NB/SH/T 0230-2019 Determination of liquefied petroleum gas composition by gas chromatography

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Card type: Test method

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

• Method number: NB/SH/T 0230—2019
• Chinese full name: Determination of liquefied petroleum gas composition by gas chromatography
• English name: Determination of composition in liquefied petroleum gases by gas chromatography
• Replacement relationship: replaces SH/T 0230—1992 "Determination of liquefied petroleum gas composition (chromatographic method)"
• Publication/implementation: published on 2019-06-04, implemented on 2019-10-01
• Issuing body: National Energy Administration
• Drafting rules: drafted according to the rules given in GB/T 1.1—2009
• Custodianship: Subcommittee on Petroleum Fuels and Lubricants of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280/SC1)
• Proposed by: China Petrochemical Corporation
• Responsible drafting organization: Research Institute of Petroleum Processing, Sinopec Corp.
• Participating drafting organizations: Guangdong Huizhou Petroleum Product Quality Supervision and Inspection Center, Shenzhen Institute of Metrology and Quality Inspection, Shandong Chambroad Petrochemicals Co., Ltd., Petrochemical Research Institute of PetroChina Company Limited, Shandong Baisen Chemical Technology Testing Co., Ltd., Guangdong Maoming Quality Supervision and Inspection Institute, Sinochem Quanzhou Petrochemical Co., Ltd.
• Main drafters: Wang Yamin, Yang Tingting, Wen Huan, Zhao Yan, Liu Jianli, Liu Jinsheng, Wang Chunyan, Wang Hao, Huang Shuiwang, Chen Shitai, Xu Dongyu, Zhao Chuanhua
• Main changes compared with SH/T 0230—1992:
  • Expanded scope of application (originally only applicable to pure hydrocarbon liquefied petroleum gas containing C₃~C₄; now adds determination of hydrocarbon and oxygenate composition of liquefied petroleum gas containing oxygenates such as dimethyl ether)
  • Changed sample injection mode (uses a commercial liquid valve or flash evaporator instead of the original water-bath vaporization injection mode)
  • Uses a single-column, single-valve, single-detector system configured with a Al₂O₃ capillary chromatographic column and a hydrogen flame ionization detector (system 1) to replace the original analysis system
  • Adds an oxygenate-containing liquefied petroleum gas composition analysis system (system 2, dual-valve, dual-column, dual-detector, completing in one injection the full analysis of oxygenates such as dimethyl ether, methyl tert-butyl ether, methanol, acetone and hydrocarbon components C₃~C₄)
  • Revised the calibration factors used for quantification in the method and re-established the method precision data
  • Adds Annex A (informative annex), providing a reference chromatogram for qualitative identification of unknown oxygenates in complex liquefied petroleum gas samples

2. Scope of application and non-applicability

• This standard specifies a test method for determining the composition of liquefied petroleum gas by gas chromatography.
• Applicable to the determination of hydrocarbon composition in finished liquefied petroleum gas.
• It can also be used for the determination of hydrocarbon and oxygenate components (such as dimethyl ether, methyl tert-butyl ether, acetone and methanol, etc.) in liquefied petroleum gas containing oxygenates.
• Determination range (volume fraction):
  • Hydrocarbon components: 0.01%~100%
  • Dimethyl ether: 1%~40%
  • Methyl tert-butyl ether: 0.01%~1%
  • Methanol: 0.01%~1%
  • Acetone: 0.01%~1%
• Samples outside the determination range: the detection range may be adjusted by changing the analysis conditions according to analysis needs, but this standard does not provide precision data for the corresponding determination range.
• Two chromatographic analysis systems:
  • System 1: suitable for determining hydrocarbon components in pure hydrocarbon liquefied petroleum gas, mainly C₃~C₄ hydrocarbons.
  • System 2: in addition to satisfying the sample determination of system 1, it can also be used to determine the hydrocarbon and oxygenate composition in liquefied petroleum gas containing oxygenates (such as dimethyl ether), with the main determined components being C₃~C₄ hydrocarbons and oxygenates (such as dimethyl ether, methyl tert-butyl ether (MTBE), acetone, methanol, etc.).
• Not applicable: the source text does not explicitly list a "not applicable" clause.

