GB/T 12575-1990 Determination of vanadium content in liquid fuel oils (flameless atomic absorption spectrometric method)

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Card type: Test method

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

• Standard number: GB/T 12575-90
• Chinese full title: Determination of vanadium content in liquid fuel oils (flameless atomic absorption spectrometric method)
• English name: Liquid fuel oils - Determination of vanadium content - Flameless atomic absorption spectroscopic method
• Replacement relationship: not provided in the available source
• Approval/implementation: approved by the State Bureau of Technical Supervision 1990-12-14, implemented on 1991-10-01
• Reference adoption: Federal Republic of Germany national standard DIN 51790 third edition (1978) "Determination of vanadium content in liquid fuel oils"

2. Scope of application and non-applicability

• Applicable to the determination of vanadium content from 0.4 to 4.0 mg/kg in marine fuel oils and heavy fuel oils, etc.
• Note: After appropriate treatment of the sample, it is also applicable to the determination of liquid fuel oils with a vanadium content less than 0.4 mg/kg or greater than 4.0 mg/kg (see Appendix A).
• Non-applicable scope: not provided in the available source.

3. Method principle

After the sample is burned in a crucible, it is ashed in a high-temperature furnace at 600℃, then the ash residue is dissolved with hydrochloric acid to prepare a sample solution, and then measured with a flameless atomic absorption spectrometer.

4. Reagents and materials (purity / preparation)

• 4.1 Ammonium metavanadate: analytical reagent.
• 4.2 Hydrochloric acid: analytical reagent.
• 3.2.1 Argon: purity not less than 99.9%.
• 3.2.2 Deionized water.
• 5.1 Hydrochloric acid solution: prepare a 4% (m/m) hydrochloric acid solution to be used as the blank solution.
• 5.2 Preparation of vanadium standard stock solution: accurately weigh 233.5 mg ammonium metavanadate (NH₄VO₃) into a beaker, dissolve with the blank solution, transfer to a 1 L volumetric flask, and dilute to the mark. This solution is a vanadium-containing standard stock solution of 100 mg/kg.
• 6.1 Vanadium working solution: according to Table 1, take different amounts of vanadium standard stock solution into 100 mL volumetric flasks, dilute to the mark with the blank solution, and prepare vanadium working solutions with the concentration ranges listed in Table 1. Note: The working solutions used in the determination should be freshly prepared.

Table 1 Vanadium working solution

5. Instruments and equipment

• 3.1.1 Atomic absorption spectrometer: any model of atomic absorption spectrometer equipped with a graphite furnace and a program controller.
• 3.1.2 Vanadium hollow cathode lamp.
• 3.1.3 Volumetric flasks: 5, 10, 25, 50, 100 mL, 1 L.
• 3.1.4 Pipettes: 1, 2, 5, 10, 20, 50 mL.
• 3.1.5 Microsyringe: 10, 20 μL (original text is "10, 20L", requires confirmation against the source standard (source-text extraction)).
• 3.1.6 Constant-temperature water bath: capable of maintaining 60 to 70℃.
• 3.1.7 Balance: sensitivity 0.1 mg.
• 3.1.8 Crucible: made of platinum or quartz, with a lid, capacity 50 mL.
• 3.1.9 High-temperature furnace: capable of controlling temperature at 600±25℃.

6. Recommended operating conditions

• 6.2.1 Atomic absorption spectrometer: use a vanadium hollow cathode lamp, select wavelength 318.4 nm. Fine adjustment should be made near this wavelength to obtain maximum light intensity. No deuterium compensator is required.
• 6.2.2 Flameless atomizer: after a new graphite tube is installed, the positions of the vanadium hollow cathode lamp, graphite tube, and sleeve support, etc., must be adjusted to obtain the best values. Note: The proportional relationship between absorbance and concentration depends on the graphite tube used each time; therefore, the same set of data must be measured on the same graphite tube.
• 6.2.3 Adjust the protector and cooling water.
• 6.4 Operate the instrument according to the conditions in Table 2.

Table 2 Typical instrument operating conditions

Note: The performance of different models of instruments varies; the above conditions are for reference only (the wording of this qualification is unclear in the source transcription and requires verification).

