GB/T 30519-2024 Determination of hydrocarbon group composition and benzene content in light petroleum distillates and products—Multidimensional gas chromatography

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Incomplete source card: Sections 12, 13, 14 are absent from the available source. Only available content is translated; source completion is pending.

Card type: Test method

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

• Standard number: GB/T 30519—2024
• Chinese full title: Determination of hydrocarbon group composition and benzene content in light petroleum distillates and products—Multidimensional gas chromatography
• English title: Determination of hydrocarbon types and benzene content in light petroleum distillates and products—Multidimensional gas chromatography method
• Replacement relationship: replaces GB/T 30519—2014; this document was first issued in 2014, and this is the first revision.
• Main technical changes compared with the 2014 edition (foreword): a) deleted the method application (see Chapter 5 of the 2014 edition); b) changed the component table of the system verification sample (see 7.3, 8.2 and 8.3 of the 2014 edition); c) added the composition of a typical system verification sample containing ethanol (see 7.3); d) changed the average mass correction factors of each hydrocarbon group component (see Table 8, Table 7 of the 2014 edition); e) changed the weighted relative density of each hydrocarbon group component at 20 ℃ (see Table 9, Table 8 of the 2014 edition); f) changed the description of quality control sample development (see Chapter 11, Chapter 11 of the 2014 edition); g) changed the average mass correction factors of oxygen-containing compounds (see Table A.1, Table A.1 of the 2014 edition); h) changed the relative density of oxygen-containing compounds at 20 ℃ (see Table A.2, Table A.2 of the 2014 edition).
• Proposed and administered by: National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280).
• Publication/implementation: published on 2024-09-29, implemented on 2025-04-01.
• Drafting units (listed in the original text): Sinopec Research Institute of Petroleum Processing Co., Ltd., Petrochemical Research Institute of PetroChina Company Limited, China Automotive Technology and Research Center Co., Ltd., Beijing Yanshan Branch of China Petroleum & Chemical Corporation, Shenzhen Institute of Metrology and Quality Inspection, Guangzhou Customs Technology Center, Jinan Yusong Experimental Equipment Co., Ltd., Beijing Petroleum Product Quality Supervision and Inspection Center, Beijing Yixingyuan Petrochemical Technology Co., Ltd., Guizhou Institute of Product Quality Inspection and Testing.
• Main drafters (listed in the original text): Xu Guangtong, Shi Junge, Shi Yanqiang, Cao Xiaona, Zheng Yu, Chen Fei, Zhang Xin, Zhao Guoqi, Zhao Yan, Tan Zhiyi, Wang Shoucheng, Zhang Hailei, Xiao Jun, Li Jian, Li Xiaoyun.

2. Scope of application and non-applicability

• Applicable to: determination of olefins, aromatics and other hydrocarbon group composition and benzene content in light petroleum distillates and products by multidimensional gas chromatography.
• Applicable objects: light petroleum distillates and products with a final boiling point not higher than 215 ℃ (such as gasoline, gasoline blending components, solvent naphtha, etc.).
• Determination concentration range:
  • Olefins: volume fraction 0.5%~70% (mass fraction 0.4%~64%);
  • Aromatics: volume fraction 1%~80% (mass fraction 1.2%~92%);
  • Benzene: volume fraction 0.2%~10% (mass fraction 0.2%~12%).
• Outside the above ranges: when measuring samples whose content exceeds the above ranges, the precision has not been established.
• Also applicable to: gasoline products with a final boiling point not higher than 215 ℃ obtained from other unconventional crude oils such as shale or oil sands, or hydrocarbon fuels synthesized from non-petroleum mineral fuels such as Fischer-Tropsch synthetic oil, etc., but the precision has not been established.
• Oxygen-containing compound situation: motor gasoline often contains ether or alcohol oxygen-containing compounds, and multiple types may coexist; ethers elute together with olefins, and alcohols elute together with C7+ aromatics; for gasoline samples containing oxygen-containing compounds, use other test methods (such as NB/SH/T 0663) to determine the type and content of oxygen-containing compounds, and make necessary corrections to the hydrocarbon group composition results according to Annex A.
• Not applicable to: determination of individual component contents in each hydrocarbon group other than benzene.

