SH/T 0076-1991 Test for furfural in lubricating oils

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.

Source limitations: The confirmation year, several units and symbols, and the reference-solution cross-reference remain uncertain. The available card gives conflicting reference-solution clauses; the difference is flagged below. It gives reporting rules below and above 10 mg/kg but does not specify the rule for exactly that value. Check the original standard before use.

Card type: Test method

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

• Standard number: SH/T 0076-91
• Chinese title, translated: Test for furfural in lubricating oils
• English name: not found in the available source.
• Replacement relationship: from the implementation date of this standard, the former national standard GB 390-77 (confirmed in 1988), Test for furfural in lubricating oils, is superseded.
• Confirmation year: the source shows '(200( ) year of confirmation)'; the exact year requires verification against the original standard.
• Additional information: technically administered by the Research Institute of Petroleum Processing; drafted by Dalian Petrochemical Company; principal drafters: Liu Shilan and Li Shuhui.
• Approval/implementation: approved by China Petrochemical Corporation on 1991-11-26; implemented on 1992-12-01.

2. Scope and exclusions

• This standard specifies a qualitative method for detecting furfural in lubricating base oils.
• Applies to lubricating base oils.
• Exclusions: not found in the available source.

3. Principle

• Aniline hydrochloride reacts with furfural to form a red compound. Dilute the sample, extract the furfural with water, then use aniline hydrochloride to determine qualitatively whether furfural is present in the aqueous extract.
• Informative Appendix A principle: furfural in the sample reacts with aniline acetate to form a pink product. Measure the absorbance of the coloured solution with a spectrophotometer to determine the sample furfural content.

4. Reagents and materials (purity / preparation)

• 5.1 Petroleum ether: 90—120℃, analytical grade; alternatively, straight-run gasoline with a boiling range of 80—140℃.
• 5.2 Aniline hydrochloride: analytical grade.
• 4.2.1 Filter paper: industrial filter paper of 130 g/m². The extracted string '130g/[unreadable unit]' requires verification against the original standard.
• 4.2.2 Distilled water.
• 6.1 Preparation of test paper: moisten the filter paper with a 10%—15% aqueous solution of aniline hydrochloride.
• Appendix A reagents:
  • A4.1 Furfural: analytical grade.
  • A4.2 Aniline: analytical grade.
  • A4.3 Acetic acid: analytical grade.
  • A4.4 Toluene: analytical grade.
• A5.1.1 Purification of furfural: distil 100 mL of commercially available analytical-grade furfural. Discard the first 20 mL of distillate, then collect 50 mL for use. The source states that purified furfural generally reaches 90% purity. Store in an amber glass narrow-neck bottle in a cool, ventilated place. Do not use if it becomes dark yellow.
• A5.1.2 Preparation of furfural standard solutions: weigh (0.1054±0.0002) g of purified furfural and dissolve in freshly produced straight-run diesel. Transfer to a 250 mL volumetric flask, dilute to the mark with freshly produced straight-run diesel and mix. The source states that this standard solution contains 0.417 mg of furfural per millilitre. Using a microburette, transfer 6 mL of this solution to another 250 mL volumetric flask, dilute to the mark with straight-run diesel and mix. The stated concentration of this solution is 0.01 mg of furfural per millilitre.
• A5.2.1 Purification of aniline: distil 100 mL of analytical-grade aniline. Discard the first 10 mL of distillate and the final 10 mL of residue. Store the intermediate 80 mL of colourless distillate in an amber glass narrow-neck bottle in a cool, ventilated place.
• A5.2.2 Preparation of aniline acetate solution: slowly add freshly distilled aniline to acetic acid in a glass narrow-neck bottle, using an aniline-to-acetic-acid volume ratio of 1:9. During mixing, immerse the bottle in an ice bath, keep the solution below 20℃ without freezing, and stir. Note: prepare aniline acetate on the day of use. If it turns yellow, prepare it again.
• A3.2 Material: straight-run diesel with a solidification point below 10℃.

5. Apparatus

• 4.1.1 Separating funnel: 250 mL.
• 4.1.2 Conical flasks: 50 and 100 mL.
• 4.1.3 Beakers: 50 and 100 mL.
• 4.1.4 Graduated cylinders: 25 and 50 mL.
• Appendix A apparatus:
  • A3.1.1 Spectrophotometer: capable of measuring absorbance at a wavelength of 520 nm, with 10 mm and 20 mm absorption cells. The extracted '20[unreadable character]' requires verification against the original standard.
  • A3.1.2 Volumetric flasks: 25 and 250 mL.
  • A3.1.3 Burette: 25 mL, graduated in 0.1 mL divisions, with a spare bottle and a rubber double bulb for pressurizing the liquid.
  • A3.1.4 Microburettes: 2 mL with 0.01 mL minimum divisions; 10 mL with 0.05 mL minimum divisions.
  • A3.1.5 Pipettes: 2 mL with 0.02 mL divisions; 5 mL with 0.05 mL divisions; 10 mL with 0.1 mL divisions.
  • A3.1.6 Stoppered test tubes: 2 mL.
  • A3.1.7 Graduated cylinders: 25 and 100 mL.
  • A3.1.8 Distillation apparatus: a 100 mL glass distillation flask with matching condenser and receiver.
  • A3.1.9 Wide-mouth insulated flask.
  • A3.1.10 Amber glass narrow-neck bottles: 50 and 100 mL.

6. Recommended operating conditions

• Qualitative test: heat the sample to 40—45℃ and shake for 5 min. Carefully shake the mixture in the separating funnel for 5 min, then allow the phases to separate.
• Appendix A spectrophotometric method: wavelength 520 nm. Colour development is strongest within 1—3 min after adding aniline acetate solution, so develop and measure samples individually. Temperature affects the result; keep the sample measurement temperature as close as possible to that used for the calibration curve. Prepare a calibration curve monthly, and prepare a new curve whenever the instrument is adjusted or the reagent batch changes.

