GB/T 32384-2015 Separation and determination of aromatic hydrocarbon components in middle distillates — Solid phase extraction-gas chromatography

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Card type: Test method

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

• Standard number: GB/T 32384—2015
• Chinese full name: Separation and determination of aromatic hydrocarbon components in middle distillates — Solid phase extraction-gas chromatography
• English name: Standard test method for separation and determination of aromatic fractions in middle distillates—Solid-phase extraction and gas chromatographic method
• Replacement relationship: not provided in the available source (the foreword only states that it was drafted in accordance with GB/T 1.1—2009, and does not mention replacing any standard)
• Publication/implementation: published on 2015-12-31, implemented on 2016-05-01
• Custodianship: Subcommittee on Petroleum Fuels and Lubricants of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280/SC1)
• Drafting organizations: responsible drafting by the Research Institute of Petroleum Processing, China Petroleum & Chemical Corporation; participating drafting by the Yanshan Branch, the Research Institute of the Qilu Branch, the University of Petroleum (Beijing), and the Beijing Research Institute of Chemical Industry
• Main drafters: Liu Zelong, Yang Tingting
• Method division: this standard is divided into Method One and Method Two

2. Scope of application and non-applicability

• Applicable: use solid phase extraction-gas chromatography to separate and determine aromatic hydrocarbon components, non-aromatic hydrocarbon components, and fatty acid methyl ester components in middle distillates (including diesel containing fatty acid methyl esters).
• Distillation range: middle distillates from 170 ℃ to 400 ℃, including diesel containing fatty acid methyl esters at a volume fraction less than 10%.
• Method One: applicable to middle distillates that do not contain fatty acid methyl esters.
• Method Two: applicable to diesel containing fatty acid methyl esters at a volume fraction less than 10%.
• Applicable content range: middle distillate samples with an aromatic hydrocarbon component mass fraction of 4% to 50%; diesel samples with a fatty acid methyl ester component volume fraction of 2% to 10%.
• Outside the above content range: determination is also possible, but precision data are not provided.
• Component assignment note: in Method One analysis, the aromatic hydrocarbons include thiophene-type sulfur-containing compounds, nitrogen-containing compounds, and oxygen-containing compounds; in Method Two analysis, nitrogen-containing compounds and oxygen-containing compounds are included in the fatty acid methyl ester components and may affect the results.
• Not applicable: no explicit non-applicability clauses are provided in the available source (apart from the scope definitions above).
• Safety warning: this standard does not address all safety issues involved; users should establish appropriate safety precautions before use and determine the applicability of relevant regulatory limitations.

3. Method principle

• Method One: add the sample dropwise onto a solid phase extraction column, elute with solvents of different polarities, and separate the aromatic hydrocarbon components and non-aromatic hydrocarbon components; add equal amounts of the same internal standard solution to the separated aromatic hydrocarbon component eluate and non-aromatic hydrocarbon component eluate, then introduce them into gas chromatography for analysis. Based on the peak areas of the aromatic hydrocarbon components and non-aromatic hydrocarbon components obtained by chromatographic analysis and the peak area of the internal standard peak, calculate the mass fractions of the aromatic hydrocarbon components and non-aromatic hydrocarbon components in the sample according to the formulas specified in this standard.
• Method Two: add the sample dropwise onto a solid phase extraction column, elute with solvents of different polarities, and separate the aromatic hydrocarbon components, non-aromatic hydrocarbon components, and fatty acid methyl ester components; add equal amounts of the same internal standard solution to the three eluates, then introduce them into gas chromatography for analysis. Based on the peak areas of the aromatic hydrocarbon components, non-aromatic hydrocarbon components, and fatty acid methyl ester components obtained by chromatographic analysis, the peak areas of each internal standard peak, and the correction factor for fatty acid methyl esters, calculate the mass fractions of the aromatic hydrocarbon components, non-aromatic hydrocarbon components, and fatty acid methyl ester components in the sample according to the formulas specified in this standard; based on the sample density, calculate the volume fraction of the fatty acid methyl ester components in the sample according to the formulas specified in this standard.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 6.1.1 Anhydrous ethanol: analytical reagent.
• 6.1.2 Dichloromethane: analytical reagent. Warning — toxic; harmful to humans if ingested or absorbed through the skin.
• 6.1.3 Benzene: analytical reagent. Warning — toxic; harmful to humans if ingested or absorbed through the skin.
• 6.1.4 n-Pentane: analytical reagent.
• 6.1.5 n-Hexane: analytical reagent.
• 6.1.6 n-Hexadecane: chromatographic grade.
• 6.1.7 C30 n-Alkanes: chromatographic grade.
• 6.1.8 C32 n-Alkanes: chromatographic grade.
• 6.1.9 Internal standard solution: C30 or C32 n-alkanes dissolved in n-hexane, at a mass concentration of 0.001 g/mL to 0.005 g/mL.
• 6.1.10 Pure biodiesel: biodiesel meeting the requirements of GB/T 20828.