3. Method principle

A certain amount of sample is directly injected into a gas chromatograph. After separation, each hydrocarbon group component enters a hydrogen flame ionization detector (FID) for detection, obtaining the chromatographic peak area of each hydrocarbon group component. A reference sample is used to determine the retention time of each hydrocarbon group component, and a corrected area normalization method is used for quantification to calculate the volume fraction or mass fraction of each hydrocarbon group component in the test sample. The analysis principle is shown in Figure 1, and the schematic diagram of the gas chromatograph and separation system is shown in Figure 2. For some light solvent naphtha products, if the olefin content does not need to be determined, the sample does not need to pass through the olefin trap after injection.

4. Reagents and materials (purity / preparation)

• 7.1 Component reagents (all analytical grade):
  • 7.1.1 n-pentane; 7.1.2 n-hexane; 7.1.3 cyclohexane; 7.1.4 methylcyclohexane; 7.1.5 n-heptane; 7.1.6 isooctane; 7.1.7 n-octane; 7.1.8 n-nonane; 7.1.9 n-decane; 7.1.10 n-undecane; 7.1.11 n-dodecane; 7.1.12 1- pentene; 7.1.13 1- hexene; 7.1.14 cyclohexene; 7.1.15 1- heptene; 7.1.16 1- octene; 7.1.17 1- nonene; 7.1.18 1- decene; 7.1.19 1- undecene; 7.1.20 benzene; 7.1.21 toluene; 7.1.22 mixed xylene; 7.1.23 ethylbenzene; 7.1.24 propylbenzene; 7.1.25 4- ethyltoluene; 7.1.26 trimethylbenzene; 7.1.27 butylbenzene; 7.1.28 tetramethylbenzene; 7.1.29 methyl tert-butyl ether; 7.1.30 ethanol.
  • Warning: these compounds are all flammable or toxic compounds, and if ingested, inhaled or absorbed through the skin, they will cause harm or death to the human body.
• 7.2 System verification sample: a quantitative mixture of pure hydrocarbon compounds is used to check the reliability of the analysis system, optimize the operating temperature and valve switching time of the system, and ensure the accuracy of analysis results. The composition of a typical system verification sample is shown in Table 3 (total saturated hydrocarbons 48.5%, total olefins 12.5%, total aromatics 39.0%).
• 7.3 Quality control check sample: used for routine checking of the reliability of the chromatographic system and separation system, and checking the trapping capacity of the olefin trap; it can be prepared from hydrocarbon compounds similar to the test sample; it should be sealed in ampoules and stored at low temperature, and remain unchanged during storage; the system verification sample in Table 3 can be used as a quality control check sample; Table 4 is the composition of a typical system verification sample containing MTBE (saturated hydrocarbons 41.9%, olefins 11.0%, aromatics 38.0%, ethers MTBE 9.0%); Table 5 is the composition of a typical system verification sample containing ethanol (saturated hydrocarbons 41.3%, olefins 11.6%, aromatics 37.3%, alcohol ethanol 10.0%).
• 7.4 Gases:
  • 7.4.1 Compressed air: combustion-supporting gas, purity not less than 99.9%; warning: high-pressure gas, pay attention to safety.
  • 7.4.2 Hydrogen: fuel gas, purity not less than 99.9%; warning: high-pressure gas, extremely flammable.
  • 7.4.3 Both air and hydrogen need to be purified; use molecular sieve and activated carbon purifiers to remove water and hydrocarbon substances from the gases.
  • 7.4.4 Carrier gas: high-purity nitrogen or helium, purified according to the requirements of 7.6.
• 7.5 Sample bottles: use small glass vials with a crimp cap or screw cap and a rubber gasket lined with a polytetrafluoroethylene face in the cap.

