NB/SH/T 0891-2014 Determination of soot content in used engine oils — Spectrophotometric method

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Card type: Test method

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

• Standard number: NB/SH/T 0891—2014
• Chinese full title: Determination of soot content in used engine oils — Spectrophotometric method
• English name: Spectrophotometric detection of soot in used engine oil samples
• Replacement relationship: not provided in the available source (the foreword only states "adopted by modification using the redrafting method from CEC L-82-97", and does not mention replacing any national standard)
• Adoption relationship: adopted by modification using the redrafting method from CEC L-82-97 "Determination of soot content in used engine oils — Spectrophotometric method"
• Technical differences from CEC L-82-97 (according to the foreword):
  • Deleted content related to CEC L-56-T-98
  • Deleted referenced standards ISO/IEC 17025 and ISO 5725
  • Deleted statements related to measurement uncertainty
  • Added warning information for cyclohexane and acetone
  • Deleted example statements and figures in the section on cleaning cuvettes
  • Deleted statements on sample handling
  • Deleted relevant data and figures from the analysis of international interlaboratory test results in the precision section
  • Editorial modifications were made according to China's standard drafting format; for structural differences see Appendix A
• Publication/implementation: published on 2014-06-29, implemented on 2014-11-01
• Issuing authority: National Energy Administration
• Secretariat: Subcommittee on Lubricating Oil Drain Intervals of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280/SC6)
• Drafting organization: Dalian Lubricating Oil Research and Development Center of PetroChina Company Limited
• Main drafters: Xie Pingping, Pang Cuicui, Liu Honghui, Chen Yuan

2. Scope of application and non-applicability

• This standard specifies a method for determining soot content in used engine oils by spectrophotometry.
• It is applicable to evaluating soot content in used engine oils, and is generally applicable to used engine oils with relatively high soot content (the soot content range examined for precision in this standard is 2.78%~6.89%, see Chapter 15).
• Not applicable: no explicit "not applicable" clause is provided in the available source; Chapter 15 states that test oils with soot content greater than 7% have poor repeatability and reproducibility, and whether test oils outside the range 2.78%~6.98% are valid has not been verified (Note: Chapter 1 of the source text writes 6.89%, while Chapter 15 writes 6.98%; the values are inconsistent and require confirmation against the source standard (source-text extraction)).

3. Method principle

Thoroughly mix the used engine oil test sample, use a spectrophotometer to measure the absorbance of the sample at 500 nm, or use a photoelectric colorimeter to measure the absorbance of the sample at 490 nm, and calculate the soot content in the used engine oil.

4. Reagents and materials (purity / preparation)

• 6.1 Reagents:
  • 6.1.1 Cyclohexane, analytical reagent, purity >99.5%. Warning: highly flammable, reacts strongly with oxidants and may even cause combustion.
  • 6.1.2 Acetone, industrial grade. Warning: highly flammable, toxic and harmful if inhaled or ingested.
• 6.2 Materials:
  • 6.2.1 Conical flask, 125 mL or 250 mL.
  • 6.2.2 Glass pipette, 20 mL (B grade or equivalent precision, tolerance 0.06 mL) single-mark/volumetric glass pipette; other volumetric measuring instruments of the same precision may also be used.
  • 6.2.3 Industrial detergent.
• Preparation method: not provided in the available source (no solution preparation steps are given).

5. Apparatus and equipment

• 5.1 Spectrophotometer, capable of measuring absorbance at 500 nm wavelength; or a photoelectric colorimeter (equipped with a green filter) to measure absorbance at 490 nm wavelength.
• 5.2 Glass or quartz cuvette, with an optical path length between parallel faces of 5 mm.
• 5.3 Paint shaker or mechanical shaker, optional, used to homogenize the sample.
• 5.4 Analytical balance, with a readability of 0.1 mg.
• Others: ultrasonic bath (see 10.1, used for cleaning cuvettes); magnetic stirrer and magnetic stir bar (see 9.4, used when necessary).

6. Recommended operating conditions

• Measurement wavelength: spectrophotometer 500 nm; photoelectric colorimeter 490 nm.
• Cuvette optical path length: 5 mm.
• Sample mass: 0.1 g ± 0.05 g (source text "0.1g 0.05g", requires confirmation against the source standard (source-text extraction)).
• Diluent: cyclohexane, measure an appropriate amount with a 20 mL glass pipette.
• Absorbance readings are retained to the second decimal place.
• The entire operation from sampling (9.2) to testing (9.7) shall be completed within 20 min ± 5 min.
• Instrument calibration: the spectrophotometer shall be calibrated at least once a year; when necessary, reference oils provided by the CEC SG-1-082 working group may be used to check the instrument.

7. Sampling and sample preparation

• 8.1 The soot content test of used engine oil shall be completed within one month after the engine test ends. The test date shall be stated in the result report; test results for samples tested more than one month after the engine test ends are invalid, but may be used for sample research.
• 8.2 Samples are stored at room temperature and shall be shaken uniformly before testing. If the sample is to be tested for 100 ℃ kinematic viscosity and soot content, it shall be placed in a 60 mL plastic bottle, and the distance from the liquid surface of the sample to the top of the container shall be greater than 1 cm, to avoid excessive air entrainment in the sample during shaking. If the sample is only tested for soot content, at least 5 mL of sample is required.
• 8.3 The test sample shall be mixed uniformly before sampling for testing; it may be shaken by hand for about 1 min, and a mechanical shaker or paint shaker is recommended. Sampling and weighing for testing shall be carried out promptly within 3 min ± 1 min after shaking the sample. If a commercially available mechanical shaker is used, it is recommended to mix the used oil sample uniformly as follows; the springs supporting the shaker should be able to simultaneously provide vertical motion of the sample:
  • 8.3.1 Tighten the lid of the sample container.
  • 8.3.2 Place the sample container on the mechanical shaker.
  • 8.3.3 Shake for 5 min ± 15 s (source text "5 min +15so", requires confirmation against the source standard (source-text extraction)).
  • 8.3.4 Remove the sample container from the mechanical shaker.
  • 8.3.5 Take a sample for testing.

