SH/T 0061-1991 Determination of magnesium content in lubricating oils (atomic absorption spectrometry)

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Card type: Test method

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

• Standard number: SH/T 0061-91
• Full title: Determination of magnesium content in lubricating oils (atomic absorption spectrometry)
• English title: not provided in the available source
• Replacement relationship: not provided in the available source
• Other: approved by 1991-06-28, implemented by 1992-07-01; confirmed in (2001)
• Reference adoption: Federal Republic of Germany national standard DIN 51431 T1(86) "Direct determination of magnesium content in lubricating oils by atomic absorption spectrometry"

2. Scope of application and non-applicability

• Applicable to the determination of magnesium content in lubricating oils, concentration range 0.02%～0.3%(m/m).
• This standard is also applicable to the determination of magnesium content in additives.
• Not applicable: not provided in the available source.

3. Method principle

After the sample is diluted with solvent naphtha, it is directly sprayed into the flame of an atomic absorption spectrometer, and the absorbance is measured. The absorbance of the sample is compared with the absorbance of the reference solution to calculate the magnesium content in the sample.

4. Reagents and materials (purity / preparation)

4.2 Materials

• a. Air: purified, oil-free and water-free.
• b. Acetylene gas: purity 99.9%.
• c. Solvent naphtha: complies with the provisions of SH 0005.
• d. White oil: complies with the provisions for oil No. 15 in SH 0007.
• e. Petroleum sodium sulfonate: sodium content known.

5 Reagents

• 5.1 Organometallic magnesium salt: analytical reagent, magnesium content known.
• 5.2 2- ethylhexanoic acid: chemical reagent.

6 Preparatory work

• 6.1 Prepare blank solution: weigh a certain amount of petroleum sodium sulfonate and dissolve it in 1L solvent naphtha so that the sodium content in the solution is about 200 mg/mL (requires confirmation against the source standard (source-text extraction), the source text reads "200W mLo").
  • Note: When the sodium content of the petroleum sodium sulfonate is 4%(m/m), weigh about 5g petroleum sodium sulfonate.
• 6.2 Prepare magnesium standard stock solution: weigh an appropriate amount of organometallic magnesium salt standard sample (accurate to 0.1mg) into a 100mL beaker, add 6mL 2- ethylhexanoic acid, stir and heat to dissolve, cool to room temperature, add white oil to 50g, store in a brown glass bottle; this solution is a magnesium standard stock solution of about 5000mg/kg.

5. Instruments and equipment

4.1 Instruments

• a. Atomic absorption spectrometer: wavelength range 190～900nm; any atomic absorption spectrometer capable of measuring the analytical line of magnesium within the absorbance range 0.1～0.5 is suitable.
• b. Magnesium hollow cathode lamp.
• c. Volumetric flasks: 25, 1000mL.
• d. Pipettes: 0.5, 1, 2, 5mL.
• e. Beaker: 100mL.
• f. Balance: sensitivity 0.1mg.

6. Recommended operating conditions

Operate the instrument according to the conditions in Table 2:

Note: The performance of different instrument models varies; the above conditions are for reference only.

7. Sampling and sample preparation

• 7.2 Prepare sample solution: accurately weigh 0.1～0.3g sample (accurate to 0.1mg) into a 25mL volumetric flask, dilute to the mark with blank solution, shake well and set aside for measurement.
• Note ②: For trace analysis, the sample amount may be increased to 2g (accurate to 0.1mg), and an appropriate amount of white oil should be added to the standard sample so that the viscosities of the standard solution and the sample solution are basically consistent.

8. Analytical procedure

• 7.1 Prepare standard working solutions: pipette an appropriate amount of magnesium standard stock solution into a 25mL volumetric flask, dilute with blank solution so that it reaches the concentration given in Table 1.
  • Table 1: the table content at source-text extraction in the source text is missing (concentration values require confirmation against the source standard (source-text extraction)).
  • Note ①: The standard working solutions must be prepared on the day of the test;
  • Note ②: The magnesium standard working solutions may be brought to the required concentration by two dilutions.
• 7.3 Measure absorbance:
  • 7.3.1 Operate the instrument according to the conditions in Table 2.
  • 7.3.2 Set zero with the blank solution.
  • 7.3.3 Measure the standard solution with the lowest magnesium content.
  • 7.3.4 Measure the standard solution with medium magnesium content.
  • 7.3.5 Measure the standard solution with the highest magnesium content.
  • 7.3.6 Measure the absorbance of the sample solution, continuously measuring twice.
  • 7.3.7 Measure the standard solution with the highest magnesium content.
  • 7.3.8 Measure the standard solution with medium magnesium content.
  • 7.3.9 Measure the standard solution with the lowest magnesium content.
  • 7.3.10 Set zero with the blank solution.
  • 7.3.11 Repeat steps 7.3.3～7.3.10, and use the average of the two absorbance values as the measurement result.
  • Note ①: For high-content samples exceeding the measurement range (such as the determination of additives), measurement may be carried out by changing the optical path length, reducing the weighed sample amount, or dilution.
  • Note ③: During the interval between measurements of the reference solution and the sample solution, the blank solution must be continuously sprayed in to maintain constant measurement conditions.

9. Qualitative and quantitative determination and calculation formula

The magnesium content in the sample X[%(m/m)] is calculated according to the following formula:

X = (A / A₀) × C × f × 25 × 100 × 10⁻³ / (m × 0.1) (requires confirmation against the source standard (source-text extraction), formula layout has noise)

Where:

• A—— average absorbance of magnesium in the sample solution;
• A₀ — average absorbance of the standard solution with magnesium concentration close to that in the sample;
• C—— concentration of the standard solution corresponding to A₀ (the concentration unit is illegible in the source transcription and remains unverified);
• f—— dilution factor;
• m—— sample mass, g;
• 25—— sample solution volume, mL.

10. Precision

Use the following provisions to judge the reliability of test results (95% confidence level).

Repeatability: The difference between two results obtained by repeated determination by the same operator shall not exceed the value specified in Table 3.

Table 3

Reproducibility: The difference between two results submitted by different laboratories shall not exceed the value specified in Table 4.

Table 4

11. Report

Take the arithmetic mean of two repeated determination results as the determination result. If the result is equal to or greater than 0.1%(m/m), take two decimal places; if the result is less than 0.1%(m/m), take three decimal places.

12. Referenced documents

• SH 0005 Solvent naphtha for the paint industry
• SH 0007 White oil for cosmetics

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