SH/T 0605-2008 Determination of molybdenum content in lubricating oils and additives — Atomic absorption spectrometry

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Card type: Test method

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

• Standard number: SH/T 0605-2008
• Chinese full title: Determination of molybdenum content in lubricating oils and additives — Atomic absorption spectrometry
• English title: Standard test method for determination of molybdenum in lubricant and additive by atomic absorption spectrometry (AAS)
• Replacement relationship: replaces SH/T 0605—1994 "Determination of molybdenum content in lubricating oils (atomic absorption spectrometry)". SH/T 0605—1994 was formulated by equivalent adoption of DIN 51379·T3 (85) "Testing of lubricants — Determination of molybdenum content — Part 3: Atomic absorption spectrometry".
• Main changes compared with the 1994 edition (according to the foreword):
  • The scope of application is expanded; in addition to lubricating oil samples, additive samples are added;
  • Clause 5.6 was changed from "Distilled water: twice-distilled water" to "Distilled water: meets the grade-two water requirements in GB/T 6682";
  • 7.2.2 was changed from "the arithmetic mean of two absorbance values of the same solution concentration is taken as the measured value" to "the arithmetic mean of five absorbance values of the same solution concentration is taken as the measured value";
  • Clause 6.3 was changed from "blank, 5mg/L, 10mg/L, 20mg/L and 40mg/L five-point calibration" by adding two points, 30mg/L and 50mg/L, to seven-point calibration;
  • Provisions for weighing additive samples are added;
  • Repeatability and reproducibility have changed.
• Publication/implementation: published on 2008-04-23, implemented on 2008-10-01.
• Issuing body: National Development and Reform Commission of the People's Republic of China.
• Technical committee: Sinopec Research Institute of Petroleum Processing.
• Drafting organization: PetroChina Dalian Lubricant Research and Development Center.
• Participating drafting organizations: Sinopec Lubricant Chongqing Branch, PetroChina Dalian Petrochemical Branch.
• Main drafters: Lu Zebo, Li Ping, Li Li.

2. Scope of application and non-applicability

• 1.1 This standard specifies a method for determining molybdenum content in lubricating oils and additives by atomic absorption spectrometry.
• 1.2 This standard applies to molybdenum disulfide (IV) additives and to mineral oils and synthetic oils containing molybdenum disulfide (IV) additives.
• 1.3 This standard uses International System of Units [SI] units.
• 1.4 This standard involves certain hazardous materials, operations and equipment, but does not purport to address all safety problems associated with them. Therefore, users must establish appropriate safety and protective measures and determine corresponding management rules before using this standard.
• Non-applicability: no explicit non-applicability clause is provided in the available source.

3. Method principle

The sample is ashed, decomposed by heating with potassium pyrosulfate, then diluted with distilled water, and its absorbance is measured with an air/acetylene flame. The absorbance of the sample is compared with the absorbance of standard working solutions to determine the molybdenum content in the sample.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 5.1.1 Ammonium molybdate: analytical reagent.
• 5.1.2 Potassium pyrosulfate: analytical reagent.
• 5.1.3 Ammonium chloride: analytical reagent.
• 5.1.4 Aluminum chloride: analytical reagent.
• 5.1.5 Sulfuric acid: analytical reagent, prepared as a 10% (mass fraction) sulfuric acid solution.
• 5.1.6 Distilled water: meets the grade-two water requirements in GB/T 6682.

4.2 Materials

• 5.2.1 Acetylene gas: in steel cylinders, purity not lower than 99.9%. Warning: acetylene gas is flammable.
• 5.2.2 Air: compressed state (the source text here has severe source-text extraction noise, suspected to be "compressed air", requires confirmation against the source standard (source-text extraction)).