4.2 Materials

• 6.2.1 Compressed air: purity not less than 99.9%. Warning — high-pressure gas; pay attention to safety.
• 6.2.2 Hydrogen: purity not less than 99.9%. Warning — high-pressure gas; extremely flammable.
• 6.2.3 Carrier gas: nitrogen or helium, purity not less than 99.99%. Warning — high-pressure gas; pay attention to safety.

4.3 Sample for determining the fatty acid methyl ester correction factor (6.3)

• Used to determine the response correction factor for fatty acid methyl esters and hydrocarbons, and to correct when calculating the fatty acid methyl ester content.
• Prepared with pure biodiesel and n-hexadecane: separately weigh pure biodiesel meeting the requirements of GB/T 20828 and n-hexadecane into a glass container; the mass ratio of pure biodiesel to n-hexadecane is about 1:1; add an appropriate amount of dichloromethane to dissolve, so that the sample mass fraction is about 1%.

4.4 Quality control check sample (Method One, 6.4)

• Used for routine monitoring of the gas chromatography system; through analysis of the quality control check sample, determine whether the gas chromatography measurement results are within the precision range.
• Prepared or purchased from the aromatic hydrocarbon components and non-aromatic hydrocarbon components separated by the chromatographic method in SH/T 0606—2005 Annex A (or the ASTM D2549 method).
• Preparation method: separately weigh the aromatic hydrocarbon components and non-aromatic hydrocarbon components separated by the chromatographic method in SH/T 0606—2005 Annex A (or the ASTM D2549 method), place them into two glass containers, add equal volumes of the same concentration of internal standard solution to each, and shake well; based on the weighed proportions of the aromatic hydrocarbon components and non-aromatic hydrocarbon components, the contents of the aromatic hydrocarbon components and non-aromatic hydrocarbon components in the quality control check sample can be determined.
• The aromatic hydrocarbon components and non-aromatic hydrocarbon components of the prepared quality control check sample should be similar in composition to the test sample.

4.5 Quality control check sample (Method Two, 6.5)

• Used for routine monitoring of the gas chromatography system; through analysis of the quality control check sample, determine whether the gas chromatography measurement results are within the precision range.
• Prepared from the aromatic hydrocarbon components, non-aromatic hydrocarbon components, and pure biodiesel separated by the chromatographic method in SH/T 0606—2005 Annex A (or the ASTM D2549 method).
• Preparation method: separately weigh the aromatic hydrocarbon components, non-aromatic hydrocarbon components, and pure biodiesel separated by the chromatographic method in SH/T 0606—2005 Annex A (or the ASTM D2549 method), place them into three glass containers, add equal volumes of the same concentration of internal standard solution to each, and shake well; based on the weighed proportions of the aromatic hydrocarbon components, non-aromatic hydrocarbon components, and pure biodiesel, the contents of the aromatic hydrocarbon components, non-aromatic hydrocarbon components, and fatty acid methyl ester components in the quality control check sample can be determined.
• The contents of the aromatic hydrocarbon components, non-aromatic hydrocarbon components, and fatty acid methyl ester components of the prepared quality control check sample should be similar in composition to the test sample.