5. Instruments and equipment

• 6.1 Gas chromatograph: should at least include an injector, vaporization chamber, column oven, flame ionization detector (FID) and chromatographic workstation; stable control of carrier gas and detector gas flow rates is very important, and a chromatographic system with electronic flow control should be used; FID should meet or exceed the requirements of Table 1; it also requires a chromatographic column, olefin trap, balance column, switching valve and corresponding temperature control devices.
  • Table 1 Performance requirements for flame ionization detector: noise/A 10^-13–10^-12; drift/(A/h) 10^-12; detection limit (n-C6H14)/(g/s) 10^-11–10^-10; linear range 10^5~10^6.
• 6.2 Olefin trap: at a specific temperature, when the aliphatic hydrocarbons separated from the sample by the polar column (a mixed component of saturated hydrocarbons and olefins) pass through, it should completely retain the olefin components in the aliphatic hydrocarbons and allow the saturated hydrocarbon components to pass through; generally the olefin trapping temperature is 120 ℃~135 ℃; after the temperature is raised, all retained olefin components should be completely released, and the general release temperature is 190 ℃~210 ℃; the specific temperature setting can be determined according to the specific conditions of the olefin trap; performance can be verified with a system verification sample or quality control sample; if olefin breakthrough is found, it is advisable to adjust the operating conditions up to replacing the olefin trap.
• 6.3 Balance column: has no retention or adsorption for hydrocarbon group components, and only serves to balance pressure, so as to ensure a stable baseline during valve switching.
• 6.4 Switching valve: the analysis system should include 2 two-position six-port valves; valve switching can be manual or automatic; to ensure accurate valve switching time, automatic switching valves should be used.
• 6.5 Temperature control of analysis system components: the polar separation column, olefin trap and switching valve should each have an independent temperature control system; all parts in contact with the sample should be maintained at a certain temperature to prevent sample condensation; Table 2 lists typical control temperature ranges; some components require isothermal operation, while others require repeatable programmed temperature operation; the temperatures in Table 2 are only typical operating temperature ranges and can be appropriately adjusted in specific use.
  • Table 2 Temperature control of system components: polar separation column 100–120 ℃, isothermal; olefin trap 115–210 ℃, programmed temperature 30 ℃/min–50 ℃/min; switching valve 100–160 ℃, isothermal; sample line 100~160 ℃, isothermal.
• 6.6 Valve switching drive system: if the valve switching adopts a pneumatic drive system, the air pressure supplied to the pneumatic system should meet the drive requirements to achieve rapid valve switching.
• 6.7 Carrier gas purification device: in addition to the conventional molecular sieve, activated carbon and other purifiers used in gas chromatography to remove water and hydrocarbon impurities from the carrier gas, a dedicated oxygen removal purifier should be installed to ensure that the oxygen volume fraction in the carrier gas is below 1 μL/L.
• 6.8 Chromatographic column: polar separation column; any chromatographic column that satisfies complete separation of benzene from n-dodecane or 1- undecene in aliphatic hydrocarbons, and complete separation of benzene from toluene, and leaves suitable valve switching time may be used; it is required that the retention time ratio of benzene to 1- undecene (t benzene/t1- undecene) is greater than 1.5 and the resolution Rs is greater than 2.0, and the retention time ratio of toluene to benzene (t toluene/t benzene) is greater than 1.25 and the resolution Rs is greater than 1.25; typical chromatographic column preparation: BCEF as stationary liquid, coating amount (mass fraction) 25%, acid-washed 6201 or Chromosorb P (AW) 200 μm~300 μm as support, column tube material is passivated stainless steel tube or inner-wall deactivated stainless steel tube, length 5 m, inner diameter 2 mm; Figure 3 is a performance verification chromatogram of a polar separation column (Note: in the figure, the retention time ratio of benzene to 1- undecene is 1.59, and the retention time ratio of toluene to benzene is 1.31).
• 6.9 Recording and data processing unit: it is preferable to use a chromatographic workstation with the following functions: can display the acquired chromatogram; display the peak area and area percentage data of chromatographic peaks; calculation and use of correction factors; has the function of handling noise and ghost peaks; can perform necessary manual integration processing; the measurement results are calculated by the corrected area normalization method through chromatographic peak areas or area fractions, the corresponding relative mass correction factors, and relevant parameters.

6. Recommended operating conditions

• Table 6 Typical chromatographic operating conditions:
  • Vaporization chamber temperature/℃: 250
  • Polar separation column temperature control/℃: 102~110
  • Olefin trap temperature/℃: 120~135
  • Olefin release temperature/℃: 190~210
  • Carrier gas flow rate/(mL/min): 25~45
  • Detector gas flow rate/(mL/min): air 300–500; hydrogen 40–70
  • Injection volume/μL: 0.1
  • Valve switching drive pressure/kPa: 200~300
• Table 7 Typical retention time ranges of each hydrocarbon group component (through a BCEF column of column length 5 m and an olefin trap under the conditions of Table 6):
  • Saturated hydrocarbons: 0.6~3.0 min
  • Benzene: 3.0~4.5 min
  • C7+ aromatics: 5.0~9.0 min
  • Olefins: 9.0~13.0 min

7. Sampling and sample preparation

• 10.1 Sample collection and preparation: sample according to the GB/T 4756 method. If the sample is not analyzed immediately after sampling, it should be sealed and stored in a refrigerator to prevent volatilization of light components in the sample.
• 5.5 A small amount of dissolved water in the sample does not interfere with the determination; if free water is present, it can be removed by filtration with anhydrous sodium sulfate or filter paper.
• 10.3 Take about 0.1 μL of a representative test sample and inject it into a ready gas chromatographic system.

