SH/T 0712-2002 Determination of iron content in gasoline (atomic absorption spectrometry)

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Card type: Test method

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

• Standard number: SH/T 0712-2002
• Chinese full name: Determination of iron content in gasoline (atomic absorption spectrometry)
• English name: Standard test method for iron in gasoline by atomic absorption spectroscopy
• Replacement relationship: not provided in the available source
• Issued/implemented: issued by 2002-05-31, implemented by 2002-07-01
• Issuing authority: State Economic and Trade Commission
• Technical committee: Sinopec Research Institute of Petroleum Processing
• Drafting organization: Sinopec Research Institute of Petroleum Processing
• Main drafters: He Jing, Wang Xia

2. Applicable scope and non-applicability

• Applicable to the determination of total iron content in gasoline.
• Iron content determination range: 2.0 mg/L～25.0 mg/L (1.1).
• Also applicable to gasoline containing methyl tert-butyl ether (MTBE), methyl tert-amyl ether (TAME), and ethanol (1.2).
• The determination of iron content in gasoline with other concentration ranges or containing other oxygenates has not been tested (1.2).
• This standard does not purport to address all of the safety concerns associated with its use. Users should establish appropriate safety precautions and determine appropriate regulations before use (1.3).

3. Method principle

The gasoline sample is treated with iodine-toluene solution, diluted with methyltrioctylammonium chloride-methyl isobutyl ketone (MIBK) solution, and the iron content in the sample is determined by atomic absorption spectrometer at 248.3 nm (Chapter 3 Method summary).

4. Reagents and materials (purity / preparation)

• 6.1 Reagent purity: Unless otherwise specified, analytical grade reagents should be used. If reagents of other grades are used, their purity should not reduce the accuracy of the determination.
• 6.2 Crystalline iodine.
• 6.3 Toluene. Warning: Toluene is flammable and harmful if inhaled. Appropriate ventilation should be provided to avoid inhalation and skin contact.
• 6.4 Iodine-toluene solution (0.03 g/mL): Dissolve 3 g crystalline iodine in toluene and dilute to 100 mL. (Note: The original text source-text extraction is "3.[unreadable character]", suspected to be "3 g", requires confirmation against the source standard (source-text extraction))
• 6.5 Dicyclopentadienyl iron (common name: ferrocene, C10H10Fe): purity not less than 95% (m/m), should be dried and stored at room temperature.
• 6.6 Methyltrioctylammonium chloride: purity not less than 90% (m/m).
• 6.7 Methyl isobutyl ketone (MIBK). Warning: Methyltrioctylammonium chloride and MIBK are moderately toxic. Ventilation should be provided during use to avoid inhalation and skin contact.
• 6.8 10% (V/V) Methyltrioctylammonium chloride-MIBK solution: Dissolve 88.0 g (100 mL) methyltrioctylammonium chloride in MIBK and dilute to 1 L.
• 6.9 1% (V/V) Methyltrioctylammonium chloride-MIBK solution: Dissolve 8.8 g (10 mL) methyltrioctylammonium chloride in MIBK and dilute to 1 L.
• 6.10 Solvent naphtha: meets the requirements of SH 0005.

5. Instruments and equipment

• 5.1 Atomic absorption spectrometer: capable of background correction, equipped with an iron hollow cathode lamp, for determining iron content in gasoline at 248.3 nm.
• 5.2 Volumetric flasks: 50 mL, 100 mL, 250 mL, 1000 mL.
• 5.3 Pipettes: 0.5 mL, 5.0 mL.
• 5.4 Glass beakers: 100 mL.

6. Recommended operating conditions

• Measurement wavelength: 248.3 nm.
• Flame: lean flame (9.1).
• Instrument background correction function is required to subtract the interference effect of organic substances on the determination (9.1).
• Adjust instrument parameters according to the instructions in the instrument operation manual, adjust the nebulizer, acetylene gas, and air flow rates to obtain a lean flame (9.1).
• If the curve is bent, readjust the sample introduction amount or gas flow rate until good linearity is obtained (9.2).

7. Sampling and sample preparation

• Sampling should be carried out in accordance with the requirements of GB/T 4756. Gasoline samples should be taken directly into light-protected containers and analyzed as soon as possible (Chapter 8).
• Sample preparation (10.1～10.3): In a 50 mL volumetric flask containing 30 mL MIBK, add 5.0 mL gasoline sample with a pipette and shake well; add 0.1 mL iodine-toluene solution to the volumetric flask with a 0.5 mL pipette, shake well, and react for about 1 min; add 5.0 mL 1% (V/V) methyltrioctylammonium chloride-MIBK solution, dilute to the mark with MIBK, and shake well.