4.6 Middle distillate reference sample (6.6)

• A middle distillate oil with known contents of non-aromatic hydrocarbons and aromatic hydrocarbon components; the contents of non-aromatic hydrocarbons and aromatic hydrocarbon components are obtained by the SH/T 0606—2005 method or the ASTM D2549 method.

4.7 Reference sample of diesel containing fatty acid methyl esters (6.7)

• Diesel containing fatty acid methyl esters with known contents of non-aromatic hydrocarbons, aromatic hydrocarbons, and fatty acid methyl ester components.
• Prepared from middle distillate oil with known contents of non-aromatic hydrocarbons and aromatic hydrocarbon components and pure biodiesel.
• The fatty acid methyl ester component content of the prepared reference sample of diesel containing fatty acid methyl esters should be similar in composition to the test sample.

5. Instruments and equipment

• 5.1 Solid phase extraction separation system
  • 5.1.1 Solid phase extraction column: as shown in Figure 1. Its function is to effectively separate the aromatic hydrocarbon components and non-aromatic hydrocarbon components in middle distillates, as well as the aromatic hydrocarbon components, non-aromatic hydrocarbons, and fatty acid methyl ester components in diesel containing fatty acid methyl esters. The solid phase extraction columns used in 9.1 and 9.2 are 3 mL solid phase extraction columns packed with about 1.5 g of stationary phase.
    • Figure 1 composition: 1—— sample inlet; 2—— adapter; 3—— extraction column; 4—— frit; 5—— stationary phase; 6—— sample outlet.
    • Note 1: any solid phase extraction column meeting the requirements of this standard may be used.
    • Note 2: the solid phase extraction column should be stored in a desiccator.
    • Note 3: the solid phase extraction column must not be reused.
  • 5.1.2 Conical flask: 25 mL.
  • 5.1.3 Syringe: 2 mL, 0.25 mL.
  • 5.1.4 Pipette: 1 mL.
• 5.2 Gas chromatography analysis system
  • 5.2.1 Gas chromatograph: should include a vaporization chamber, a temperature-controlled column oven, a chromatographic column, a flame ionization detector, and a chromatography workstation. Any gas chromatograph meeting the performance and parameter requirements listed in Table 1 may be used.
  • 5.2.2 Chromatographic column: non-polar quartz capillary chromatographic column, allowing the sample to be separated according to boiling point.
  • 5.2.3 Injection system: can introduce the sample solution into the chromatographic inlet; a microsyringe and an autosampler may be used.
  • 5.2.4 Vaporization system: split or splitless injection may be used, but the actual amount of sample entering the chromatographic system must meet the requirements of column efficiency and detector linear range.
  • 5.2.5 Detector: a flame ionization detector is used to quantitatively detect the components flowing out of the chromatographic column and should have sufficient sensitivity and stability.
  • 5.2.6 Chromatography workstation: can display the acquired chromatogram, measure the peak areas of chromatographic peaks, and perform necessary manual integration processing.

6. Recommended operating conditions

Table 1 Typical chromatographic operating parameters (a):

• Chromatographic column: quartz capillary chromatographic column
  • Dimensions: column length 30 m, internal diameter 0.25 mm, film thickness 0.25 μm
  • Stationary phase: non-polar, such as 100% dimethylpolysiloxane or 5% phenyl-methylpolysiloxane
• Temperature
  • Vaporization chamber/℃: 300
  • Detector/℃: 350
  • Chromatographic column: 60 ℃ hold 2 min, then raise to 300 ℃ at 40 ℃/min, hold 5 min
• Carrier gas: helium or nitrogen
  • Column flow rate/(mL/min): approximately 1.0
  • Split ratio: approximately 20:1
• Detector: hydrogen flame ionization detector
• Sample amount/μL: approximately 0.5

a: The instrument parameters given in the table are optional parameter conditions. A chromatographic column of 15 m to 30 m column length and inner diameter 0.15 mm to 0.32 mm may be used, and an appropriate column temperature program may be selected, as long as it can ensure complete separation of the solvent, sample, and internal standard in the analyzed sample.