3. Method principle

• 3.1 For pure hydrocarbon liquefied petroleum gas samples, inject in liquid form through a liquid valve, or inject after uniform vaporization through a flash evaporator, and analyze the test sample using a single-column, single-valve, single-detector system (system 1). Based on the chromatographic peak area data, use a liquefied petroleum gas calibration sample and calculate the volume fraction of each component by the calibrated normalization method.
• 3.2 For liquefied petroleum gas samples containing oxygenates, inject in liquid form through a liquid valve, or inject after uniform vaporization through a flash evaporator, and use a dual-column, dual-valve, dual-detector system (system 2) to complete the full analysis of oxygenates and hydrocarbon composition in the sample in one injection. Based on the chromatographic peak area data, use a liquefied petroleum gas calibration sample containing oxygenates, calculate the volume fraction of each oxygenate using the calibration curve, and calculate the volume fraction of hydrocarbon components using the differential calibrated normalization method.

4. Reagents and materials (purity / preparation)

• 6.1 Liquefied petroleum gas calibration sample: an accurate calibration sample is key to the success of quantitative analysis. It is a liquid mixed sample, stored in a pressurized steel cylinder with an internal dip tube or other equipment capable of transferring the liquid sample out. Preparation shall comply with the requirements of GB/T 5274/ISO 6142. After the liquid sample is prepared, a propellant gas (helium is recommended) needs to be charged into the steel cylinder to ensure the stability and representativeness of the liquid sample. The propellant gas charging pressure shall reach at least 1 MPa or above.
  • 6.1.1 The recommended liquefied petroleum gas calibration sample contains the following hydrocarbon components: ethane, propane, propylene, isobutane, n-butane, trans-butene, n-butene, isobutene, cis-butene, 1,3- butadiene, 1- pentene.
  • 6.1.2 The recommended oxygenate-containing calibration sample may include the following oxygenate components: dimethyl ether, methyl tert-butyl ether, methanol, acetone. It may also be prepared as needed.
  • 6.1.3 (the original numbering is missing, requires confirmation against the source standard (source-text extraction)) The nominal values of each component in the calibration sample are expressed as volume fraction. The nominal values of each component in the calibration sample should be as close as possible to the actual sample content.
  • 6.1.4 The pressure regulator equipped on the pressurized steel cylinder should be suitable for transferring liquid samples. When preparing a mixed liquefied petroleum gas calibration sample containing oxygenates, the inner wall of the steel cylinder, the pressure regulator and additional accessories need to be inertized.
• 6.2 Carrier gas: helium, purity of 99.999% or above. Sufficient pressure shall be provided to ensure a stable carrier gas flow rate for the system.
• 6.3 Fuel gas: hydrogen, purity of 99.999% or above.
• 6.4 Combustion-supporting gas: compressed air.
• 6.5 Makeup gas: nitrogen, purity of 99.999% or above.
• Note: It is recommended that the carrier gas, hydrogen, air and nitrogen be further purified. Molecular sieves or other suitable reagents may be used to remove water, oxygen and hydrocarbon impurities from each gas to protect the service life of the chromatographic column.
• 6.6 Quality control check sample: the calibration sample described in 6.1 and actual samples that can ensure stability.

