NB/SH/T 0711-2019 Determination of manganese content in gasoline by atomic absorption spectrometry

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Card type: Test method

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

• Standard number: NB/SH/T 0711—2019
• Chinese name: Determination of manganese content in gasoline by atomic absorption spectrometry
• English name: Standard test method for manganese in gasoline by atomic absorption spectroscopy
• Replacement relationship: replaces SH/T 0711—2002 "Method for determination of manganese content in gasoline (atomic absorption spectrometry)"
• Adoption relationship: modified adoption using the redrafting method of ASTM D3831-12(2017) "Standard test method for manganese content in gasoline (atomic absorption spectrometry)"
• Publication/implementation: published on 2019-06-04, implemented on 2019-10-01
• Publishing unit: National Energy Administration
• Drafting unit: Sinopec Research Institute of Petroleum Processing; participating drafting units: Shenzhen Institute of Metrology and Quality Inspection, CNOOC Huizhou Petrochemical Co., Ltd.
• Secretariat: National Technical Committee for Standardization of Petroleum Products and Lubricants, Subcommittee on Petroleum Fuels and Lubricants (SAC/TC280/SC1)
• Previous versions: SH/T 0711—2002

2. Scope of application and non-application

• Applicable to gasoline samples with a manganese mass concentration range of 0.25 mg/L ~ 25 mg/L, where manganese exists in the form of methylcyclopentadienyl manganese tricarbonyl (MMT).
• Applicable to gasoline containing methyl tert-butyl ether at a volume fraction not greater than 15%, or ethanol gasoline at a volume fraction not greater than 12%.
• The applicability to gasoline samples with an olefin volume fraction greater than 24% has not been investigated.
• Not applicable/not verified: other concentration ranges, MMT in other substances, and the determination of manganese compounds present in other forms in gasoline have not been verified by tests.

3. Method principle

The gasoline sample is treated with bromine solution or iodine-toluene solution, and diluted with methyl isobutyl ketone (MIBK) or methyltrioctylammonium chloride-MIBK solution. The manganese content is determined using an air-acetylene flame in an atomic absorption spectrometer at 279.5 nm. For the operating procedures of the atomic absorption spectrometer, see GB/T 15337.

4. Reagents and materials (purity / preparation)

• 6.1 Reagent purity: unless otherwise specified, all tests use analytical grade reagents.
• 6.2 Bromine.
• 6.3 Cyclohexane.
• 6.4 Bromine solution: add bromine to an equal volume of cyclohexane. (Warning: bromine causes severe burns on contact with skin; protective gloves are required for preparation, and good ventilation is required for preparation, storage, and use.)
• 6.5 Crystalline iodine.
• 6.6 Toluene.
• 6.7 Iodine-toluene solution (0.03 g/mL): dissolve 3.0 g crystalline iodine in toluene and dilute to 100 mL. (Warning: toluene is flammable and harmful if inhaled.)
• 6.8 Methyl isobutyl ketone (MIBK). (Warning: flammable, vapors are toxic.)
• 6.9 Methyltrioctylammonium chloride: mass fraction not less than 90%. (Warning: vapors are toxic.)
• 6.10 Volume fraction 10% methyltrioctylammonium chloride-MIBK solution: dissolve 88.0 g (100 mL) methyltrioctylammonium chloride with MIBK and dilute to 1 L.
• 6.11 Volume fraction 1% methyltrioctylammonium chloride-MIBK solution: dissolve 8.8 g (10 mL) methyltrioctylammonium chloride with MIBK and dilute to 1 L.
• 6.12 Blank gasoline: manganese mass concentration lower than 0.12 mg/L. (Note: if confirmation is needed, it may be determined by atomic absorption spectrometry or plasma emission spectrometry after extraction and enrichment, or confirmed by other feasible methods.)
• 6.13 Manganese standard substance: manganese sulfonate or manganese chloride (MnCl₂·4H₂O), or a commercially available pre-made organometallic manganese stock solution that meets the requirements.
• 6.14 264.2 mg/L Manganese standard stock solution: dissolve an appropriate amount of manganese sulfonate or a commercially available organometallic manganese standard substance in MIBK, or dissolve a certain amount of manganese chloride with volume fraction 10% methyltrioctylammonium chloride-MIBK solution (6.10) to prepare a manganese standard stock solution of 264.2 mg/L.
• 6.15 Manganese standard solutions of 5.3 mg/L, 13.2 mg/L, 26.4 mg/L: accurately pipette 1.0 mL, 2.5 mL and 5.0 mL mass concentration of 264.2 mg/L manganese standard stock solution (6.14) into 50 mL volumetric flasks; when using manganese sulfonate or a commercially available organometallic manganese standard substance, directly add MIBK (6.8) and dilute to the mark; when using manganese chloride, add 5.0 mL volume fraction 1% methyltrioctylammonium chloride-MIBK solution (6.11), then dilute to the mark with MIBK (6.8). (Note: the mass concentrations required by 6.14 and 6.15 are recommended concentrations; different mass concentrations may be selected according to actual sample conditions without affecting accuracy.)
• 6.16 Quality control (QC) samples: it is best to use one or more stable, representative gasoline samples.