7. Sampling and sample preparation

• Sampling: Unless otherwise specified, sampling shall be carried out in accordance with GB/T 4756. Samples shall be stored in sealed containers.
• Sample preparation: not provided in the available source as a separate sample preparation clause (the sample is directly drawn with a 0.25 mL syringe in accordance with 9.1.1.2 / 9.2.1.2, and about 0.1 mL of sample is dropped into the solid-phase extraction column).

8. Analytical procedure

8.1 Preparation of the gas chromatograph and establishment of conditions

• 8.1 In general, when the gas chromatograph is running continuously, no other preparation work is required before analyzing samples. If the instrument has just been started, the instrument status shall be checked in accordance with this standard and the instrument manual to ensure that the instrument is stable.
• 8.2 Check the separation effect of the solvent, sample, and internal standard by using quality control check samples (6.4 and 6.5). If necessary, adjust the column temperature program so that the three are completely separated.
• 8.3 Determine the quality control check samples (6.4 and 6.5) in accordance with 9.1 or 9.2 to obtain the contents of aromatic components, non-aromatic components, and fatty acid methyl ester components, and compare them with the actual values to determine the accuracy of the gas chromatographic determination of the contents of aromatic, non-aromatic, and fatty acid methyl ester components.

8.2 Method 1: Determination of middle distillate samples not containing fatty acid methyl esters (9.1)

8.2.1 Solid-phase extraction separation procedure

• 9.1.1.1 Take one solid-phase extraction column and wet the stationary phase with 0.5 mL n-pentane.
• 9.1.1.2 Use a 0.25 mL syringe to draw about 0.1 mL of sample and drop it onto the upper frit in the solid-phase extraction column, where it is completely adsorbed.
• 9.1.1.3 Place a 25 mL conical flask below the sample outlet of the solid-phase extraction column. Sequentially rinse the stationary phase with 2 mL n-pentane and 0.5 mL of a mixed solution of dichloromethane and ethanol in a volume ratio of 5:1 to elute the adsorbed non-aromatic components, with an elution rate of approximately 2 mL/min. The eluate of the non-aromatic components is collected in this 25 mL conical flask. When the added 0.5 mL of the mixed solution of dichloromethane and ethanol in a volume ratio of 5:1 has just completely entered the stationary phase, replace with another 25 mL conical flask, then rinse the stationary phase with 2 mL of the mixed solution of dichloromethane and ethanol in a volume ratio of 5:1 to elute the adsorbed aromatic components, with an elution rate of approximately 2 mL/min. The eluate of the aromatic components is collected in this 25 mL conical flask.
  • Note: A syringe may be connected to the adapter on the upper part of the solid-phase extraction column to apply pressure in order to control the solvent outflow rate.
• 9.1.1.4 Use a pipette to respectively add 1.00 mL of internal standard solution to the 25 mL conical flasks containing the eluates of the aromatic components and non-aromatic components, and shake well.

8.2.2 Gas chromatographic analysis

• 9.1.2.1 Preparation of the gas chromatograph: Before analyzing samples, the instrument shall be run blank once according to the analytical procedure to remove residual substances in the gas chromatograph.
• 9.1.2.2 Subject the 9.1.1.4 eluates of the aromatic components and non-aromatic components to which the internal standard has been added to gas chromatographic analysis separately to obtain the chromatograms shown in Figure 2. Based on the peak areas of the aromatic peaks and internal standard peaks in the chromatogram of the aromatic solution and the peak areas of the non-aromatic peaks and internal standard peaks in the chromatogram of the non-aromatic solution obtained by integration with the chromatography workstation, calculate the mass fractions of the aromatic components and non-aromatic components according to formula (1) and formula (2).
  • Note: Check the integration status of the chromatograms by the chromatography workstation to confirm that all chromatographic peaks have been reasonably integrated (perpendicular drop integration). If unreasonable, the integration parameters may be changed or the manual integration function may be used for re-integration.
• Figure 2: Chromatogram of aromatic and non-aromatic components of a middle distillate sample.

