SH/T 0182-1992 Determination of copper content in light petroleum products (spectrophotometric method)

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Card type: Test method

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

• Standard number: SH/T 0182-92 (confirmed in 2000)
• Chinese title: Determination of copper content in light petroleum products (spectrophotometric method)
• English title: not provided in the available source
• Replacement relationship: replaces ZB E31012-88
• First issued: 1977; first revision in 1980 (see additional notes)
• Approval/implementation: approved by China Petrochemical Corporation in 1992-05-20, implemented in 1992-05-20

2. Scope of application and non-applicability

• Applicable to gasoline, jet fuel and other light petroleum products with olefin content less than 2%.
• Not applicable: not provided in the available source (only the limiting condition of olefin content less than 2% is given).

3. Method principle

The sample is oxidized and destroyed with sodium hypochlorite, and copper is extracted and separated with dilute hydrochloric acid. Then the sample is dissolved in a slightly alkaline solution, with ammonium citrate as a masking agent, in isooctane solvent, lead diethyldithiocarbamate reacts with copper ions to form a yellow complex, and colorimetric determination is carried out.

4. Reagents and materials (purity / preparation)

• 5.1 Hydrochloric acid: guaranteed reagent grade, prepared as 13%(m/m) hydrochloric acid solution.
• 5.2 Nitric acid: analytical reagent grade, prepared as a 1:1 solution by volume ratio.
• 5.3 Sodium hypochlorite solution (alkaline) (Antiformin): analytical reagent grade, active chlorine content not less than 50 g/L (the source source-text extraction is “50&/L”, requires confirmation against the source standard (source-text extraction)).
• 5.4 Ammonia water: analytical reagent grade.
• 5.5 Phenolphthalein indicator: prepared as 1 g/L phenolphthalein-ethanol indicator solution (the source source-text extraction is “1[unreadable characters]L”, requires confirmation against the source standard (source-text extraction)).
• 5.6 Copper sulfate (CuSO4·5H2O): analytical reagent grade.
• 5.7 Ammonium citrate: analytical reagent grade, weigh 20 g±0.1 g ammonium citrate and dissolve in 100 mL distilled water.
• 5.8 Hydroxylamine hydrochloride: analytical reagent grade, weigh 1 g±0.1 g hydroxylamine hydrochloride and dissolve in 100 mL distilled water (the source source-text extraction is “1[unreadable characters]0.1g”, requires confirmation against the source standard (source-text extraction)).
• 5.9 Sodium diethyldithiocarbamate: analytical reagent grade.
• 5.10 Lead nitrate: analytical reagent grade.
• 5.11 Isooctane (2,2,4- trimethylpentane): analytical reagent grade.
• 5.12 Distilled water: deionized water or redistilled water.
• 4.2 Materials: qualitative filter paper, diameter not greater than 9 cm.

5. Instruments and equipment

• 4.1.1 72 type spectrophotometer (or similar spectrophotometer): use a cuvette with an optical path of 3 cm.
• 4.1.2 Separatory funnel: 100, 250, 500, 1000 mL.
• 4.1.3 Volumetric flask: 1000 mL.
• 4.1.4 Pipette: 1, 2, 5, 10, 25 mL.
• 4.1.5 Beaker: 50 mL.
• 4.1.6 Hard glass sampling bottle: 2000 mL.

6. Recommended operating conditions

• Measurement wavelength: 438 nm (Note: because the wavelength accuracy of each instrument is not completely consistent, the wavelength with maximum absorbance should be selected near 438 nm for measurement).
• Reference: isooctane.
• Cuvette optical path: 3 cm.
• Amount of color-developing solution added: 10 mL.
• Shaking time: shake vigorously for 5 min.
• Preparation of color-developing solution: weigh 0.2 g sodium diethyldithiocarbamate and 0.2 g lead nitrate and 1 g ammonium citrate into a 100 mL beaker, add 50 mL water to dissolve (because the lead diethyldithiocarbamate produced by the reaction has relatively low solubility in water, a white precipitate will separate out), quantitatively transfer it to a 1000 mL separatory funnel, and add 2 drops of phenolphthalein-ethanol indicator solution, adjust with ammonia water until the solution just turns red, then add 500 mL isooctane, shake vigorously for 5 min. Put the aqueous phase into another 1000 mL separatory funnel, and add 500 mL isooctane, shake vigorously for 5 min, discard the aqueous phase (because lead diethyldithiocarbamate is in excess, after extraction some insoluble matter will still remain in the aqueous phase), wash the isooctane extracts in the two separatory funnels once each with 100 mL distilled water, discard the aqueous phase, combine the organic phases, filter through rapid qualitative filter paper into a brown bottle, and store in a dark place under refrigeration for later use.

