SH/T 0706-2001 Determination of aluminum and silicon content in fuel oil (inductively coupled plasma emission spectrometry and atomic absorption spectrometry)

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Card type: Test method

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

• Standard number: SH/T 0706-2001
• Chinese full name: Determination of aluminum and silicon content in fuel oil (inductively coupled plasma emission spectrometry and atomic absorption spectrometry)
• English name: Petroleum products-Determination of aluminium and silicon in fuel oils-Inductively coupled plasma emission and atomic absorption spectroscopy methods
• Replacement relationship: not provided in the available source (the foreword only states equivalent adoption of ISO 10478:1994, and does not mention replacing any old standard)
• Adoption relationship: eqv ISO 10478:1994
• Publication/implementation: published on 2001-11-23, implemented on 2002-01-01
• Publishing unit: State Economic and Trade Commission
• Responsible unit: Sinopec Research Institute of Petroleum Processing
• Drafting unit: Fushun Petroleum Institute
• Main drafters: Ma Bo, Li Ping, Zhao Shanlin, Yao Lizhu

2. Scope of application and non-applicability

• Applicable to the determination of aluminum and silicon content in fuel oil.
• Aluminum content range: 5 mg/kg～150 mg/kg.
• Silicon content range: 10 mg/kg～250 mg/kg.
• Not applicable: not provided in the available source.

3. Method principle

Take a certain amount of uniformly mixed sample in a platinum crucible, heat to carbonize the sample, then place it in a high-temperature furnace at 550℃±25℃ and heat to ash. The residue is melted with dilithium tetraborate and lithium fluoride, then digested with tartaric acid-hydrochloric acid solution, and finally diluted with water to a certain volume. Then introduce the test solution into the inductively coupled plasma emission torch, measure the emission light of the aluminum/silicon resonance line, and compare it with the emission light of the standard solution; or introduce the test solution into the flame of an atomic absorption spectrometer, measure the absorption of the aluminum/silicon resonance line, and compare it with the absorption of the resonance line of the standard solution.

4. Reagents and materials (purity / preparation)

All reagents used are analytical grade, and water shall meet the grade 2 water requirements of GB/T 6682.

• 4.1 Potassium bisulfate (KHSO₄): solid.
• 4.2 Flux: a mixture of 90%(m/m) dilithium tetraborate (Li₂B₄O₇) and 10%(m/m) lithium fluoride (LiF).
• 4.3 Isopropanol.
• 4.4 Toluene.
• 4.5 Toluene-isopropanol mixture (1+1): mix one volume of isopropanol with one volume of toluene.
• 4.6 Hydrochloric acid: concentration is 36%(m/m).
  • 4.6.1 Hydrochloric acid solution (1+1): mix one volume of hydrochloric acid with one volume of water.
  • 4.6.2 Hydrochloric acid solution (1+2): mix one volume of hydrochloric acid with two volumes of water.
• 4.7 Tartaric acid.
  • 4.7.1 Tartaric acid-hydrochloric acid mixed solution: dissolve 5 g (accurate to 0.1 g) of tartaric acid in about 500 mL of water acidified with 40 mL hydrochloric acid (4.6), and dilute with water to 1000 mL.
• 4.8 Standard solutions
  • 4.8.1 Aluminum standard solution: a commercially available 1000 mg/L aluminum standard solution may be used, or in a 400 mL beaker, dissolve 1.000 g (accurate to 0.0001 g) of aluminum metal wire (purity 99.99%) with 50 mL hydrochloric acid (4.6) under gentle heating. After cooling, transfer to a 1000 mL volumetric flask, dilute to the mark with water to obtain a 1000 mg/L aluminum standard solution. When in use, take 25 mL aluminum standard solution and dilute to 100 mL to prepare a 250 mg/L aluminum working solution.
  • 4.8.2 Silicon standard solution: a commercially available 1000 mg/L silicon standard solution may be used, or place 2.140 g (accurate to 0.0001 g) of silicon dioxide with purity 99.99% and 8 g sodium hydroxide in a platinum crucible with a sealed cover and heat (control the electric furnace wire to a dark red color) until the melt becomes a clear liquid. After cooling, in a 400 mL beaker, dissolve the solidified melt with 100 mL hydrochloric acid solution (4.6.2), after cooling transfer to a 1000 mL volumetric flask, dilute to the mark with water, then immediately transfer to a 1000 mL plastic bottle for long-term storage to obtain a 1000 mg/L silicon standard solution. When in use, take 25 mL silicon standard solution and dilute to 100 mL to prepare a 250 mg/L silicon working solution.