8.3 Method 2: Determination of diesel samples containing fatty acid methyl esters (9.2)

8.3.1 Solid-phase extraction separation procedure

• 9.2.1.1 Take one solid-phase extraction column and wet the stationary phase with 0.5 mL n-pentane.
• 9.2.1.2 Use a 0.25 mL syringe to draw about 0.1 mL of sample and drop it onto the upper frit in the solid-phase extraction column, where it is completely adsorbed.
• 9.2.1.3 Place the first 25 mL conical flask below the sample outlet of the solid-phase extraction column. Sequentially rinse the stationary phase with 2 mL n-pentane and 0.5 mL of a mixed solution of dichloromethane and n-pentane in a volume ratio of 1:1 to elute the adsorbed non-aromatic components, with an elution rate of approximately 2 mL/min. The eluate of the non-aromatic components is collected in the first 25 mL conical flask. When the added 0.5 mL of the mixed solution of dichloromethane and n-pentane in a volume ratio of 1:1 has just completely entered the stationary phase, replace with the second 25 mL conical flask, then rinse the stationary phase with 2 mL of the mixed solution of dichloromethane and n-pentane in a volume ratio of 1:1 to elute the adsorbed aromatic components, with an elution rate of approximately 2 mL/min. The eluate of the aromatic components is collected in the second 25 mL conical flask. When the added 2 mL of the mixed solution of dichloromethane and n-pentane in a volume ratio of 1:1 has just completely entered the stationary phase, replace with the third 25 mL conical flask, and finally rinse with 6 mL of a mixed solution of benzene and ethanol in a volume ratio of 1:1 to elute the adsorbed fatty acid methyl ester components, with an elution rate of approximately 2 mL/min. The eluate of the fatty acid methyl ester components is collected in the third 25 mL conical flask.
  • Note: A syringe may be connected to the adapter on the upper part of the solid-phase extraction column to apply pressure in order to control the solvent outflow rate.
• 9.2.1.4 Use a pipette to respectively add 1.00 mL of internal standard solution to the three 25 mL conical flasks containing the eluates of the aromatic components, non-aromatic components, and fatty acid methyl ester components, and shake well.

8.3.2 Gas chromatographic analysis

• 9.2.2.1 Prepare the gas chromatograph in accordance with 9.1.2.1.
• 9.2.2.2 Subject the sample for determining the correction factor of fatty acid methyl esters in accordance with 6.3 to gas chromatographic analysis to obtain the chromatogram shown in Figure 3. Based on the peak areas of the fatty acid methyl esters and n-hexadecane, and the weighed amounts of pure biodiesel and n-hexadecane used in preparing the sample, calculate the correction factor B for fatty acid methyl esters according to formula (3).
• 9.2.2.3 Subject the solutions of the aromatic components, non-aromatic components, and fatty acid methyl ester components separated in accordance with 9.2.1 and to which the internal standard has been added to gas chromatographic analysis separately to obtain the chromatograms shown in Figure 4. Based on the peak areas of the aromatic peaks and internal standard peaks in the chromatogram of the aromatic solution, the peak areas of the non-aromatic peaks and internal standard peaks in the chromatogram of the non-aromatic solution, and the peak areas of the fatty acid methyl ester peaks and internal standard peaks in the chromatogram of the fatty acid methyl ester solution obtained by integration with the chromatography workstation, calculate the mass fractions of the aromatic components, non-aromatic components, and fatty acid methyl ester components of the sample according to formula (4), formula (5), and formula (6). Based on the density of the sample, the volume fraction of the fatty acid methyl ester components in the sample can be calculated according to formula (7).
  • Note: Check the integration status of the chromatograms by the chromatography workstation to confirm that all chromatographic peaks have been reasonably integrated (perpendicular drop integration). If unreasonable, the integration parameters may be changed or the manual integration function may be used for re-integration.
• Figure 3: Chromatogram of the sample for determining the correction factor of fatty acid methyl esters.
• Figure 4: Chromatogram of aromatic, non-aromatic, and fatty acid methyl ester components of a diesel sample containing fatty acid methyl esters.