8. Analytical procedure

• 9.1 Turn on the power of the spectrophotometer or photoelectric colorimeter, preheat the instrument according to the instrument instructions, and set zero.
• 9.2 Weigh 0.1 g ± 0.05 g of the used engine oil test sample, place it in a 125 mL or 250 mL conical flask, and record the sample mass to the fourth decimal place.
• 9.3 Use a 20 mL glass pipette to measure an appropriate amount of cyclohexane into the conical flask to dilute the sample; other equipment capable of adding a fixed volume of liquid may also be used, ensuring that the absorbance value of the sample is within the accurate measurement range of the instrument.
• 9.4 Shake the mixture of sample and solvent manually until uniform; when necessary, a stirrer and magnetic stir bar may be used to ensure that the sample is completely dissolved in cyclohexane.
• 9.5 Pour part of the sample solution into a clean glass cuvette, and use another glass cuvette to hold cyclohexane. If a single-beam spectrophotometer is used, first place the cuvette containing cyclohexane in the measurement cell as a reference and set zero, then measure the test sample. If a double-beam spectrophotometer is used, place the cuvette containing the test sample in the measurement cell and the cuvette containing cyclohexane in the reference cell.
• 9.6 Immediately measure the absorbance of the test sample at 500 nm wavelength (when using a photoelectric colorimeter, measure the absorbance of the test sample at 490 nm wavelength); record the absorbance value to the second decimal place.
• 9.7 If the absorbance value of the test sample exceeds the measurement range of the instrument, prepare the sample again, then measure an appropriate amount of cyclohexane to dilute the sample, ensuring that the measured absorbance value of the test sample is within the measurement range of the instrument. The entire operation from sampling (see 9.2) to testing (see 9.7) shall be completed within 20 min ± 5 min.
• 10 Cleaning cuvettes:
  • 10.1 Before each test, rinse the cuvette with the solvent cyclohexane to ensure that the cuvette is clean. During testing, it is necessary to clean the cuvette frequently; at least after every consecutive 10 tests, the cuvette shall be soaked in industrial detergent, cleaned in an ultrasonic bath, and then rinsed successively with distilled water and acetone.

9. Qualitative and quantitative determination and calculation formula

• 11.1 The soot content is calculated according to the following formula:

  Soot (%) = 7 × DOx × M1 / Mx

  Where:

  • n —— dilution factor (the correspondence between symbols and explanations in the source formula is suspected to have a source-text extraction misalignment, requires confirmation against the source standard (source-text extraction))
  • DOx —— absorbance value of the test sample
  • M1 —— 0.1000 g (ideal mass of the used oil sample)
  • Mx —— actual mass of the used engine oil sample

• 11.2 Soot content (%) is retained to the second decimal place.

• 12 Test evaluation: only soot content determinations that satisfy all test conditions in the above chapters are valid. Test results obtained more than one month after the engine test ends are invalid.

10. Precision

• Note: When determining precision, this standard selected only a portion of used engine oil types and is based on a small amount of data; therefore, results may differ for other test oils with different formulation compositions or different degrees of degradation. Test oils with soot content greater than 7% have poor repeatability and reproducibility. The precision data of this standard are applicable to test oils with soot content in the range 2.78%~6.98%; whether test oils outside this soot content range are valid has not been verified. Judge the reliability of test results according to the following provisions (95% confidence level).

• 15.1 Repeatability (r): In the same laboratory, by the same operator using the same instrument, under the same test conditions, for successive determinations on the same test sample, the difference between two test results obtained shall not be greater than the value in Table 1.

  Table 1 Repeatability

  Soot content/%	Repeatability/%
  2.78 ~ 6.89	r = X × 0.0184 − 0.0224

  Note: X is the arithmetic mean of the two replicate determination test results being compared, %.

• 15.2 Reproducibility (R): In different laboratories, by different operators using different instruments, for determinations on the same test sample, the difference between two single, independent test results obtained shall not be greater than the value in Table 2.

  Table 2 Reproducibility

  Soot content/%	Reproducibility/%
  2.78 ~ 6.89	R = X × 0.0512 + 0.0226

  Note: X is the arithmetic mean of the two single independent test results being compared, %.

11. Report

Report the following information:

• Cite this standard.
• Identification of the test sample.
• Soot content determination result (retained to the second decimal place).
• Validity of the test.
• Test date.

12. Normative references

• CEC L-93-04 Bench evaluation method for medium-temperature dispersancy of light-duty direct-injection diesel engine oils
• CEC L-83-97 Determination of kinematic viscosity of in-service oils 100 ℃
• Note: The foreword mentions deletion of referenced standards ISO/IEC 17025 and ISO 5725 (i.e., they are not referenced by this standard).
• Basis for drafting: GB/T 1.1—2009.

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