8. Analysis steps

• 10.2 Preparation of the analysis system: after turning on the instrument, check whether the parameter settings of the analysis system are accurate. To purify the analysis system, before analyzing samples, the instrument should be run empty once according to the sample analysis steps to drive out residual impurities in the chromatographic column and olefin trap.
• 10.3 Take about 0.1 μL of a representative test sample and inject it into a ready gas chromatographic system. The sample flow path is as follows: a) passes through the polar separation column; on the polar separation column, aliphatic hydrocarbon and aromatic hydrocarbon components are completely separated. b) The mixture components of saturated hydrocarbons and olefins separated from the polar separation column enter the olefin trap; in the olefin trap, the olefin components are selectively retained while saturated hydrocarbons pass through the olefin trap and enter the FID detection (see Figure 4). Before benzene elutes from the polar separation column, switch the six-way valve 3B so that the olefin trap is disconnected from the carrier gas flow path and sealed; at this time, the benzene separated from the polar column enters the FID detection through the balance column [see Figure 5a)]. c) After benzene has completely eluted, switch another six-way valve 3A so that C7+ (containing C7) and above C7+ aromatics are backflushed out of the polar column and enter the FID detection [see Figure 5b)]. d) While the C7+ aromatics are being backflushed, begin to raise the temperature of the olefin trap. After the C7+ aromatic components are completely eluted, switch the six-way valve 3B again so that the olefin trap re-enters the carrier gas flow path; at this time, olefins are desorbed from the olefin trap and enter the FID detection [see Figure 5c)]. The obtained chromatogram is processed by the chromatographic workstation and corresponding analysis software to calculate the mass fraction or volume fraction of each component. For a typical gasoline analysis chromatogram, see Figure 6. For solvent oil samples, if olefins do not need to be analyzed, only the steps a) and c) are performed, and the typical chromatogram obtained is shown in Figure 7.
• 8. Establishment and preparation of the instrument system:
  • 8.1 The integration of the gas chromatograph and separation system is shown in Figure 2. If a commercial system is used, contact the manufacturer for installation, positioning, and system optimization.
  • 8.2 Impurities in the carrier gas will adversely affect the performance of the chromatographic column and olefin trap. A reliable carrier gas purification system (6.7) should be installed to ensure normal operation of the system.
  • 8.3 The separation effect of the polar column on aliphatic hydrocarbons and aromatic hydrocarbons and the elution times of benzene and C7+ aromatic components can be checked by actual samples, system verification samples, or quality control check samples to determine the valve switching time. Adjust the temperature of the olefin trap through system verification samples or actual samples until the trapping requirements for olefins and ether compounds are met. Typical chromatographic operating conditions are shown in Table 6.
• 9. System verification and standardization:
  • 9.1 Instrument system reliability check: use a system verification sample (7.2) as the test sample, conduct two tests, one passing through the olefin trap and one not passing through the olefin trap, and compare the peak area values of the C7+ aromatics measured in the two tests. If the system is normal, the difference between the measured values of the C7+ aromatics in the two tests should not exceed the repeatability requirement of the method; otherwise, check whether there are problems with the piping connections of the instrument system, the six-way valve, and the purity of the carrier gas.
  • 9.2 Performance check of the olefin trap: system verification samples, quality control check samples, or actual samples with high olefin content may be used to check the performance of the olefin trap. Under the determined test conditions, the olefin trap should pass all saturated hydrocarbon components and trap all olefin components, see Figure 4. The deviation of the measurement results should not exceed the reproducibility requirement for the content level of each component in the system verification or quality control check sample. Otherwise, the analysis conditions should be adjusted to meet the above requirements, and if necessary, the olefin trap should be replaced.
  • 9.3 Determination of retention time ranges: the retention time ranges of saturated hydrocarbons, benzene, C7+ aromatics, and olefin components can be determined by system verification samples or actual gasoline samples. Table 7 gives the retention time ranges of each hydrocarbon group component through a BCEF column of column length 5 m and an olefin trap under the conditions of Table 6. Figure 4 is the chromatogram of the system verification sample of Table 4.
• 11. Quality control: to confirm the reliability of the analysis system, a system verification sample (7.2) or quality control check sample (7.3) should be analyzed every two weeks. The difference between the measurement results and the reference values of the system verification or quality control sample should be less than the reproducibility requirement; otherwise, the source of error should be determined and necessary corrections made. Actual samples may be used as quality control samples, but the development of quality control samples refers to GB/T 15000.

