the CEN TC 307/WG1 working group in the year 2000. The test results obtained were statistically analyzed in accordance with the requirements of ISO 4259. The precision data obtained are shown in Table A.1 and Table A.2.

Table A.1 Mass fraction of fatty acid methyl esters (source-text extraction has severe noise, some data require confirmation against the source standard (source-text extraction)):

(Note: The correspondence between data columns and samples in Table A.1 source-text extraction has severe misalignment, requires confirmation against the source standard (source-text extraction))

Table A.2 Mass fraction of methyl linolenate (source-text extraction has severe noise, requires confirmation against the source standard (source-text extraction)):

(Note: The correspondence between data columns and samples in Table A.2 source-text extraction has severe misalignment, requires confirmation against the source standard (source-text extraction))

Annex B (Informative Annex) Comparison of Clause Numbers between This Standard and EN 14103:2003

Table B.1 provides a comparison list of clause numbers between this standard and EN 14103:2003. Except for the clause numbers listed in the comparison table, the other clauses of this standard are identical in clause number and correspond in content to those of EN 14103:2003.

(Note: The specific comparison content of Table B.1 source-text extraction is severely missing, requires confirmation against the source standard (source-text extraction))

11. Report

The report shall include the following contents:

• Detailed qualitative information of the sample;
• Sampling method used;
• Analysis method and standard number;
• Operational details not listed in this standard, and other factors that may affect the analysis results;
• Determination results; if repeated determinations were performed, report the final result.

12. Normative References

• GB/T 4756 Petroleum liquids — Manual sampling (GB/T 4756-1998, eqv ISO 3170:1988)
• GB/T 17377 Animal and vegetable fats and oils — Gas chromatographic analysis of fatty acid methyl esters (GB/T 17377-1998, eqv ISO 5508:1990)
• ISO 4259 Petroleum products — Determination of precision of test methods

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Reference Q&A