8.4 Quality control check (Chapter 11)

• 11.1 Gas chromatographic analysis quality control check: After the instrument has been running for a period of time (generally 3 months) or after the instrument system has been changed, the quality control check samples 6.4 or 6.5 shall be analyzed in accordance with 9.1.2 or 9.2.2. The difference between the results of the quality control check samples and the actual values shall meet the reproducibility requirements specified in the method. If the determination results exceed the requirements, the source of error shall be determined.
• 11.2 Solid-phase extraction separation quality control check: After analysis for a period of time (generally 3 months), a middle distillate reference sample with known contents of aromatic and non-aromatic components (6.6) shall be analyzed once in accordance with 9.1, or a fatty acid methyl ester-containing diesel reference sample with known contents of aromatic, non-aromatic, and fatty acid methyl ester components (6.7) shall be analyzed once in accordance with 9.2. The difference between the analysis results and the actual values shall meet the reproducibility requirements specified in this method. If the determination results exceed the requirements, the source of error shall be determined. If necessary, the separation efficiency of the solid-phase extraction column may be determined by the SH/T 0606—2005 method.
  • Note: The mass fraction of aromatic content in the non-aromatic components and the mass fraction of non-aromatic content in the aromatic components shall both be less than 5%.

9. Qualitative and quantitative determination and calculation formulas

9.1 Method 1 (10.1)

• 10.1.1 The mass fraction of aromatic components in the sample X1 is calculated according to formula (1): X1 = [ (Aa/Ana) / ( As/Ans + Aa/Ana ) ] × 100%
• 10.1.2 The mass fraction of non-aromatic components in the sample X2 is calculated according to formula (2): X2 = [ (As/Ans) / ( As/Ans + Aa/Ana ) ] × 100%
• Where:
  • Aa —— the total peak area of aromatic hydrocarbons in the chromatogram of the aromatic components;
  • Ana ——peak area of the internal standard in the chromatogram of the aromatic component;
  • As ——total peak area of non-aromatic components in the chromatogram of the non-aromatic component;
  • Ans ——peak area of the internal standard in the chromatogram of the non-aromatic component.

9.2 Method Two (10.2)

• 10.2.1 The correction factor for fatty acid methyl esters B is calculated according to formula (3): B = (M1/M2) × (Sw/SN16)
  • Where:
    • M1 ——the amount of pure biodiesel added when preparing the sample for determining the fatty acid methyl ester correction factor, in grams (g);
    • M2 ——the amount of n-hexadecane added when preparing the sample for determining the fatty acid methyl ester correction factor, in grams (g);
    • Sw ——total peak area of fatty acid methyl esters in the chromatogram of the sample for determining the fatty acid methyl ester correction factor;
    • SN16 ——peak area of n-hexadecane in the chromatogram of the sample for determining the fatty acid methyl ester correction factor.
• 10.2.2 The mass fraction of aromatic components in diesel samples containing fatty acid methyl esters X3 is calculated according to formula (4): X3 = [ (Aa/Ana) / ( As/Ans + Aa/Ana + (Aw×B)/Anw ) ] × 100%
• 10.2.3 The mass fraction of non-aromatic components in diesel samples containing fatty acid methyl esters X4 is calculated according to formula (5): X4 = [ (As/Ans) / ( As/Ans + Aa/Ana + (Aw×B)/Anw ) ] × 100%
• 10.2.4 The mass fraction of fatty acid methyl esters in diesel samples containing fatty acid methyl esters X5 is calculated according to formula (6): X5 = [ ( (Aw×B)/Anw ) / ( As/Ans + Aa/Ana + (Aw×B)/Anw ) ] × 100%
  • Where:
    • Aw ——total peak area of fatty acid methyl esters in the chromatogram of fatty acid methyl esters;
    • Anw ——peak area of the internal standard in the chromatogram of fatty acid methyl esters;
    • B ——correction factor for fatty acid methyl esters.
• 10.2.5 The volume fraction of fatty acid methyl esters in diesel samples containing fatty acid methyl esters X6 is calculated according to formula (7): X6 = X5 × (d2/d1)
  • Where:
    • d1 ——the density of fatty acid methyl esters at 20 ℃, d1 = 880.0 kg/m³;
    • d2 ——the density of the sample at 20 ℃, in kilograms per cubic meter (kg/m³), determined using the SH/T 0604 method.
  • Note: The density of fatty acid methyl esters at 20 ℃ uses a fixed value of 880.0 kg/m³.