9. Qualitative and quantitative determination and calculation formulas

• 12.1 Calculation of each hydrocarbon group composition and benzene content in the test sample
  • 12.1.1 Check the integration status of the chromatogram by the integrator or chromatographic workstation to determine whether all chromatographic peaks have been reasonably integrated. If unreasonable, the manual integration function of the workstation may be used to correct the baseline and then re-integrate. Note: Because the benzene content in gasoline is relatively low, unreasonable baseline cutting and integration will have a large impact on the analysis results.
  • 12.1.2 Relative mass correction factors: the values and calculation of the relative mass correction factors of each hydrocarbon group component are given in Appendix B. For gasoline products that meet the distillation range requirements of GB/T 17930, based on the distribution of components with different carbon numbers in each hydrocarbon group and the response on the hydrogen flame ionization detector, the calculated values of the relative mass correction factors of each hydrocarbon group component relative to C7+ aromatics are shown in Table 8.
    • Table 8 Average mass correction factors of each hydrocarbon group component: saturated hydrocarbons 1.0774; olefins 1.0560; C7+ aromatics 1.0000; benzene 0.9798.
    • For other distillate samples, the mass correction factor relative to C7+ aromatics may also be obtained experimentally using standard samples according to formula (1): fi = (mi·PA)/(mA·Pi) ………………(1) Where: fi—— relative mass correction factor; mA—— mass fraction of C7+ aromatics in the standard sample, %; PA—— peak area fraction of C7+ aromatics in the standard sample determined by chromatography; mi—— mass fraction of saturated hydrocarbons, olefins, or benzene in the standard sample; Pi—— peak area fraction of saturated hydrocarbons, olefins, or benzene in the standard sample determined by chromatography.
  • 12.1.3 The mass fractions of saturated hydrocarbons, olefins, C7+ aromatics, and benzene in the test sample are calculated according to formula (2): Mi = (Pi·fi / ∑Pi·fi) × 100 ………………(2) Where: Mi—— mass fraction of a certain component i in the test sample, %; fi——i relative mass correction factor of the component; Pi——i peak area fraction of the component determined by chromatography.
  • 12.1.4 The volume fractions of saturated hydrocarbons, olefins, C7+ aromatics, and benzene in the test sample are calculated according to formula (3): Vi = (Pi·fi/di / ∑Pi·fi/di) × 100 ………………(3) Where: Vi—— volume fraction of a certain component i in the test sample, %; fi——i relative mass correction factor of the component; Pi——i peak area fraction of the component determined by chromatography; di—— weighted relative density of saturated hydrocarbons, olefins, and C7+ aromatics and relative density of benzene, see 12.1.5.
  • 12.1.5 The values and calculation of the weighted relative density of each hydrocarbon group component are given in Appendix C. For gasoline products that meet the distillation range requirements of GB/T 17930, the values in Table 9 may be used for the weighted relative density of each hydrocarbon group component. For gasoline with a special distillation fraction, the calculation method is given in Appendix C. If the weighted relative density does not use the values in Table 9, the values used shall be noted in the report under "other circumstances".
    • Table 9 Weighted relative density of each hydrocarbon group component at 20 ℃ (unit: grams per milliliter): saturated hydrocarbons 0.6776; olefins 0.6745; C7+ aromatics 0.8695; benzene 0.8789.
  • 12.1.6 When the gasoline contains ether or alcohol compounds, NB/SH/T 0663 shall be used to first determine the content of each oxygen-containing compound, and finally the content of each hydrocarbon group component shall be calculated according to the method in Appendix A.
• 12.2 Reporting of results: report the volume fraction (or mass fraction) of saturated hydrocarbons, olefins, and aromatics in the sample, accurate to 0.1%; the aromatic content is the sum of C7+ aromatic content and benzene content. Report the volume fraction (or mass fraction) of benzene, accurate to 0.01%. Other circumstances.
• Appendix A (normative) Correction of results when oxygen-containing compounds are present in gasoline samples:
  • A.1 Overview: Oxygen-containing compounds such as ethers or alcohols are often added to finished gasoline to improve the octane number and emission status of gasoline. When the gasoline contains ether or alcohol compounds, when analyzed by this method, the ether compounds in the gasoline will peak together with the olefin components, while the alcohol compounds will peak together with the C7+ aromatic components. Therefore, when measuring the hydrocarbon components in gasoline, the response of the oxygen-containing compounds in the gasoline is deducted from the corresponding hydrocarbon components, and after correction the true content of the hydrocarbon group composition in the gasoline is obtained. According to the requirements of GB 17930, the content of oxygen-containing compounds in gasoline is determined by the methods of NB/SH/T 0663. Based on the measured mass fraction of each oxygen-containing compound and the results of the apparent peak areas of each hydrocarbon component measured during the test procedure of this method, the mass fraction or volume fraction of each gasoline hydrocarbon group component is obtained according to A.2~A.5.