7. Sampling and sample preparation

• 6.2 Sample preparation: sample in accordance with GB/T 4756. With the sample occupying no more than three-quarters of the bottle capacity, heat to 40—45℃, then shake for 5 min to mix thoroughly.
• Appendix A, A6.2: weigh the sample quantity specified in Table A1 into a 25 mL volumetric flask, to 0.0002 g.

Table A1

8. Procedure

• 7.1 Using a graduated cylinder, transfer 25 mL of the heated, mixed sample and 25 mL of petroleum ether or straight-run gasoline to the separating funnel and mix. Part of the solvent may be used to rinse the sample measuring cylinder, with the rinsings added to the separating funnel. Add 25 mL of distilled water. Carefully shake the mixture in the separating funnel for 5 min, allow the phases to separate, and drain the aqueous layer into a conical flask or beaker for use.
• 7.2 Using a clean glass rod, place several drops of the aqueous extract on the test paper and observe the colour change.
• Appendix A test procedure:
  • A6.1 In a 25 mL volumetric flask, add 10 mL of freshly prepared aniline acetate solution, dilute to the mark with toluene and mix to prepare the reference solution.
  • A6.2 In another 25 mL volumetric flask, weigh the sample quantity specified in Table A1, to 0.0002 g.
  • A6.3 Add 7—8 mL of toluene to dissolve the sample, then add 10 mL of freshly prepared aniline acetate solution. Dilute to the mark with toluene and mix.
  • A6.4 Measure the absorbance according to A5.3.4.
• Preparation of the calibration curve:
  • A5.3.1 Take six 25 mL volumetric flasks and add 7—8 mL of toluene to each. Using a microburette, add respectively 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mL of the 0.01 mg/mL furfural standard solution and mix.
  • A5.3.2 Add 10 mL of aniline acetate solution to each flask in turn and dilute to the mark with toluene. Stopper tightly and invert to mix. The resulting standard solutions contain respectively 0.005, 0.01, 0.015, 0.02, 0.025 and 0.03 mg of furfural.
  • A5.3.3 In another 25 mL volumetric flask, add 3 mL of the straight-run diesel used to prepare the standard solutions and 10 mL of acetic acid. Dilute to the mark with toluene to prepare a reference solution.
  • A5.3.4 Quickly transfer the solution from the volumetric flask to a 10 mm absorption cell and place it in the colorimeter optical path. The source says to use the A5.3.2 solution as reference and measure absorbance at 520 nm. This reference differs from the preceding reference-solution preparation clause and requires verification against the original standard; it has not been silently corrected here.
  • A5.3.5 Plot the calibration curve of furfural content (mg) against absorbance, or determine the regression equation relating absorbance and furfural content (mg).

9. Determination and calculation

• Qualitative assessment (section 8): allow the drops on the test paper to air-dry. Red colour where the aqueous extract was applied indicates furfural in the sample; absence of red colour indicates no furfural.
• Appendix A calculation:

  • A7.1 Use the absorbance measured under A6.4 to read the corresponding furfural content (mg) from the calibration curve, or calculate it using the regression equation.

  • A7.2 Calculate sample furfural content X (mg/kg) using equation (A1):

    X = (M / m) × 10³ …… (A1)

    Where:

    • M — furfural content corresponding to the measured absorbance, mg;
    • m — sample mass, g.

10. Precision

• Appendix A, A8 Precision (provisional):
  • A8.1 Repeatability: the difference between two repeat results obtained by the same operator shall not exceed 0.13(X+1.5) mg/kg.
  • A8.2 Reproducibility: the difference between two results submitted by different laboratories shall not exceed 0.25(X+1.5) mg/kg.
  • Note: X is the arithmetic mean of the two results.
• Precision for the qualitative test: not found in the available source.

11. Report

• Appendix A, A9 Report:
  • A9.1 Report the arithmetic mean of two repeat determinations as the sample furfural content.
  • A9.2 For results below 10 mg/kg, round to one decimal place; for results above 10 mg/kg, round to an integer. Report in mg/kg.
• Reporting requirements for the qualitative test: not found in the available source.

12. References

• GB/T 4756 Petroleum liquids — Manual sampling.

13. Source limitations and verification

• Source extraction uncertainties requiring verification:
  • The source text uses 'SH/T 0076-91', whereas the source index uses 'SHT-76-1991'. The designation in the body is 'SH/T 0076-91'.
  • The year in '(200( ) year of confirmation)' remains unverified.
  • The extracted '130g/[unreadable unit]' is interpreted by the source card as '130 g/m²'; verification pending.
  • The extracted '90[unreadable separator]12090' is interpreted by the source card as '90—120℃'; verification pending.
  • The extracted '40[unreadable separator]459C' is interpreted by the source card as '40—45℃'; verification pending.
  • The extracted 'loom[unreadable character]kg' is interpreted by the source card as '100 mg/kg'; verification pending.
  • The extracted '20[unreadable character] absorption cell' is interpreted by the source card as '20 mm absorption cell'; verification pending.
  • Division-unit strings '0.IML', 'O.OlmL', '0.05mLo' and '0.1MLo' require verification.
  • The extracted '1[unreadable separator]3.i.' is interpreted by the source card as '1—3 min'; verification pending.
  • Symbols and units in '0.13(X[unreadable sign]1.5 )mgi[unreadable character]' and '0.25(i + 1.5) mg/kgo' require verification.
  • The extracted 'G$ 390-77' is interpreted by the source card as 'GB 390-77'; verification pending.
  • 'IR3', '195' and '186' are page-number strings from the source.

14. Quick reference questions