10. Precision

10.1 Precision (12.1)

• 12.1.1 The precision for the determination of aromatic and non-aromatic components established by this method was obtained from collaborative tests in 5 laboratories on 9 samples of middle distillates with aromatic content ranging from 4% to 50%; the precision for the determination of fatty acid methyl ester content in diesel samples containing fatty acid methyl esters was obtained from collaborative tests on 10 diesel samples from different biodiesel sources with volume fractions of fatty acid methyl esters ranging from 2% to 10%; the collaborative test results were statistically analyzed and calculated in accordance with the GB/T 6683 method. The reliability of the test results is judged according to the following provisions (95% confidence level).
• 12.1.2 Repeatability: The difference between two results obtained by the same operator using the same instrument on the same sample for repeated determinations shall not exceed the repeatability values specified in Table 2 and Table 3.
• 12.1.3 Reproducibility: The difference between two single and independent results obtained by different operators in different laboratories using different instruments on the same sample shall not exceed the reproducibility values specified in Table 2 and Table 3.

Table 2 Precision for the determination of aromatic and non-aromatic components (% (mass fraction))

Note: X is the average of the two results being compared, % (mass fraction).

Table 3 Precision for the determination of fatty acid methyl esters (% (mass fraction or volume fraction))

Note 1: X is the average of the two results being compared, % (mass fraction or volume fraction). Note 2: This precision was determined by collaborative tests in 4 laboratories and is for reference.

10.2 Bias (12.2)

• Since there is no reference material for determining bias, the bias of this method cannot be determined.

11. Report

• For middle distillate samples that do not contain fatty acid methyl esters, the report includes the mass fractions of aromatic components and non-aromatic components, with results rounded to 0.1%.
• For diesel samples containing fatty acid methyl esters, the report includes the mass fractions of aromatic components and non-aromatic components and the mass fraction or volume fraction of the fatty acid methyl ester component. Results are rounded to 0.1%.

12. Normative References

• GB/T 1885 Petroleum measurement tables (GB/T 1885—1998, eqv ISO 91-2:1991)
• GB/T 4756 Manual sampling of petroleum liquids (GB/T 4756—1998, eqv ISO 3170:1988)
• GB/T 6683 Determination of precision data for test methods of petroleum products
• GB/T 20828 Biodiesel for blending with diesel engine fuels (BD100)
• SH/T 0604 Determination of density of crude oil and petroleum products (U oscillating U-tube method) (SH/T 0604—2000, eqv ISO 12185:1996)
• SH/T 0606—2005 Determination of hydrocarbon types in middle distillates (mass spectrometry method)
• ASTM D2549 Test method for separation of aromatic and non-aromatic components of high-boiling petroleum products by elution chromatography (Test method for separation of representative aromatics and nonaromatics of high-boiling oils by elution chromatography)
• Foreword reference: GB/T 1.1—2009

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