5. Instruments and equipment

• 5.1 Gas chromatograph: any gas chromatograph with quality assurance and a configuration meeting the analysis requirements may be used. Figure 1 and Figure 2 are the flows of the two chromatographic systems recommended by the method (system 1 and system 2).
• 5.2 Chromatographic column
  • 5.2.1 System 1 chromatographic column: any chromatographic column capable of completely separating all hydrocarbon components from C₃~C₄ may be used. A Al₂O₃ chromatographic column with added strongly polar deactivating salt, such as one with a column length of 30 m, an inner diameter of 0.53 mm, a liquid film thickness of 15 μm, model GS-ALUMINA, or a M type Al₂O₃ capillary chromatographic column, can meet the determination requirements of the method.
  • 5.2.2 System 2 chromatographic columns may be configured as follows:
    • a) Chromatographic column 1: same as system 1
    • b) Chromatographic column 2: any strongly polar chromatographic column capable of meeting the determination requirements of the method may be used. For example, a capillary chromatographic column with unique selectivity for multiple oxides, length 10 m, inner diameter 0.53 mm, liquid film thickness 10 μm, model Lowox
    • c) Guard column: a particulate trap for chromatographic column 2, with specifications of a specially treated inner wall, column length 2.5 m, inner diameter 0.53 mm capillary. Used to prevent particles from plugging the valve rotor or leaving scratches when particles deposited on the chromatographic column wall fall off
    • d) Connecting column: deactivated quartz column tube, length 0.5 m~0.8 m, inner diameter 0.53 mm
  • 5.2.3 Chromatographic column performance: the retention and separation capability of the selected chromatographic column can provide the separation effects shown in Figure 3 and Figure 4. The column bleed of all chromatographic columns shall be low enough to ensure that when the column temperature rises to 200 ℃, the column bleed does not affect the detector response.
• 5.3 Detector: a hydrogen flame ionization detector (FID) equipped with an electronic flow controller is recommended; other detectors that can meet the actual sample minimum detection limit and linear range may also be used.
• 5.4 Data acquisition system: any commercial chromatographic workstation capable of acquiring single (dual) FID signals, recording chromatograms, performing qualitative identification by retention time and reporting chromatographic peak areas may be used.
• 5.5 Sample injection equipment
  • 5.5.1 Liquid valve: has the function of directly introducing a liquid liquefied petroleum gas sample into the injection port of the gas chromatograph. The liquid valve design shall withstand a liquid injection pressure of at least 1380 kPa. The liquid valve shall include necessary components such as a quantitative loop, a four-way valve, and a flow control unit that ensures the sample enters the chromatograph in liquid form. A filter shall be installed between the inlet of the quantitative loop and the outlet of the steel cylinder to remove particulate matter from the sample; the outlet line of the quantitative loop is directly connected to the injection port of the chromatograph through an injection needle. When continuously testing the same sample, the liquid valve injection is required to meet the index requirement that the relative standard deviation of the peak area of each component is less than 3%.
  • 5.5.2 Flash evaporator: has the function of instantly and completely converting a small amount of liquid sample from liquid to gas. The valve system design of the flash evaporator shall at least meet the requirement of withstanding a liquid injection pressure of 1380 kPa at an operating temperature of 100 ℃. The flash evaporator shall include necessary components such as a temperature control unit and a fixed-volume vaporization chamber that instantly and uniformly vaporize all components, interface accessories connected to the gas injection valve of the chromatograph, and a filter for removing particulate matter from the sample. When continuously testing the same sample, the flash evaporator injection is required to meet the index requirement that the relative standard deviation of the peak area of each component is less than 4%.