5. Instruments and equipment

• 5.1 Platinum crucible: capacity 100 mL, cleaned with potassium bisulfate.
  • Note: Recommended cleaning technique—place 5 g potassium bisulfate in a platinum crucible, heat in a high-temperature furnace to 550℃±25℃ or heat on an electric furnace for 5 min. After cooling, wash with distilled water or deionized water and dry.
• 5.2 Platinum crucible: with sealed cover, capacity 30 mL～50 mL.
• 5.3 Stirrer: non-aerating, high-speed shear type.
• 5.4 Electric furnace: temperature control 50℃～60℃.
• 5.5 Electric high-temperature furnace: can maintain temperatures 550℃±25℃ and 925℃±25℃, preferably with some small holes on the front and back of the furnace so that dry air can pass slowly through.
• 5.6 Electric hot plate: with or without magnetic stirring function.
• 5.7 Spectrometer
  • 5.7.1 Inductively coupled plasma emission spectrometer (ICP): use a sequential or simultaneous determination spectrometer, equipped with a ICP torch and a high-frequency (RF) generator, capable of forming a sustained plasma.
  • 5.7.2 Atomic absorption spectrometer: with an adjustable hollow cathode lamp or a light source capable of radiating aluminum and silicon; with a nitrous oxide-acetylene atomizer; with a light detector with a suitable measurement and readout system. The scale should be linear with respect to light absorption or light intensity, or directly expressed in concentration units after curve correction.
• 5.8 Volumetric flasks: 100 mL, 1000 mL.
• 5.9 Pipettes: 1 mL, 2 mL, 5 mL, 10 mL, 20 mL and 25 mL.
• 5.10 Pipettes: 1 mL, 2 mL, graduation value 0.1 mL.
• 5.11 Graduated cylinders: 10 mL, 25 mL, 50 mL and 100 mL.
• 5.12 Beakers: 400 mL flat-bottomed beakers.
• 5.13 Filter paper: ashless filter paper with a maximum ash content of 0.01%(m/m).
• 5.14 Plastic bottles: new plastic bottles suitable for long-term storage of dilute acid solutions, capacities 100 mL and 1000 mL.
• 5.15 Analytical balance: sensitivity 0.2 mg.

6. Recommended operating conditions

• ICP Excitation source: before analysis, it should be stabilized for more than 30 min, and during the warm-up period, introduce distilled water or deionized water into the plasma torch. Note: Some manufacturers may recommend a longer warm-up time.
• Peristaltic pump: if used, check the pump tubing before starting each day to see whether it needs replacement; verify the extraction rate of the calibration solution and adjust it to an appropriate value.
• Operating parameters (ICP): element, wavelength, number of background correction points, number of internal standard element correction points, integration time, and three consecutive replicate integrations.
• Instrument settings for determination of aluminum by atomic absorption method (Table 1): wavelength 309.3 nm; fuel gas acetylene; oxidant nitrous oxide; lamp current as recommended by the manufacturer, generally 60%～100% of the maximum value.
• Instrument settings for determination of silicon by atomic absorption method (Table 2): wavelength 251.6 nm; fuel gas acetylene; oxidant nitrous oxide; lamp current as recommended by the manufacturer.
• Adjustment for aluminum determination by atomic absorption method: aspirate aluminum standard calibration solution (25 mg/L) into the flame, adjust the burner height, correct the burner, acetylene flow rate, and impact bead to obtain maximum absorption (or minimum transmittance); adjust the gain so that the maximum value is obtained within the range recommended by the spectrometer (see instrument manual).
• Determination of silicon by atomic absorption method: install the silicon hollow cathode lamp, set the monochromator to the specified wavelength (Table 2), adjust the wavelength to obtain maximum output; the following operating steps are the same as 7.6.2, aspirate silicon standard calibration solution (25 mg/L) into the flame.