  • A.2 Correction of chromatographic peak area fractions:
    • A.2.1 When the sample contains ether compounds, correct the olefin peak area fraction according to formula (A.1): A'OLE = AOLE - ∑(Ci/fi) ………………(A.1) Where: A'OLE—— the area fraction corresponding to the chromatographic peak of the olefin component in the sample after correction, %; AOLE—— the apparent olefin chromatographic peak area fraction measured by chromatography, %; Ci—— the mass fraction of the ith ether compound, %; fi—— the relative mass correction factor corresponding to that ether compound, see Table A.1.
      • Table A.1 Relative correction factors of typical oxygen-containing compounds in gasoline: MTBE 1.30; ETBE 1.29; TAME 1.27; ethanol 2.51; methanol 3.75; isopropanol 1.85; tert-butanol 1.35.
    • A.2.2 When the sample contains alcohol compounds, correct the C7+ aromatic peak area fraction according to formula (A.2): A'ARO = AARO - ∑(Cj/fj) ………………(A.2) Where: A'ARO—— the area fraction corresponding to the chromatographic peak of the C7+ aromatic component in the sample after correction, %; AARO—— the apparent C7+ aromatic chromatographic peak area fraction measured by chromatography, %; Cj—— the mass fraction of the jth alcohol compound, %; fj—— the relative mass correction factor corresponding to that alcohol compound, see Table A.1.
    • A.2.3 The correction factors of common oxygen-containing compounds in gasoline on a hydrogen flame ionization detector are determined experimentally using a reference substance. The measured relative correction factors of typical substances relative to C7+ aromatics are shown in Table A.1.
  • A.3 Calculation of the normalized mass fraction and volume fraction of each hydrocarbon group component: after correcting the peak area fractions of olefins and C7+ aromatics, the peak area fractions of the hydrocarbon components are re-normalized based on the measured area fractions of saturated hydrocarbons and benzene, to obtain the normalized area fraction Pi of each hydrocarbon component, and the normalized mass fraction mi and volume fraction Vi of each hydrocarbon component are calculated according to formula (A.3) and formula (A.4). mi = (Pi·fi / ∑Pi·fi) × 100% ………………(A.3) Vi = (Pi·fi/di / ∑Pi·fi/di) × 100% ………………(A.4) Where: mi—— the mass fraction of hydrocarbon group component i in the hydrocarbon components, %; Vi—— the volume fraction of hydrocarbon group component i in the hydrocarbon components, %; fi——i the relative mass correction factor of the hydrocarbon group component; Pi—— the peak area fraction of component i determined by chromatography after normalization, %; di—— the weighted relative density of saturated hydrocarbons, olefins, and C7+ aromatics, and the relative density of benzene.
  • A.4 Calculation of the mass fraction of each hydrocarbon group component in gasoline: calculate the mass fraction of each hydrocarbon group component in the sample according to formula (A.5). m'i = mi × (100 - ∑COXY)/100% ………………(A.5) Where: m'i—— the mass fraction of hydrocarbon group component i in gasoline, %; mi—— the mass fraction of hydrocarbon group component i in the hydrocarbon components, %; ∑COXY—— the sum of the mass fractions of all oxygen-containing compounds in the sample, %.
  • A.5 Calculation of the volume fraction of each hydrocarbon group component in gasoline:
    • A.5.1 Since the density of the hydrocarbon components in gasoline differs from the density of the oxygen-containing compounds, the influence of the density difference on the volume fraction must be considered when converting volume fractions.
    • A.5.2 Calculate the relative weighted density of the hydrocarbons in the sample dHC according to formula (A.6): dHC = ∑mi·di/100% ………………(A.6) Where: di—— the weighted relative density corresponding to the ith hydrocarbon group component (including saturated hydrocarbons, benzene, C7+ aromatics, olefins); mi—— the mass fraction of each hydrocarbon group component i in the hydrocarbon components, %.
    • A.5.3 The volume fraction VOXY occupied by the oxygen-containing compounds in the sample is calculated according to formula (A.7): VOXY = ∑(Ci/di)/[∑(Ci/di) + (100 - ∑Ci)/dHC] ………………(A.7) Where: Ci—— the mass fraction of the ith oxygen-containing compound in the sample, %; di—— the relative density of the ith oxygen-containing compound, values are given in Table A.2; dHC—— the weighted relative density of the hydrocarbons in gasoline.