6. Recommended operating conditions

• Table 1 Typical chromatographic conditions:
  • Chromatographic column:
    • System 1: chromatographic column 1 Al₂O₃, column length 30 m, internal diameter 0.53 mm, liquid film thickness 15 μm
    • System 2: chromatographic column 1 Al₂O₃, column length 30 m, internal diameter 0.53 mm, liquid film thickness 15 μm; chromatographic column 2 Lowox, column length 10 m, internal diameter 0.53 mm, liquid film thickness 10 μm
  • Carrier gas: helium (purity 99.999% or above)
  • Quantitative loop: 0.5 mL~1.0 mL (recommended 0.5 mL); 0.5 μL (for chromatographs equipped with a liquid valve)
  • Valve oven temperature: 150 ℃
  • Inlet temperature: 200 ℃
  • Split ratio: (10:1)~(50:1), recommended 50:1
  • Chromatographic column control mode: constant flow 4.5 mL/min
  • Single/dual flame ionization detector (FID): temperature 230 ℃; hydrogen flow rate 30 mL/min, air flow rate 350 mL/min, nitrogen flow rate 25 mL/min
  • Column temperature program: initial temperature 90 ℃, hold 1 min, ramp rate 6 ℃/min, final temperature 180 ℃, hold 30 min
  • Valve events:
    • System 1: at 0.01 min valve 1 opens; at 0.5 min valve 1 closes
    • System 2: at 0.01 min valve 1 opens; at 0.5 min valve 1 closes; at 6 min valve 2 opens; at 45 min valve 2 closes
  • Accessory requirements: the quantitative loop, split/splitless inlet, liner, and all lines through which the sample flows must be deactivated; see the bolded part of Figure 2
  • Note: *chromatograph equipped with a gas sampling valve; **chromatograph equipped with a liquid valve; ***determine the opening time of valve 2 according to clause 8.3
• 8.1.1 The chromatographic operating conditions shall be capable of separating all components in the liquefied petroleum gas calibration sample.
• 8.1.2 The chromatographic operating conditions shall ensure that all components of interest in the liquefied petroleum gas sample are eluted and detected.
• 8.2 Aging of new chromatographic columns: both chromatographic column 1 and chromatographic column 2 are porous-layer polar chromatographic columns; column performance is susceptible to ambient temperature and humidity, leading to drift in component retention times and affecting qualitative accuracy. Therefore, before installing a new chromatographic column, it shall be aged as follows:
  • Chromatographic column 1: age at 180 ℃ for 8 h
  • Chromatographic column 2: raise to 300 ℃ at a relatively low ramp rate (e.g., 2 ℃/min), hold for 10 h
• 8.3 Determination of dimethyl ether cut time: for the determination of liquefied petroleum gas samples containing oxygenates, prepare a sample A containing dimethyl ether and toluene, and follow the instrument analysis flow in Figure 2, close valve 1 and open valve 2. Introduce sample A through the split/splitless inlet and simultaneously start the chromatograph, and record the chromatogram. At this time, after toluene and dimethyl ether in sample A pass through chromatographic column 2, they enter detector 2 through the connecting column. Observe the elution time of the toluene component in the chromatogram; the cut time is the toluene peak time minus 0.5 min, i.e., the opening time of valve 2. Figure 5 is an example of dimethyl ether cut time.

7. Sampling and sample preparation

• 7.1 A suitable sampling process and sample handling method are crucial for obtaining representative analytical results and ensuring the normal use of the chromatograph.
• 7.2 Collect liquefied petroleum gas samples in accordance with the requirements of SH/T 0233.
• Note: For liquefied petroleum gas samples containing oxygenates, use sampling cylinders whose inner walls have been deactivated as much as possible.
• 7.3 Before sample analysis, invert the cylinder, open the sample outlet valve, and release a small portion of the sample to remove possible moisture and particulate matter.