7. Sampling and sample preparation

• 6.3 Preparation of sample solution: preheat the sample in a water bath to 40 to 60℃, then shake vigorously to homogenize it, and in a clean, weighed quartz (or platinum) crucible, weigh 2 to 4 g of sample, weighed to within 0.01 g (original text "0.018", requires confirmation against the source standard (source-text extraction)). Heat the crucible so that the sample burns uniformly; after burning is complete, transfer to a 600±25℃ high-temperature furnace and maintain at 1 to 2 h to ash completely. Dissolve the ash remaining in the crucible with 3 mL hydrochloric acid solution (clause 5.1), then cover with a lid and heat to 60 to 70℃, maintain for 30 min, and weigh after cooling (remove the crucible lid before weighing). If the vanadium content of the sample is higher than 1 mg/kg, it must be transferred to an appropriate volumetric flask and diluted before measurement.

8. Analytical procedure

• 6.5 Measurement of absorbance:
  • 6.5.1 Zero the instrument with the blank solution.
  • 6.5.2 Measure the absorbance of the vanadium working solutions: the working solutions should be injected into the graphite tube in order from low to high concentration; between measurements of standard solutions of different concentrations, the graphite tube must be cleaned.
  • 6.5.3 Draw the working curve for the optimal range of 0.2 to 1.0 mg/kg.
  • 6.5.4 Measure the absorbance of the sample solution: the measurement conditions for the sample solution are the same as for the working solutions.
  • 6.5.5 Zero the instrument with the blank solution.
  • 6.5.6 Repeat steps 6.5.2 to 6.5.4. Use the average of the two absorbance values as the determination result.

9. Qualitative and quantitative determination and calculation formulas

• 7.1 When the vanadium content in the sample is greater than 1 mg/kg and the sample needs to be diluted after acid dissolution, the vanadium content in the sample X₁ (mg/kg) is calculated according to formula (1):

  X₁ = (E · C · m₁) / (E₁ · m) … (1)

  Where:

  • E—— Absorbance of the sample solution;
  • E₁ — absorbance of the standard solution with a vanadium concentration similar to that of the sample solution;
  • C—— Concentration of the vanadium standard working solution, mg/kg;
  • m₁ — mass of the sample after dilution, g;
  • m—— Mass of the sample, g.

• 7.2 When the vanadium content in the sample is less than or equal to 1 mg/kg and the sample does not need to be diluted after acid dissolution, the vanadium content in the sample X (mg/kg) is calculated according to formula (2):

  X = (E · C · m₁) / (E₁ · m) … (2)

  Where: m₁ — mass of the sample after dissolution with hydrochloric acid solution, g. (Note: The original formula (2) source-text extraction is incomplete, with only fragments such as "Ei·m" visible; the above formula has been organized according to the isomorphic form of formula (1) and the context, requires confirmation against the source standard (source-text extraction).)

• Round the vanadium content result of the sample to 0.05 mg/kg (original text "0.05m8/K8", requires confirmation against the source standard (source-text extraction)).

10. Precision

When the vanadium content in the sample is from 0.4 to 4.0 mg/kg, the reliability of the test results shall be judged according to the following provisions (95% confidence level).

• 8.1 Repeatability: the difference between two results obtained by the same operator in repeated determinations shall not exceed 0.1 mg/kg.
• 8.2 Reproducibility: the difference between two results submitted by different laboratories shall not exceed 0.2 mg/kg.

Appendix A Supplementary provisions for samples with vanadium content greater than 4.0 mg/kg or less than 0.4 mg/kg (reference item)

• A1 Sample treatment and calculation
  • A1.1.1 When the vanadium content in liquid fuel oil is greater than 4.0 mg/kg, use the method of reducing the sample weight or further diluting the sample solution.
  • A1.1.2 When the vanadium content in liquid fuel oil is less than 0.4 mg/kg, use the method of increasing the sample weight or not diluting the sample solution.
• A2 Calculation
  • A2.1 When calculating the vanadium content in a sample of A1.1.1, calculate according to formula (1) in clause 7.1 of this standard.
  • A2.2 When calculating the vanadium content in a sample of A1.1.2, calculate according to formula (2) in clause 7.1 of this standard.
• A3 Precision (for precision when the vanadium content in liquid fuel oil is less than 0.4 mg/kg or greater than 4.0 mg/kg, refer to the following values)
  • A3.1 Repeatability (r): the difference between two results obtained by the same operator in repeated determinations shall not exceed the value in Table A1.
  • A3.2 Reproducibility (R): the difference between two results submitted by two laboratories shall not exceed the value in Table A1.

Table A1 (mg/kg)

Note: This precision is based on statistical tests of 38 samples from three laboratories after analysis.

11. Report

not provided in the available source.

12. Normative References

not provided in the available source (the list of normative references is not listed in the main text).

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