5. Instruments and equipment

• 5.1 Atomic absorption spectrometer: expandable and equipped with a manganese hollow cathode lamp or a continuous light source lamp containing a manganese analytical line, used to observe the absorption spectrum of manganese at 279.5 nm, a premix slot burner with a rotatable front end and an adjustable nebulizer. (Warning: harmful; toxic and explosive substances may be present; please refer to the relevant safety hazards in the instrument manufacturer's instructions.)
• 5.2 Sample bottles: maximum capacity 40 mL, with polyethylene or polytetrafluoroethylene caps or glass stoppers.
• 5.3 Volumetric flasks: 50 mL.
• 5.4 Pipettes: 5.0 mL.
• 5.5 Micropipettes: 100 μL.
• 5.6 Automatic pipette or pipette with the same function: can pipette 9.0 mL of solution.

6. Recommended operating conditions

• 8.3.1 Observe the manganese absorption spectrum at 279.5 nm according to the manufacturer's recommended operating conditions for an air-acetylene flame atomic absorption spectrometer. The recommended procedure is as follows; because each spectrometer design is different, it may not be applicable to specific instrument settings.
• 8.3.1 Aspirate MIBK (6.8), adjust the nebulizer efficiency, acetylene and air flow rates to obtain a lean flame.
• 8.3.1 When preparing manganese working standard solutions with bromine solution (6.4), use MIBK (6.8) as the blank, and sequentially aspirate 3 manganese working standard solutions (8.1.3); when preparing manganese working standard solutions with iodine-toluene solution (6.7), use the reagent blank (8.2.3) as the blank, and sequentially aspirate 3 manganese working standard solutions (8.2.3), recording each absorbance in sequence.
• Note: record the absorbance and check the linearity of the data. If it is not linear (R²<0.995), readjust the sample or acetylene flow rate, slightly adjust the tilt state, and then repeat the calibration until the absorbance is linear. Rotating the burner head to reduce absorbance may help achieve linearity.
• Measurement wavelength: 279.5 nm; flame: air-acetylene flame (lean flame).

7. Sampling and sample preparation

• Take gasoline samples in accordance with the specifications of GB/T 4756 or GB/T 27867, and pour into a light-protected container. Analyze as soon as possible after sampling.
• Warning: MMT in gasoline is chemically unstable under light. If the gasoline sample is exposed to light during analysis, it may lead to low or unstable results.
• Sample treatment (bromine solution method, 9.1): 9.1.1 add 9.0 mL MIBK into the sample bottle; 9.1.2 use a micropipette to add 100 μL bromine solution into the sample bottle; 9.1.3 add 1.0 mL gasoline sample, shake the sample bottle to mix evenly with the bromine solution.
• Sample treatment (iodine-toluene solution method, 9.2): 9.2.1 in a 50 mL volumetric flask containing 30 mL MIBK, use a pipette to add 5.0 mL gasoline sample, and shake well; 9.2.2 use a micropipette to add 100 μL iodine-toluene solution into the volumetric flask, shake well, and react for about 1 min; 9.2.3 when using manganese sulfonate or a commercially available organometallic manganese standard substance, directly dilute to the mark with MIBK and shake well; when using manganese chloride, add 5.0 mL volume fraction 1% methyltrioctylammonium chloride-MIBK solution, then dilute to the mark with MIBK and shake well.