8. Analytical procedure

• 10.1 Chromatograph stabilization: after the chromatograph is turned on, the chromatographic column system shall be aged at 180 ℃ for about 4 h or more, then the temperature shall be lowered to the initial analysis temperature, and after stabilizing for about 1 h, sample injection and analysis may be carried out. When the chromatograph is on standby for a long time, it is recommended to control the column oven temperature at 180 ℃.
• 10.2 Sample injection
  • 10.2.1 Liquid valve injection: connect the sample outlet of the test sample cylinder to the sampling port of the liquid valve with fittings and lines that can ensure gas tightness; adjust the flow control unit so that continuous liquid droplets flow out of the vent of the liquid valve, maintain for 20 s~30 s, and start the chromatograph for injection.
  • 10.2.2 Flash evaporator injection: connect the sample outlet of the test sample cylinder to the sampling port of the flash evaporator with fittings and lines that can ensure gas tightness; according to the actual sample distillation distribution, control the vaporization temperature at a certain temperature between 80 ℃~110 ℃ (recommended vaporization temperature 100 ℃); adjust the flow control unit of the flash evaporator, and after ensuring that the sample reaches a uniform vaporization state for about 1 min, start the chromatograph for injection.
• 10.3 Sample analysis: use System 1 or System 2 to test the liquefied petroleum gas sample according to the chromatographic conditions listed in Table 1.
• 10.4 Blank analysis: when a flash evaporator is used as the sample injection device, a blank analysis shall be performed between two sample analyses to ensure that no sample residue or contamination exists in the system. Usually nitrogen or air is used as the blank sample.
• 11 Quality control check: as part of the quality assurance and control process, quality control checks shall be carried out according to the actual quality control regulations of each laboratory. The analysis procedure for the quality control check sample (6.6) is the same as that for sample analysis. The difference between two measurement results of the quality control check sample shall meet the repeatability requirements specified in the method, and the average of the two measurement results shall meet the measurement accuracy requirements of each laboratory's quality control specifications. If the measurement results exceed the range, the source of error shall be identified and corrected.