      • Table A.2 Relative density of common oxygen-containing compounds in gasoline (20 ℃): MTBE 0.7459; ETBE 0.7440; TAME 0.7710; ethanol 0.7967; methanol 0.7963; isopropanol 0.7851; tert-butanol 0.7753.
    • A.5.4 The volume fraction occupied by each hydrocarbon group component in the sample is calculated according to formula (A.8): V'i = Vi × (100 - VOXY)/100% ………………(A.8) Where: V'i—— the volume fraction of hydrocarbon group component i in the sample, %; Vi—— the volume fraction of hydrocarbon group component i in the hydrocarbon components, %; VOXY—— the volume fraction occupied by the oxygen-containing compounds in the sample, %.
• Appendix B (informative) Calculation of the relative mass correction factor of each hydrocarbon group component:
  • B.1 Calculation of the mass response factor of hydrocarbon compounds relative to methane: according to GB/T 28768, calculate the mass response factor of components with different carbon numbers in each hydrocarbon group relative to methane on FID according to formula (B.1), see Table B.1. fM = [(12.011×Cn) + (1.008×Hn)] × 0.7487 / (12.011×Cn) ………………(B.1) Where: fM—— the mass response factor of a certain hydrocarbon compound relative to methane; Cn—— the number of carbon atoms in a certain hydrocarbon compound; Hn—— the number of hydrogen atoms in a certain hydrocarbon compound; 12.011—— the relative atomic mass of carbon atoms; 1.008—— the relative atomic mass of hydrogen atoms; 0.7487—— the correction coefficient relative to methane.
    • Table B.1 Mass response factors of components with different carbon numbers in each hydrocarbon group relative to methane on FID (number of carbon atoms 4~11+; paraffins P, naphthenes N, olefins O, aromatics A; specific values are given in Table B.1 of the original text).
  • B.2 Determination of the composition of components with different carbon numbers in each hydrocarbon group: use SH/T 0714 or GB/T 28768 to determine the components with different carbon numbers in the hydrocarbon groups, and report the data according to Table B.2.
    • Table B.2 Mass fraction of components with different carbon numbers (%) (number of carbon atoms 4~11+; paraffins P, naphthenes N, olefins O, aromatics A; specific symbols are given in Table B.2 of the original text).
  • B.3 Calculation of the mass response factor of each hydrocarbon group component relative to methane:
    • B.3.1 The mass response factor of paraffins relative to methane is calculated according to formula (B.2): fMP = ∑(Pi·fMPi)/PT ………………(B.2)
    • B.3.2 The mass response factor of naphthenes relative to methane is calculated according to formula (B.3): fMN = ∑(Ni·fMNi)/NT ………………(B.3)
    • B.3.3 The mass response factor of total saturated hydrocarbons relative to methane is calculated according to formula (B.4): fMS = (PT·fMP + NT·fMN)/ST ………………(B.4)
    • B.3.4 The mass response factor of total olefins relative to methane is calculated according to formula (B.5): fMO = ∑(Oi·fMOi)/OT ………………(B.5)
    • B.3.5 C7+ The mass response factor of aromatics relative to methane is calculated according to formula (B.6): fMA = ∑(Ai·fMAi)/AT ………………(B.6)
  • B.4 Calculation of the mass correction factor of each hydrocarbon group component relative to C7+ aromatics: The mass correction factor of each hydrocarbon group component relative to C7+ aromatics is calculated according to formula (B.7): fi = fMi/fMA ………………(B.7)
• Appendix C (informative) Calculation of the weighted relative density of each hydrocarbon group component:
  • C.1 Relative density of different carbon number components in each hydrocarbon group: The relative densities cited for different carbon number components in each hydrocarbon group are shown in Table C.1.
    • Table C.1 Relative density of different carbon number components (20 ℃) (carbon atom number 4~11+; paraffins P, naphthenes N, olefins O, aromatics A; specific values are shown in Table C.1 of the original text).
  • C.2 Determination of the composition of different carbon number components in each hydrocarbon group: The composition of different carbon number components in the hydrocarbon group determined by SH/T 0714 or GB/T 28768 is shown in Table C.2.
    • Table C.2 Mass fraction of different carbon number components (%) (carbon atom number 4~11+; paraffins P, naphthenes N, olefins O, aromatics A; specific symbols are shown in Table C.2 of the original text).
  • C.3 Calculation of the weighted relative density of each hydrocarbon group component:
    • C.3.1 The weighted relative density of paraffins is calculated according to formula (C.1): dP = ∑(Pi·dPi)/PT ………………(C.1)
    • C.3.2 The weighted relative density of naphthenes is calculated according to formula (C.2): dN = ∑(Ni·dNi)/NT ………………(C.2)
    • C.3.3 The weighted relative density of saturated hydrocarbons is calculated according to formula (C.3): dS = (PT·dP + NT·dN)/ST ………………(C.3)
    • C.3.4 The weighted relative density of olefins is calculated according to formula (C.4): dO = ∑(Oi·dOi)/OT ………………(C.4)
    • C.3.5 C7+ The weighted relative density of aromatics is calculated according to formula (C.5): dA = ∑(Ai·dAi)/AT ………………(C.5)

