NB/SH/T 0838-2010 Determination of polycyclic aromatic (PCA) content in unused lubricating base oils and asphaltene-free petroleum distillates — Dimethyl sulfoxide extraction refractive index method

Summary page. This page is a compiled excerpt/summary of the standard — it is not the full standard text and does not replace it. Verify every value against the official standard and the product certificate before use.

NB/SH/T 0838-2010 specifies the determination of polycyclic aromatic (PCA) content in unused lubricating base oils and asphaltene-free petroleum distillates by dimethyl sulfoxide extraction with refractive index evaluation, and this page summarizes its identity, scope, apparatus, reagents, sampling branches, extraction, evaporation, calculation and precision.

Evidence note: original method learning material based on the 2010 original of the same edition; the numbers listed serve for limited comparison with the original figures, and complete technical review is pending. This is not the full standard text or a controlled operating procedure; no specific product applicability is inferred, and method precision is not batch certificate uncertainty.

Identity of the edition and adoption relationship: Original PDF physical pages 1, 2. This material is based on NB/SH/T 0838—2010, published on 1 May 2010 and implemented on 1 October 2010. The original foreword states modification adoption of IP 346/96, and adds referenced documents, a designed pre-treatment vacuum distillation apparatus, and adjusted cleaning and result reporting descriptions; this cannot be inferred as complete technical equivalence or applicability of the present IP version. The specific official record lists this edition as current, and item 118 of the Energy Administration list agrees with the cover in number and both dates; this metadata does not replace the original technical document or independent technical acceptance.

Scope and object of measurement: Original PDF physical page 3. Original 1.1 applies to unused lubricating base oils without additives, with a fraction below 300 °C at standard atmospheric pressure 101.3 kPa of not more than 5% recovered volume fraction, and a PCA content range of 1%–15% mass fraction. Other asphaltene-free petroleum distillates or PCA outside the range can be measured, but original 1.2 does not establish their precision. The original PCA definition includes three or more fused aromatic rings and the corresponding sulfur- and nitrogen-containing compounds; PCA is not directly equated with total aromatics, nor is regulatory compliance of a product judged on that basis.

Division of roles between extraction and refractive evaluation: Original PDF physical pages 3, 6, 7. The sample is diluted with cyclohexane and, if necessary, first distilled; it is extracted twice with DMSO at 23 ± 2 °C, then separated with brine and cyclohexane, washed, dried, freed of solvent and the residue weighed. The mass gives the PCA extract content, and the refractive index is used to evaluate the aromaticity of the residue; the two results have different roles, neither refractive index is taken as a mass fraction, and no material selection or product applicability commitment is provided.

Apparatus and value ranges: Original PDF physical pages 3, 4. Original 5.4 Abbe refractometer has a range of 1.30–1.71 and operating conditions of 25–80 °C; the rotary evaporator water bath is at most 80 °C and the oil bath at most 110 °C. The 50/250/1000 mL round-bottom flasks and 250/1000 mL separatory funnels have separate uses; 5.9 analytical balance is accurate to 0.1 mg. The distillation column is 500 mm long with reflux control and vacuum measurement; the complete Figure 1 assembly, calibration and safety have not been reconstructed, and equipment cannot be manufactured or accepted from this summary.

Reagents and their original preparation: Original PDF physical pages 4, 5. Cyclohexane, DMSO and anhydrous sodium sulfate are among the original reagent requirements; DMSO is clear and colourless, with a purity of not less than 99.5% mass fraction and water not higher than 0.1% mass fraction. Original 6.4 treats at a minimum of 21 °C with 900 mL DMSO and 70 mL cyclohexane, separates the lower layer and stores it sealed; this is method reagent handling, not a storage commitment for any product on sale. Original 6.11 dissolves 80 g sodium chloride in 2 kg water and calls it 4% mass fraction; the connection between the two exact mass fractions awaits technical verification, and the formulation is not changed on the author's behalf.

Sampling and the three pre-treatment branches: Original PDF physical page 5. Sample according to GB/T 4756; original 7.2 does not place or store the sample in plastic containers, to avoid loss of light fractions through the wall. First check the boiling range according to GB/T 6536 or GB/T 9168: a fraction below 300 °C of not more than 5% recovered volume may continue directly; 5%–95% goes to vacuum distillation residue; more than 95% reports the corresponding distillation range and states that the extract content was not determined. The original a/b wording overlaps exactly at 5%, and no automatic algorithm is added; these are method branches for samples and are not extrapolated to all product storage and transport. Original 8.1 branch | Recovered volume below 300 °C | Original route a | Not more than 5% | May continue the test without pre-treatment b | 5%–95% | Use the residue after vacuum distillation c | More than 95% | Report the distillation range and that the extract was not determined

Limited study of the distillation pre-treatment: Original PDF physical pages 5, 6. Original 8.2 weighs 250 g to within 1 g in a 1000 mL flask, purges with nitrogen at 15 L/h for 10 min, evacuates to 2 kPa and then holds 2 L/h; reflux starts at 1:1, changes to 2:1 at the atmospheric-pressure equivalent of 280 °C, and collection stops at the equivalent of 310 °C. The corresponding actual vacuum temperature requires Annex B, and 280/310 °C must not be taken directly as the measured temperature at the top of the vacuum column. The original reflux off/on times of 2 s and 4 s are examples only; cool to 50–70 °C before restoring atmospheric pressure, and the original distillation mass loss does not exceed 5 g. The complete control and table look-up have not been reconstructed, and this is not an apparatus operating procedure.