7. Sampling and sample preparation

• Before sampling, the sample should be mixed uniformly. Place the sample container on an electric furnace at a temperature of 50℃～60℃ until the sample is completely melted and reaches a uniform viscosity.
• Then insert the stirrer (5.3) rod into the sample; the insertion depth of the stirring rod should be such that the rod head is 5 mm from the bottom of the container, and stir the sample for 5 min.
• If the liquid sample has been left standing for several months, before stirring the sample, first stir up the sediment deposited at the bottom of the container with a stirring rod.
• Note: If the sample is not homogenized according to this procedure, the results obtained will be invalid.
• Sampling amount: weigh 20 g～50 g of sample from the homogenized sample, preferably containing about 1.3 mg of aluminum.
• Note: The recommended sampling amount is based on consideration of aluminum content; due to the correlation between silicon and aluminum in fuel oil, it should also be sufficient for the determination of silicon.

8. Analytical procedure

7.2 Preparation of sample solution

• 7.2.1 After taking the sample from the homogenized sample, transfer it to a weighed platinum crucible, then weigh again, accurate to 0.1 g, and calculate the mass of the sample taken.
• 7.2.2 Heat the platinum crucible containing the sample slowly with an electric furnace until the sample ignites. Maintain the heating temperature so that all combustible components in the sample are burned off, leaving only carbon and ash.
  • Note: If the sample contains a large amount of water, bubbling during combustion will cause loss of sample. If bubbling occurs, the sample should be discarded and a new sample taken, and after adding 1 mL～2 mL of isopropanol to the new sample, heat it. If the bubbling still does not disappear, add 10 mL of toluene-isopropanol mixture to the sample and mix uniformly, place some strips of ashless filter paper in the mixture, heat gently, and as the paper strips burn, the water will be removed.
• 7.2.3 Place the combusted platinum crucible into a 550℃±25℃ high-temperature furnace, maintain this temperature until all carbon is burned off, leaving only ash.
  • Note: This step may require ashing overnight.
• 7.2.4 Remove the platinum crucible and cool to room temperature, add 0.4 g flux to the platinum crucible and mix with the ash. Then place the platinum crucible into a high-temperature furnace preheated to 925℃±25℃ for 5 min, remove it, ensure the flux and ash are fully contacted, place the platinum crucible back into the high-temperature furnace, and burn again at 925℃±25℃ furnace temperature for 10 min.
• 7.2.5 Remove the platinum crucible, wait for the sample to cool to room temperature, add 50 mL tartaric acid-hydrochloric acid mixed solution, place the platinum crucible on a hot plate, and heat gently without boiling until the melt is completely dissolved.
  • Note1: Excessive evaporation of the solution may form a sparingly soluble form of silica precipitate.
  • Note2: In order to completely dissolve the melt, the heating time needs to be extended; a magnetic stirrer or shaking method can be used to accelerate the dissolution process.
• 7.2.6 After the solution cools, transfer it to a 100 mL volumetric flask, rinse the platinum crucible several times with water, then add water to the volumetric flask to dilute to the mark, and transfer to a 100 mL plastic bottle.
  • Note: Because the dilute acid solution contains tetrafluoroboric acid (from the flux), the solution should be transferred to a plastic bottle. However, storage experiments show that within one week there is no corrosive effect on glassware, and the concentration of free fluoride ions contained in the solution is less than 5 mg/L.

7.3 Preparation of blank solution

In a 100 mL volumetric flask, add 0.4 g flux and 50 mL tartaric acid-hydrochloric acid mixed solution, dilute with water to 100 mL, then transfer to a 100 mL plastic bottle.

