SH/T 0228-1992 Determination of barium, calcium, and zinc content in lubricating oils (atomic absorption spectrometry)

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Card type: Test method

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

• Standard number: SH/T 0228-92
• Chinese title: Determination of barium, calcium, and zinc content in lubricating oils (atomic absorption spectrometry)
• English title: not provided in the available source
• Replacement relationship: replaces ZB E60 007—89
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20
• Reference adoption: Federal Republic of Germany national standard DIN 51391 (81) T1 "Direct determination of barium, calcium, and zinc content in lubricating oils by atomic absorption spectrometry"

2. Scope of application and non-applicability

• Applicable to: barium, calcium, and zinc content in unused lubricating oils.
• Concentration ranges:
  • Barium: 0.1~0.8% (m/m)
  • Calcium: 0.03~0.4% (m/m)
  • Zinc: 0.02~0.16% (m/m)
• Not applicable to: oils containing aluminum additives and acetate additives.

3. Method principle

The sample is diluted with an organic solvent in a certain proportion and directly sprayed into the flame of an atomic absorption spectrometer to measure absorbance. The absorbance of the sample is compared with the absorbance of the reference solution to calculate the barium, calcium, and zinc content in the sample.

4. Reagents and materials (purity / preparation)

4.1 Materials

• Air: purified, oil-free and water-free.
• Acetylene gas: purity 99.9%.
• Solvent naphtha: meets the requirements for qualified product in SH 0005.
• White oil: meets the requirements for grade 15 in SH 0007.

4.2 Reagents

• Sodium dodecyl sulfonate: chemically pure.
• Benzyltrimethylammonium chloride: chemically pure.
• Barium cyclohexylbutyrate: barium content known.
• 2- calcium ethylhexanoate: calcium content known.
• Zinc cyclohexylbutyrate: zinc content known (the source source-text extraction writes "zinc cyclohexylbutyrate" as "zinc cyclohexylbutyrate", requires confirmation against the source standard (source-text extraction)).
• 2- ethylhexanoic acid: chemically pure.

4.3 Solution preparation

• Blank solution (6.1): weigh about 0.18 g benzyltrimethylammonium chloride (the source source-text extraction writes "benzyltrimethylammonium chloride" as "benzyltrimethylammonium chloride", requires confirmation against the source standard (source-text extraction)) and 1 g sodium dodecyl sulfonate, dissolve in 1 L solvent naphtha, and heat in a 95±5 ℃ water bath until saturated; use the clear liquid when in use.
• Barium, calcium, and zinc standard stock solution (6.2): respectively weigh appropriate amounts of barium, calcium, and zinc standard samples into a 100 mL beaker (weighed to 0.1 mg), add 6 mL 2- ethylhexanoic acid, stir and heat to dissolve, cool to room temperature, add white oil to 50 g, and store in a brown glass bottle; this solution is a 5000 ppm barium, calcium, and zinc standard stock solution.

5. Instruments and equipment

• Atomic absorption spectrophotometer: wavelength range 190–900 nm, capable of measuring the analytical lines of barium, calcium, and zinc within the absorbance range 0.1–0.5.
• Barium hollow cathode lamp, calcium hollow cathode lamp, zinc hollow cathode lamp.
• Volumetric flasks: 25 mL, 1000 mL.
• Pipettes: 1, 2, 5, 10 mL.
• Graduated cylinders: 5 mL, 1000 mL.
• Water bath: capable of maintaining constant temperature at 95±5 ℃.
• Balance: sensitivity 0.1 mg.

6. Recommended operating conditions

Operate the instrument according to the conditions in Table 2 (source note: instrument performance varies among different models; the above conditions are for reference only):

Note: In Table 2, the acetylene flow rate "2-3", extraction amount "2-6" for Ca, and the burner height for Zn are missing or unclear in the source, requires confirmation against the source standard (source-text extraction).

7. Sampling and sample preparation

• Prepare sample solution (7.2): accurately weigh 0.1~0.3 g sample (accurate to 0.1 mg) into a 25 mL volumetric flask, dilute to the mark with blank solution, shake well and set aside for measurement.
• High-content samples (exceeding the measurement range, such as additive determination): can be measured by changing the optical path length, reducing the sample weight, or dilution.
• Trace analysis: the sample amount can be increased to 2 g, and an appropriate amount of white oil is added to the standard sample so that the viscosity of the standard working solution and the sample solution are basically consistent.

8. Analytical procedure

8.1 Prepare standard working solutions (7.1)

Respectively take appropriate amounts of barium, calcium, and zinc standard stock solutions into 25 mL volumetric flasks, dilute with blank solution to reach the concentrations given in Table 1.

Table 1 Concentrations of standard working solutions (μg/mL):

Note: ① The standard working solutions must be prepared on the day of the test. ② The calcium and zinc standard working solutions can be brought to the required concentrations by secondary dilution.

8.2 Measure absorbance (7.3)

1. Operate the instrument according to the conditions in Table 2.
2. Zero the instrument with the blank solution.
3. Measure the absorbance of the standard working solution with the lowest barium, calcium, and zinc content.
4. Measure the absorbance of the standard working solution with medium barium, calcium, and zinc content.
5. Measure the absorbance of the standard working solution with the highest barium, calcium, and zinc content.
6. Measure the absorbance of the sample solution, continuously measuring twice.
7. Measure the absorbance of the standard working solution with the highest barium, calcium, and zinc content.
8. Measure the absorbance of the standard working solution with medium barium, calcium, and zinc content.
9. Measure the absorbance of the standard working solution with the lowest barium, calcium, and zinc content.
10. Zero with blank.
11. Repeat steps 7.3.3~7.3.10, and use the average of the two absorbance values as the measurement result.

9. Qualitative and quantitative determination and calculation formula

The barium, calcium, and zinc content X [% (m/m)] in the sample is calculated according to the following formula:

X = (A / A₀) × C × 25 / (f × m × 10⁶) × 100

Where:

• A—— average absorbance of barium, calcium, and zinc in the sample solution;
• A₀ — average absorbance of the standard working solution with barium, calcium, and zinc concentrations close to those in the sample;
• C—— concentration of the standard working solution corresponding to A₀, μg/mL;
• f—— dilution factor;
• m—— sample mass, g;
• 25—— sample volume, mL.

(The source formula source-text extraction contains noise; the symbols shall be interpreted according to the context, requires confirmation against the source standard (source-text extraction).)

10. Precision

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

10.1 Repeatability (Table 3)

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

10.2 Reproducibility (Table 4)

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

11. Report

Take the arithmetic mean of two repeated measurement results as the measurement result; if the result is greater than 0.10% (m/m), take two decimal places; if the result is less than 0.10% (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 Q&A reference