7. Sampling and sample preparation

• 6.5 Sampling: clean and dry the hard glass sampling bottle. If sampling at a production unit, first open the sampling port in advance, discharge three to five times the amount equivalent to the “dead” corner retained oil, then sample directly into the sampling bottle, and immediately cap it. If sampling from an oil tank, carry out according to the requirements of GB/T 4756. The collected sample should be analyzed and measured within 24 h.
• 7.1 Determine the density of the sample at the test temperature according to GB/T 1884, and measure the sample that has been fully mixed in the sampling bottle according to the following table, and place it into a separatory funnel.

(Note: the original table source-text extraction has misalignment; the above table is arranged according to the original values, and some correspondences require confirmation against the source standard (source-text extraction))

8. Analysis procedure

• 6.3 Container copper removal: before use, a new separatory funnel must be soaked and washed with chromic acid cleaning solution, then shaken and washed with hot 1:1 nitric acid solution for 3 min, then rinsed with distilled water, and successively add 10 mL sodium hypochlorite solution, 20 mL 13%(m/m) hydrochloric acid solution; each time a reagent is added, shake for 5 min and continue to measure the absorbance according to the working curve plotting procedure in clause 6.4, repeat the above steps until the absorbance measured twice is basically consistent.
• 6.4 Plotting of the working curve: into six 100 mL separatory funnels, respectively add 0, 1.0, 3.0, 5.0, 7.0 and 9.0 mL copper standard solution with a content of 1 μg/mL, then successively add 5 mL ammonium citrate solution, 3 mL hydroxylamine hydrochloride solution, and shake well. Then add 2-3 drops of phenolphthalein-ethanol indicator solution, adjust with ammonia water until the test solution just turns red, then use a pipette to add 10 mL color-developing solution, shake vigorously for 5 min, and let stand to separate. After discarding the aqueous phase, filter the organic phase through qualitative filter paper into a cuvette, use isooctane as reference, and measure its absorbance with a 72 type spectrophotometer at 438 nm wavelength. The net absorbance obtained by subtracting the absorbance of the blank solution from the absorbance measured for each copper standard solution is used as the ordinate, and the corresponding micrograms of copper as the abscissa, to plot the working curve.
• 6.1 Preparation of copper standard solution: weigh 0.3928 g copper sulfate into a 50 mL beaker, dissolve with a small amount of distilled water, quantitatively transfer to a 1000 mL volumetric flask, and dilute to the mark with distilled water; the copper content in this solution is 0.1 mg/mL. Take 10 mL of the above solution and place it into a 1000 mL volumetric flask, dilute to the mark with distilled water; the copper content in this solution is 1 μg/mL.
• 7.2 Add 10 mL sodium hypochlorite solution to the separatory funnel, shake vigorously, then add 13%(m/m) hydrochloric acid solution 10 mL, shake vigorously for 5 min, and let stand to separate. Put the acid liquid into a 100 mL separatory funnel, then extract once more with 10 mL 13%(m/m) hydrochloric acid solution; after combining the two acid liquids, measure the absorbance E₁ according to the operating procedure in clause 6.4, and measure the absorbance E₀ of the blank test, obtaining the net absorbance E=E₁-E₀, and from E find the corresponding copper content C(μg) on the working curve.

9. Qualitative and quantitative determination and calculation formula

The copper content X(ppb) in the sample is calculated according to the following formula:

X = C × 10³ / (V × ρ)

Where:

• C — the copper content corresponding to the net absorbance of the sample on the working curve, μg;
• V — sample volume, mL;
• ρ — density of the sample at the test temperature, g/cm³.

10. Precision

Repeatability: the difference between two results of repeated determination shall not be greater than the following values:

11. Report

Take the arithmetic mean of the two results of repeated determination as the determination result.

12. Referenced documents

• GB/T 1884 Standard test method for density of crude petroleum and liquid petroleum products (hydrometer method)
• GB/T 4756 Standard practice for manual sampling of petroleum liquids

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 for questions and answers