8. Analysis procedure

• Preparation work:
  • 7.1 Prepare iron standard solution A (264.20 mg/L): Accurately weigh ferrocene 0.231 g (accurate to 0.1 mg) into a 100 mL beaker, dissolve with 10% (V/V) methyltrioctylammonium chloride-MIBK solution, transfer the solution to a 20 mL volumetric flask, dilute to the mark with 10% (V/V) methyltrioctylammonium chloride-MIBK solution, and shake well. (Note: The original text source-text extraction is "20mL volumetric flask", the conversion relationship with 264.20 mg/L requires confirmation against the source standard (source-text extraction))
  • 7.2 Prepare iron standard solutions B, C, D (5.28 mg/L, 13.21 mg/L and 26.42 mg/L): Accurately pipette 1.0 mL, 2.5 mL and 5.0 mL iron standard solution A into three 50 mL volumetric flasks, respectively add 5.0 mL 1% (V/V) methyltrioctylammonium chloride-MIBK solution, then dilute to the mark with MIBK.
  • 7.3 Prepare iron standard working curve solutions (0.53 mg/L, 1.32 mg/L and 2.64 mg/L): In four 50 mL volumetric flasks, respectively add 30 mL MIBK and 5.0 mL solvent naphtha, three of the volumetric flasks are respectively added with 5.0 mL iron standard solution B, C and D, and the other is used as a blank. Use a 0.5 mL pipette to respectively add 0.1 mL iodine-toluene solution to these four volumetric flasks, shake well, react for about 1 min, then add 5.0 mL 1% (V/V) methyltrioctylammonium chloride-MIBK solution, and dilute to the mark with MIBK.
• Calibration (Chapter 9):
  • 9.1 Instrument adjustment: Adjust instrument parameters according to the instructions in the instrument operation manual, adjust the nebulizer, acetylene gas, and air flow rates to obtain a lean flame. Determine iron content at 248.3 nm. Since organic substances generate a large background interference signal during combustion, the instrument background correction function is required to subtract the interference effect of organic substances on the determination and obtain accurate results.
  • 9.2 Sequentially aspirate the iron standard working curve solutions, record the absorbance, draw the standard working curve, and check the data linearity. If the curve is bent, readjust the sample introduction amount or gas flow rate until good linearity is obtained.
• Test procedure (Chapter 10):
  • 10.1 In a 50 mL volumetric flask containing 30 mL MIBK, add 5.0 mL gasoline sample with a pipette and shake well.
  • 10.2 Use a 0.5 mL pipette to add 0.1 mL iodine-toluene solution to the volumetric flask, shake well, and react for about 1 min.
  • 10.3 Add 5.0 mL 1% (V/V) methyltrioctylammonium chloride-MIBK solution, dilute to the mark with MIBK, and shake well.
  • 10.4 Sequentially aspirate the iron standard working curve solutions and the test sample solution, and record the absorbance values.
  • Note: Since the absorbance changes with time, the iron standard working curve solutions and the sample should be determined simultaneously.

9. Qualitative and quantitative determination and calculation formula

Calculate the iron content in the sample according to formula (1)) (mg/L), accurate to 0.1 mg/L:

Iron content = C × V₁ / V₂

Where:

• C: iron concentration in the sample solution read from the standard working curve, mg/L;
• V₁: sampling volume, according to clause 10.1, is 5.0 mL;
• V₂: dilution volume, according to clause 10.1, is 50.0 mL.

(Note: The original formula source-text extraction is "Iron content = C x [unreadable variable]", the variable subscripts and formula form require confirmation against the source standard (source-text extraction))

10. Precision

Judge the reliability of the results according to the following provisions (95% confidence level) (Chapter 12).

• 12.1 Precision: Through interlaboratory statistical investigation, according to GB/T 6683 standard, the precision of the method is as follows:
  • 12.1.1 Repeatability: For the same operator, using the same instrument, under constant operating conditions, the difference between two consecutive test results on the same sample shall not exceed the following value: 0.65X^0.9 (where X is the average of the two results, mg/L). (Note: The original text source-text extraction is "0.65X0.0", the exponent requires confirmation against the source standard (source-text extraction))
  • 12.1.2 Reproducibility: For different operators working in different laboratories, the difference between two independent test results on the same sample shall not exceed the following value: 0.55X^0.9 (where X is the average of the two results, mg/L). (Note: The original text source-text extraction is "0.55X0'9", the exponent requires confirmation against the source standard (source-text extraction))
• 12.2 Bias: Because there is no suitable reference material, the bias of this method cannot be determined.

11. Report

not provided in the available source.

12. Reference Documents

• GB/T 4756 Petroleum liquids—Manual sampling
• GB/T 6683 Petroleum products—Determination of precision data in relation to methods of test
• SH 0005 Solvent naphtha for paint industry

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