4.3 Solution preparation (preparatory work)

• 7.1 Preparation of blank solution: transfer 20g potassium pyrosulfate to a 1000mL volumetric flask, dissolve with distilled water, dilute to the mark, and mix well.
• 7.2 Preparation of molybdenum standard stock solution: weigh 1.8400g (accurate to 0.1mg) ammonium molybdate into a 250mL beaker, dissolve with distilled water, transfer to a 1000mL volumetric flask (the source text source-text extraction is "9600mL", suspected to be 1000mL, requires confirmation against the source standard (source-text extraction)), dilute to the mark with distilled water, and mix well to obtain a molybdenum standard stock solution with a molybdenum content of 1mg/mL (the source text source-text extraction is "ImeYmL", requires confirmation against the source standard (source-text extraction)).
• 7.3 Preparation of standard working solutions: accurately pipette 0.5mL, 1.0mL, 2.0mL, 3.0mL, 4.0mL and 5.0mL of the molybdenum standard stock solution into a 100mL volumetric flask, dilute to the mark with blank solution, and mix well to obtain molybdenum standard working solutions with molybdenum contents of 5mg/L, 10mg/L, 20mg/L, 30mg/L, 40mg/L and 50mg/L (the source text source-text extraction is "5ng/L", etc.; based on the context and the seven-point calibration in the foreword, it is judged to be mg/L, requires confirmation against the source standard (source-text extraction)).

5. Instruments and equipment

• 4.1 Atomic absorption spectrophotometer: wavelength range 190nm–900nm; any atomic absorption spectrophotometer capable of measuring the molybdenum analytical line (313.3nm) within the absorbance range 0.1–0.5 may be used.
• 4.2 Molybdenum hollow cathode lamp.
• 4.3 Volumetric flasks: 50mL, 100mL, 1000mL.
• 4.4 Pipettes: 0.5mL, 1mL, 2mL, 5mL (the source text source-text extraction is "ImL" "SmL", requires confirmation against the source standard (source-text extraction)).
• 4.5 Balance: sensitivity 0.1mg.
• 4.6 Beaker: 250mL.
• 4.7 High-temperature furnace: capable of maintaining a temperature of 550°C ±25°C.
• 4.8 Platinum crucible or nickel crucible: 50mL.
• 4.9 Electric heating furnace.

6. Recommended operating conditions

Table 1 Instrument reference working conditions (element Mo):

• Analytical line wavelength: 313.3 nm
• Lamp current: the source text source-text extraction has missing/garbled digits ("hand current" is suspected to be "lamp current"), requires confirmation against the source standard (source-text extraction)
• Slit: the source text source-text extraction has missing/garbled digits, requires confirmation against the source standard (source-text extraction)
• Burner height: the source text source-text extraction has missing/garbled digits, requires confirmation against the source standard (source-text extraction)
• Air flow rate: the source text source-text extraction has missing/garbled digits, requires confirmation against the source standard (source-text extraction)
• Acetylene flow rate: the source text source-text extraction has missing/garbled digits, requires confirmation against the source standard (source-text extraction)
• Extraction amount: 2.8 mL/min (the source text source-text extraction is "extraction amount mL/min 2.8", requires confirmation against the source standard (source-text extraction))
• Expansion (times): 1

Note: instrument performance differs among models; specific operations may be carried out according to the instrument manual, and the above conditions are for reference only.

7. Sampling and sample preparation

7.1 Sampling

• 6 Sampling: unless otherwise specified, sampling shall be carried out in accordance with GB/T 4756.