8. Analysis procedure

• 8.1 Prepare manganese working standard solutions using bromine solution (6.4):
  • 8.1.1 Pipette 9.0 mL MIBK (6.8) into three sample bottles.
  • 8.1.2 Use a micropipette to add 100 μL bromine solution (6.4) into 3 sample bottles respectively.
  • 8.1.3 Pipette 1.0 mL of the 5.3 mg/L, 13.2 mg/L and 26.4 mg/L manganese standard solutions (6.15) prepared with manganese sulfonate or a commercially available organometallic manganese standard substance into 3 sample bottles, shake the sample bottles to mix evenly with the bromine solution. In this way, the manganese standard solutions are diluted by a factor of 10, consistent with the sample dilution factor.
• 8.2 Prepare manganese working standard solutions using iodine-toluene solution (6.7):
  • 8.2.1 In 4 50 mL volumetric flasks, add 30 mL MIBK (6.8) and 5.0 mL blank gasoline (6.12) respectively.
  • 8.2.2 To each of the 3 volumetric flasks, respectively add 5.0 mL 3 manganese standard solutions of different concentrations (6.15), and use another as the reagent blank.
  • 8.2.3 Using a micropipette, add 100 μL iodine-toluene solution (6.7) to these 4 volumetric flasks, shake well, and react for about 1 min. When using manganese sulfonate or a commercially available organometallic manganese certified reference material as the standard material for measurement, directly dilute to the mark with MIBK (6.8). When using manganese chloride as the standard material for measurement, add 5.0 mL volume fraction 1% methyltrioctylammonium chloride-MIBK solution (6.11), then dilute to the mark with MIBK (6.8).
• 8.3 Instrument preparation: see the recommended operating conditions in Section 6.
• 9.1 Treat the sample with bromine solution (6.4): 9.1.1 Add 9.0 mL MIBK into the sample bottle; 9.1.2 Using a micropipette, add 100 μL bromine solution into the sample bottle; 9.1.3 Add 1.0 mL gasoline sample, shake the sample bottle to mix it uniformly with the bromine solution; 9.1.4 Aspirate and spray the sample solution, and record the absorbance.
  • Note 1: When establishing the working curve with working standard solutions treated with bromine solution, treat the sample with bromine solution.
  • Note 2: The absorbance of samples left standing for a long time will change over time, so the absorbance of the prepared manganese working standard solutions and sample solutions must be measured promptly.
• 9.2 Treat the sample with iodine-toluene solution (6.7): 9.2.1 In a 50 mL volumetric flask containing 30 mL MIBK, use a pipette to add 5.0 mL gasoline sample, and shake well; 9.2.2 Using a micropipette, add 100 μL iodine-toluene solution to the volumetric flask, shake well, and react for about 1 min; 9.2.3 When using manganese sulfonate or a commercially available organometallic manganese certified reference material, directly dilute to the mark with MIBK and shake well; when using manganese chloride, add 5.0 mL volume fraction 1% methyltrioctylammonium chloride-MIBK solution, then dilute to the mark with MIBK and shake well; 9.2.4 Aspirate and spray the sample solution, and record the absorbance (see 9.1.4 Note 2).
  • Note: When establishing the working curve with working standard solutions treated with iodine-toluene solution, treat the sample with iodine-toluene solution.

9. Qualitative and Quantitative Determination and Calculation Formulas

• 10.1 The concentration of manganese in the sample can be read directly from the instrument. Alternatively, plot the best working curve of absorbance versus manganese concentration, and read the manganese concentration of the sample from the working curve.
• Report the manganese content in the gasoline sample: when the result is less than 1 mg/L, take two significant figures; when the result is greater than 1 mg/L, round to 0.1 mg/L.
• Precision calculation formulas:
  • Repeatability (r): r = 0.3308(X₁ + 0.1062), where X₁ is the average of two replicate test results, in units of mg/L.
  • Reproducibility (R): R = 1.650(X₂ + 0.1062), where X₂ is the average of two single independent test results, in units of mg/L.

10. Precision

• 12.1 Precision: Use the following provisions to judge the reliability of test results (95% confidence level).
• 12.1.1 Repeatability (r): For continuous determinations of the same sample by the same operator using the same instrument under the same operating conditions, the difference between the two test results obtained shall not exceed the calculated value of formula (1). r = 0.3308(X₁ + 0.1062), where X₁ is the average of two replicate test results, in units of mg/L.
• 12.1.2 Reproducibility (R): For determinations of the same sample by different operators in different laboratories using the correct method, the difference between the two single and independent test results obtained shall not exceed the calculated value of formula (2). R = 1.650(X₂ + 0.1062), where X₂ is the average of two single independent test results, in units of mg/L.
• 12.2 Bias: Because there is no suitable reference material, the bias of this method cannot be determined.

11. Report

• 10.1 The concentration of manganese in the sample can be read directly from the instrument. Alternatively, plot the best working curve of absorbance versus manganese concentration, and read the manganese concentration of the sample from the working curve. Report the manganese content in the gasoline sample: when the result is less than 1 mg/L, take two significant figures; when the result is greater than 1 mg/L, round to 0.1 mg/L.
• Quality control (Chapter 11): 11.1 Use stable and representative related samples as quality control samples (QC), and determine the reliability of the analytical test process by analyzing QC samples; 11.2 When the laboratory's quality control/quality assurance (QA) protocols have been established, these protocols can be used to confirm the reliability of test results; 11.3 When the laboratory has not established quality control/quality assurance protocols, refer to Appendix A; 11.4 For further explanation of QC/QA, refer to ASTM D6792.
• Appendix A (Informative appendix) Quality control: A.1 Use of QC samples (A.1.1~A.1.4); A.2 Selection of QC samples; A.3 QC and control chart techniques (see NB/SH/T 0843 for details).

12. Normative References

• GB/T 4756 Manual sampling of petroleum liquids
• GB/T 15337 General rules for atomic absorption spectrometry
• GB/T 27867 Automatic pipeline sampling of petroleum liquids
• NB/SH/T 0843 Statistical techniques for the evaluation of analytical testing systems in the petrochemical industry
• ASTM D6792 Guidelines for quality systems in testing laboratories for petroleum products and lubricants (Practice for Quality System in Petroleum Products and Lubricants Testing Laboratories)

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