9. Qualitative and quantitative determination and calculation formulas

• 9.1 Calibration sample preparation: to ensure the quality of calibration samples, all sample preparations shall comply with the requirements of GB/T 5274/ISO 6142. They shall be prepared by manufacturers with production qualifications. When establishing an analytical method, for laboratories that use System 1 to detect only the hydrocarbon composition in liquefied petroleum gas, one bottle of mixed calibration sample shall be prepared to establish the calibration factors for each hydrocarbon component. For laboratories that use System 2 to detect the composition of liquefied petroleum gas containing oxygenates, additionally 3~5 bottles of mixed calibration samples containing oxygenates at different concentrations shall be prepared to establish the calibration curves for each oxygenate component. If the laboratory is already equipped with an online gas blending system, only one bottle of calibration sample containing a high concentration of oxygenates may be prepared.
• 9.2 Hydrocarbon calibration procedure
  • 9.2.1 Hydrocarbon qualitative determination: according to the chromatographic conditions listed in Table 1, complete component qualitative determination based on the retention times of each component of the liquefied petroleum gas calibration sample in the chromatogram.
  • 9.2.2 Hydrocarbon calibration: the volume fraction calibration factor of hydrocarbon components is calculated according to formula (1). Table 2 gives typical volume fraction calibration factors for some hydrocarbon components.
    • Formula (1): Kᵢ = (Aᵢ / Aₛ) × (φₛ / φᵢ) (the original formula source-text extraction is unclear in the source text, requires confirmation against the source standard (source-text extraction))
    • Where: Kᵢ—calibration factor of component i in the calibration sample; φᵢ—nominal volume fraction of component i in the calibration sample, %; Aᵢ—peak area of component i in the calibration sample; φₛ—nominal volume fraction of reference component s in the calibration sample, %; Aₛ—peak area of reference component s in the calibration sample.
    • Note: In practical applications, laboratories that can obtain calibration samples are advised to determine the volume fraction calibration factor of each hydrocarbon compound themselves.
  • Table 2 Typical volume fraction calibration factors for some hydrocarbon components:
    • Ethane: 2.150
    • Propane: 1.396
    • Propylene: 1.427
    • Isobutane: 1.031
    • n-Butane: 1.000 (reference component)
    • trans-2-Butene: 1.024
    • n-Butene: 1.029
    • Isobutene: 1.047
    • cis-2-Butene: 0.997
    • Isopentane: 0.858
    • 1-Pentene: 0.834
• 9.3 Oxygenate calibration procedure
  • 9.3.1 Oxygenate qualitative determination: under the chromatographic conditions of System 2 listed in Table 1, complete component qualitative determination based on the retention times of each component of the oxygenate calibration sample in the chromatogram (see Appendix A).
  • 9.3.2 Oxygenate qualitative standard sample OXY-LPG: to meet the analytical requirements for determining oxygenates in actual samples, the OXY-LPG standard sample described in Appendix A may be used to assist in identifying unknown oxygenates.
  • 9.3.3 Oxygenate quantitative determination: analyze oxygenate calibration samples at different concentration levels according to the chromatographic conditions of System 2 listed in Table 1. Record the peak area of each component, with peak area as the x axis and the content value corresponding to each peak area as the y axis; the calibration curve is expressed according to formula (2), and the slope and intercept of the calibration curve are calculated by the least squares method. Figure 6 is an example of a calibration curve for dimethyl ether in the volume fraction range of 1%~40%.
    • Formula (2): Yⱼ = aⱼAⱼ + bⱼ
    • Where: Yⱼ—volume fraction of oxygenate component j, %; Aⱼ—peak area of oxygenate component j; aⱼ, bⱼ—slope and intercept of the calibration curve for oxygenate component j.
    • The correlation coefficient of the calibration curve for each component obtained by the least squares method shall not be less than 0.990. If the correlation coefficient does not meet the requirement, the calibration samples shall be retested or the instrument conditions and hardware equipment shall be checked.
• 12 Calculation
  • 12.1 System 1—— Quantification of hydrocarbon composition in pure hydrocarbon liquefied petroleum gas: use the calibration normalization method, and calculate the volume fraction of the hydrocarbon component to be measured according to formula (3).
    • Formula (3): Vᵢ = (Kᵢ × Aᵢ) / Σ(Kᵢ × Aᵢ) × 100 (the original formula source-text extraction is unclear in the source text, requires confirmation against the source standard (source-text extraction))
    • Where: Vᵢ—volume fraction of hydrocarbon component i in the pure hydrocarbon liquefied petroleum gas sample, %; Kᵢ—correction factor of hydrocarbon component i in the pure hydrocarbon liquefied petroleum gas sample, see formula (1); Aᵢ—peak area of hydrocarbon component i in the pure hydrocarbon liquefied petroleum gas sample; ΣKᵢAᵢ—the sum of the products of the correction factors and peak areas of the n hydrocarbon components to be measured.
  • 12.2 System 2—— Quantification of composition of liquefied petroleum gas containing oxygenates
    • 12.2.1 Calculate the volume fraction Yⱼ of the oxygenate component to be measured according to the calibration curve equation in formula (2).
    • 12.2.2 Calculate the volume fraction Vᵢ of each hydrocarbon component to be measured by the subtraction calibration normalization method according to formula (4).
      • Formula (4): Vᵢ = (Kᵢ × Aᵢ) / Σ(Kᵢ × Aᵢ) × (100 - ΣYⱼ) (the original formula source-text extraction is unclear in the source text, requires confirmation against the source standard (source-text extraction))
      • Where: Vᵢ—volume fraction of hydrocarbon component i in the liquefied petroleum gas sample containing oxygenates, %; Kᵢ—correction factor of hydrocarbon component i in the liquefied petroleum gas sample containing oxygenates, see formula (1); Aᵢ—peak area of hydrocarbon component i in the liquefied petroleum gas sample containing oxygenates; ΣKᵢAᵢ—the sum of the products of the correction factors and peak areas of the n hydrocarbon components in the liquefied petroleum gas sample containing oxygenates; ΣYⱼ—the sum of the volume fractions of the m oxygenates to be measured.
      • Note: When using system 2 to calculate the hydrocarbon composition in pure hydrocarbon liquefied petroleum gas, the term ΣYⱼ in formula (4) is 0.
  • 12.3 Calculation method: According to the calculation method used in this standard, it may be completed by manual calculation. However, to simplify the data processing procedure, it is recommended to use a computer program for implementation.