Sample homogenization and glassware: Original PDF physical page 6. Original 8.4 heats viscous or waxy samples while stirring, to a maximum of 90 °C, and filters before use only if solid remains after heating; 8.5 measures the kinematic viscosity at 100 °C for the later evaporation branch. Original 9.1 avoids grease contamination by using PTFE stopcocks and sleeves; glassware is dried at 70–80 °C after cleaning, and the rotary evaporator is cleaned with 200 mL distilled toluene. Method cleaning and temperatures are not product storage, shelf life or purity certificates.

Two DMSO extractions: Original PDF physical page 6. Original 10.1 weighs 3.85–4.15 g of sample to within 0.1 mg and transfers it quantitatively to funnel A with a total of 45 mL cyclohexane. Two 100 mL portions of treated DMSO are used for separate extractions, shaking at 23 ± 2 °C for 1 min at about 100 shakes, with at least 20 min for the first to reach complete separation; collect the lower layer into a 1 L flask B, and rinse the glass wool with 10 mL DMSO. These two extractions and the subsequent two cyclohexane extractions are different and the number of times or the upper/lower phases must not be interchanged.

Brine phase transfer and drying: Original PDF physical pages 6, 7. Original 10.5 adds 40 mL cyclohexane and 400 mL of the brine originally called 4% to funnel B and shakes for 2 min; this step generates heat and pressure, and the original requires venting 2–4 times in the first 1 min, under ventilation and away from the face. The lower layer goes to C and the cyclohexane upper layer to D; C is extracted again with 40 mL cyclohexane and combined with D. Then wash with two 25 mL portions of brine at about 70 °C and dry over 5 g anhydrous sodium sulfate. Complete solvent, pressure and waste safety requires controlled documents, and this paragraph is not a stand-alone safety procedure.

Staged evaporation and refractive index measurement: Original PDF physical page 7. Original 10.9 uses a bath at 80 °C and a pressure of 1.5 ± 0.5 kPa, transferring to a weighed 50 mL flask when 15–17 mL remains; 10.11 generally continues evaporation for 1 h. If the original sample has a kinematic viscosity at 100 °C greater than 15 mm²/s, the original note first holds 80 °C at the same pressure for 15 min, then 105–110 °C at about 0.2 kPa for 1 h; the two routes must not be merged into one universal condition. Cool for 5 min before releasing the vacuum, clean the outer wall, and weigh to within 0.1 mg after 30 min at room temperature. The refractive index is normally measured at 25 °C, and at 80 °C only for very viscous or solid extracts; sample handling temperatures are not product storage conditions.

The three calculation relationships and the role of mass: Original PDF physical pages 7, 8. With pre-distillation, original equation (1) X=100(C−B)/[A₁(1+D/R)]; without distillation, equation (2) X=100(C−B)/A₂. X is the PCA extract mass fraction in %, A₁ the distillation residue used for extraction and A₂ the weighed sample without distillation; B is the mass of the empty 50 mL flask with glass beads, C the total of that flask, the glass beads and the extract; D and R are the masses of the light fraction and the residue separated by pre-distillation, both defined in mg in the original. R here is the residue mass and must not be confused with the reproducibility. Original equation (3) nD25 = nD80 + 0.0222; this is the refractive index temperature conversion of this method and not a converter for arbitrary product parameters.

Reporting and precision range: Original PDF physical page 8. Original 12 reports the PCA extract mass fraction to 0.1%, and for base oils present in sufficient quantity also reports the refractive index to 0.001; original 12.2 states that when the actual content is below 0.05% the textual report is less than 0.1%, the two thresholds differ, and this rule must not be changed into a fixed detection limit or a branch added for exactly 0.05%. Original 13 gives, at the 95% confidence level, PCA repeatability 0.112x^0.7 and reproducibility 0.228x^0.7, where x is the mean of two content results; refractive index r 0.004/R 0.028. The original collaborative study covered 7 laboratories and 4 samples, PCA 1.5%–14.5%, refractive index 1.574–1.674, with typical samples having 95% recovered volume above 300 °C. It cannot be extrapolated to samples outside the original 1.2 range or taken as product batch certificate uncertainty. Original Table 1 item | Repeatability r | Reproducibility R PCA extract | 0.112x^0.7 | 0.228x^0.7 Refractive index | 0.004 | 0.028

Annexes, references and unverified areas: Original PDF physical pages 2, 3, 9, 10. Annex A, the clause cross-reference, and Annex B, the temperature-pressure table, are both informative. Annex B is a dense conversion table for six pressure groups of 0.13/0.27/0.67/1.33/2.67/6.7 kPa, not transcribed cell by cell nor made into interpolation software. The original cites GB/T 265, GB/T 4756, GB/T 6536, GB/T 9168 and SH/T 0724; the citations and adoption notes do not prove that present versions are equivalent or that a specific product applies. The 22 physical pages serve only for scope location and for the root figures and numerical comparisons listed, not for full technical review; the complete distillation-extraction flow path, all cells of Table B, instrument calibration, hazardous chemicals and waste disposal controlled procedures, and independent Hermes/Grok technical acceptance remain to be completed. Original Table 2 PCA content (mass fraction %) | Typical r | Typical R 1 | 0.1 | 0.2 3 | 0.2 | 0.5 5 | 0.3 | 0.7 7 | 0.4 | 0.9 9 | 0.5 | 1.0 11 | 0.6 | 1.2 13 | 0.6 | 1.3 15 | 0.7 | 1.5

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