7.2 Preparation of sample solution

• 7.4.1 Before weighing, heat the sample to 50°C~60°C and stir thoroughly until uniform.
• 7.4.2 Weigh 2g of sample (for additive samples, weigh 1mg) into a crucible (accurate to 0.1mg), burn it as specified in GB/T 508 (the source text source-text extraction is interrupted, suspected to be "burning/ashing", requires confirmation against the source standard (source-text extraction)), then place it in a 550°C±25°C high-temperature furnace for ashing treatment.
• 7.4.3 After the residue has cooled, add 1g potassium pyrosulfate to the crucible and place it on an electric furnace, heating until a clear melt forms.
• 7.4.4 After cooling, pour hot distilled water into the crucible, heat slightly, and stir with a glass rod to dissolve it. Quantitatively transfer the clear solution to a 50mL volumetric flask, dilute to the mark with distilled water, and mix well.
• 7.4.5 If turbidity appears while the melt is dissolving, add some sulfuric acid solution to clarify it, then quantitatively transfer the clear solution to a 50mL volumetric flask, dilute to the mark with distilled water, and mix well; add equal amounts of sulfuric acid solution to the blank solution and the standard working solutions.
• 7.4.6 If the sample contains interfering ions such as calcium and iron, add 1g ammonium chloride and 0.25g aluminum chloride to the sample solution. After dissolution, quantitatively transfer the clear solution to a 50mL volumetric flask, dilute to the mark with distilled water, and mix well.

8. Analytical procedure

• 8.1 Adjust the instrument according to the conditions in Table 1.
• 8.2 Measure absorbance
  • 8.2.1 Zero the instrument with the blank solution.
  • 8.2.2 Measure the absorbance of the molybdenum standard working solutions, first from low to high solution concentration, then from high to low; take the arithmetic mean of five absorbance values of the same solution concentration as the measured value, and plot the standard working curve of molybdenum standard working solution concentration versus absorbance.
  • 8.2.3 Zero the instrument with the blank solution.
  • 8.2.4 Measure the absorbance of the sample solution.
  • 8.2.5 Measure the absorbance of the standard working solution whose absorbance is closest to that of the sample solution.
  • 8.2.6 Repeat steps 8.2.3~8.2.5, and take the arithmetic mean of the two absorbance values as the measured value.
  • 8.2.7 The standard working solutions and the sample solution shall be measured at the same time, and their absorbance shall be measured on the same day.

9. Qualitative and quantitative determination and calculation formula

Calculate the molybdenum content X, % (mass fraction) in the sample using formula (1):

X = (Ax × C × V) / (As × m × 10⁶) × 100 ………………(1)

Where:

• Ax— average absorbance of the sample solution;
• As— average absorbance of the standard working solution closest to the sample solution;
• C— concentration of the standard working solution corresponding to As, mg/L;
• V— volume of the sample, mL;
• m— mass of the sample, g.

Note 1: The above formula applies only when the standard working curve of molybdenum standard working solution concentration versus absorbance is a straight line. After the sample solution is diluted, the dilution factor must be determined in the calculation. Note 2: The standard working curve of molybdenum standard working solution concentration versus absorbance can also be drawn by the instrument's computer and the test results can be obtained directly.

10. Precision

Judge the reliability of the determination results according to the following provisions (95% confidence level).

10.1 Repeatability

The difference between two consecutive results obtained by the same operator using the same instrument under the same operating conditions on the same test sample for repeated determinations shall not exceed the value of formula (2).

r = 0.1X ……………… (2)

Where: X— the arithmetic mean of the two test results of repeated determinations.

10.2 Reproducibility R

The difference between two independent test results obtained by different operators using different instruments under the same operating conditions on the same test sample shall not exceed the value of formula (3).

R = 0.3X ……………… (3)

Where: X— the arithmetic mean of the two independent test results.

11. Report

Take the arithmetic mean of the two results of repeated determinations as the determination result, rounded to three decimal places.

12. Normative references

• GB/T 508 Petroleum products—Determination of ash (GB/T 508—1985, ref ISO 6245:1982)
• GB/T 4756 Petroleum liquids—Manual sampling (GB/T 4756—1998, eqv ISO 3710:1988) (the source text source-text extraction is “CB/T 4756”, requires confirmation against the source standard (source-text extraction))
• GB/T 6682 Water for analytical laboratory use—Specification and test methods (GB/T 6682—1992, neq ISO 3696:1987) (the source text source-text extraction is “CB/T 6682”, requires confirmation against the source standard (source-text extraction))

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