10. Precision

• The precision data of this standard come from the test results of 9 laboratories on 10 mixed liquefied petroleum gas samples containing different component content levels. According to the requirements of the GB/T 6683 method, the precision of the method was determined through statistical calculation. Judge the reliability of the sample results according to the following provisions (95% confidence level).
• 14.1 Repeatability (r): The difference between two test results obtained by the same operator using the same instrument for continuous determination of the same sample shall not exceed the repeatability limit in Table 3 to Table 4.
• 14.2 Reproducibility (R): The difference between two single, independent results obtained by different laboratories and different operators using different instruments for the same sample shall not exceed the reproducibility limits in Table 3 and Table 4.
• Table 3 Repeatability and reproducibility of hydrocarbon components (% volume fraction):
  • Ethane: content range 0.01~3; repeatability (r) 0.108X^0.9824 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.215X^0.745 (requires confirmation against the source standard (source-text extraction))
  • Propane: content range 0.05~95; repeatability (r) 0.098X^0.920 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.145X^0.600 (requires confirmation against the source standard (source-text extraction))
  • Propylene: content range 0.01~95; repeatability (r) 0.039X^0.78 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.235X^1.31 (requires confirmation against the source standard (source-text extraction))
  • Isobutane: content range 0.05~80; repeatability (r) 0.056X^1.0 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.100X^0.64 (requires confirmation against the source standard (source-text extraction))
  • n-Butane: content range 0.2~99; repeatability (r) 0.086X^2 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.148X^0.403 (requires confirmation against the source standard (source-text extraction))
  • trans-2-Butene: content range 0.01~40; repeatability (r) 0.100X^2.5 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.147X^0.745 (requires confirmation against the source standard (source-text extraction))
  • Isopentane: content range 0.01~3; repeatability (r) 0.100X^0.8 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.167X^0.81 (requires confirmation against the source standard (source-text extraction))
  • 1-Pentene: content range 0.01~0.5; repeatability (r) 0.197X^1.08 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.359X^1.151 (requires confirmation against the source standard (source-text extraction))
  • Note: X is the average of the volume fractions of two determination results, %.
• Table 4 Repeatability and reproducibility of oxygenate components (% volume fraction):
  • Dimethyl ether: content range 1~40; repeatability (r) 0.202X^2 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.398X^0.971 (requires confirmation against the source standard (source-text extraction))
  • Methyl tert-butyl ether: content range 0.01~1; repeatability (r) 0.142X^0.8 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.188X^0.7 (requires confirmation against the source standard (source-text extraction))
  • Methanol: content range 0.01~1; repeatability (r) 0.238X^2.0 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.465X^2 (requires confirmation against the source standard (source-text extraction))
  • Acetone: content range 0.01~1; repeatability (r) 0.148X^1.6 (requires confirmation against the source standard (source-text extraction)); reproducibility (R) 0.438X^1.7 (requires confirmation against the source standard (source-text extraction))
  • Note: X is the average of the volume fractions of two determination results, %.
• 14.3 Bias: Because there is no suitable reference material, the bias of this method has not been determined.

11. Report

• Report the volume fractions of each hydrocarbon composition and/or oxygenate component in the liquefied petroleum gas sample. C₅ olefins and components above C₆ may be given as combined peaks in the analysis results, and the results shall be accurate to 0.01%.

12. Normative References

• GB/T 5274/ISO 6142 Gas analysis—Preparation of calibration gas mixtures—Gravimetric method
• GB 11174 Liquefied petroleum gas
• GB/T 12576 Calculation method for vapor pressure, relative density and octane number of liquefied petroleum gas
• GB 19159 Automotive liquefied petroleum gas
• SH/T 0233 Sampling method for liquefied petroleum gas
• References: [1] GB/T 6683 Method for determining precision data of petroleum product test methods

13. Source and verification

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14. Quick Reference for Questions and Answers