10. Precision

• 13.1 Overview: The precision of this document was obtained through collaborative testing by 10 laboratories on 24 samples. The precision of this document is determined according to GB/T 6683.1 through inter-laboratory statistical analysis results. The reliability of test results is judged according to 13.2~13.4 (95% confidence level).
• 13.2 Repeatability (r): The difference between 2 test results obtained by the same operator, in the same laboratory, using the same instrument, according to the same test method, on the same test sample for continuous determination shall not exceed the values listed in Table 10 or Table 11.
• 13.3 Reproducibility (R): The difference between 2 single, independent results obtained by different operators, in different laboratories, using different instruments, according to the same test method, on the same test sample for separate determination shall not exceed the values listed in Table 10 or Table 11.
• 13.4 Precision for solvent oil: The precision of the aromatics method in solvent oil is estimated according to Table 10.
• Table 10 Precision:
  • Saturated hydrocarbons: Repeatability/% 0.8; Reproducibility/% 1.8; Volume fraction range/% 28~78.
  • Olefins: Repeatability/% 0.12X^0.54; Reproducibility/% 0.30X^0.58; Volume fraction range/% 0.5~70.
  • Aromatics: Repeatability/% 0.16X^0.48; Reproducibility/% 0.33X^0.54; Volume fraction range/% 1~80.
  • Benzene: Repeatability/% 0.05X^0.64; Reproducibility/% 0.12X^0.72; Volume fraction range/% 0.2~10.
  • C7+ Aromatics: Repeatability/% 0.14X^0.46; Reproducibility/% 0.32X^0.50; Volume fraction range/% 1~70.
  • Note: X is the average volume fraction of the component.
• Table 11 Precision at typical content levels:
  • Olefins: At 5%, repeatability 0.3%, reproducibility 0.8%; at 10%, 0.4%, 1.1%; at 15%, 0.5%, 1.4%; at 20%, 0.6%, 1.7%; at 25%, 0.7%, 1.9%; at 30%, 0.8%, 2.2%; at 35%, 0.8%, 2.4%; at 40%, 0.9%, 2.5%; at 45%, 0.9%, 2.7%; at 50%, 1%, 2.9%.
  • Aromatics: At 5%, repeatability 0.3%, reproducibility 0.8%; at 10%, 0.5%, 1.1%; at 15%, 0.6%, 1.4%; at 20%, 0.7%, 1.7%; at 25%, 0.8%, 1.9%; at 30%, 0.8%, 2.1%; at 35%, 0.9%, 2.3%; at 40%, 0.9%, 2.4%; at 45%, 1.0%, 2.6%.
  • Benzene: At 0.5%, repeatability 0.03%, reproducibility 0.07%; at 1.0%, 0.05%, 0.12%; at 1.5%, 0.06%, 0.16%; at 2.0%, 0.08%, 0.20%; at 2.5%, 0.09%, 0.23%.

11. Report

• 12.2 Result report: Report the volume fraction (or mass fraction) of saturated hydrocarbons, olefins, and aromatics in the test sample, accurate to 0.1%, and the aromatics content is the sum of C7+ aromatics content and benzene content. Report the volume fraction (or mass fraction) of benzene, accurate to 0.01%. Other circumstances.
• 12.1.5 If the weighted relative density does not use the values in Table 9, it should be stated in the report "