7.4 Preparation of standard calibration solutions

• 7.4.1 Aluminum standard calibration solutions: In four 100 mL volumetric flasks, respectively add 0.4 g flux and 50 mL tartaric acid-hydrochloric acid mixed solution, then respectively add 2 mL, 4 mL, 10 mL and 20 mL of 250 mg/L aluminum working solution, dilute with water to the mark. The aluminum concentrations of the four standard calibration solutions are respectively 5 mg/L, 10 mg/L, 25 mg/L and 50 mg/L.
• 7.4.2 Silicon standard calibration solutions: In four 100 mL volumetric flasks, respectively add 0.4 g flux and 50 mL tartaric acid-hydrochloric acid mixed solution, then respectively add 2 mL, 4 mL, 10 mL and 20 mL of 250 mg/L silicon working solution, dilute with water to the mark. The silicon concentrations of the four standard calibration solutions are respectively 5 mg/L, 10 mg/L, 25 mg/L and 50 mg/L.
• 7.4.3 Storage: Transfer all standard calibration solutions to 100 mL plastic bottles.
  • Note: When aluminum and silicon are determined simultaneously, if the reagents used for the standard solutions prepared in 4.8.1 and 4.8.2 do not match, then each aluminum and silicon standard calibration solution from 5 mg/L to 50 mg/L may be combined for use.

7.5 Determination of aluminum and silicon by inductively coupled plasma emission spectrometry

• 7.5.1 General: Operate the instrument according to the instrument manual. Select parameters according to the instrument used.
  • Note: Due to differences among instruments in design, ICP excitation source, and selected analytical wavelengths, it is difficult to specify the required operating conditions in detail.
• 7.5.2 Peristaltic pump: If a peristaltic pump is used, check the pump tubing before starting up each day to see whether it needs replacement. Verify the extraction rate of the calibration solution and adjust it to an appropriate value.
• 7.5.3 ICP excitation source: Before analysis, the ICP excitation source should be stabilized for more than 30 min; during this warm-up period, introduce distilled water or deionized water into the plasma torch.
  • Note: Some manufacturers may recommend a longer warm-up time.
• 7.5.4 Under normal instrument operating conditions, determine the spectra of the elements to be measured as required.
• 7.5.5 Operating parameters: In order to determine the required elements, appropriate operating parameters need to be set for the instrument, mainly including: element, wavelength, number of background correction points, number of internal standard element correction points, integration time, and three consecutive replicate integrations.
• 7.5.6 Calibration curve: Before starting the analysis of each batch of samples, use the blank solution and standard calibration solutions to perform a five-point calibration and draw the curve.
• 7.5.7 Analyze the samples according to the analysis conditions of the standard calibration solutions. After each sample analysis, spray distilled water or deionized water to rinse the torch for at least 10 s. If the concentration of the sample solution is found to exceed the concentration range of the standard calibration solutions, dilute with the blank solution so that the concentration of the sample solution is within the concentration range of the standard calibration solutions. After every five samples analyzed, calibrate once with a standard calibration solution (any one); if the concentration of a certain element is found to exceed 5% of the known value, necessary adjustments to the instrument and recalibration are required.

7.6 Determination of aluminum and silicon by atomic absorption spectrometry

• 7.6.1 General: Operate the instrument according to the instrument operating manual.
  • Note: Due to differences in instrument design, it is impossible to require special operating conditions.
  • Caution: For safety and to obtain reliable results, operate the instrument according to correct operating procedures; the correct burner head and operating steps must be used, otherwise flashback may occur and lead to explosion.
• 7.6.2 Determination of aluminum: Install the aluminum hollow cathode lamp, adjust the monochromator to a suitable wavelength (see Table 1), and adjust the wavelength to obtain maximum output; aspirate the aluminum standard calibration solution (25 mg/L) into the flame. Adjust the burner height, calibrate the burner, acetylene flow rate, and impact bead to obtain maximum absorption (or minimum transmittance). Adjust the gain so that it obtains the maximum value within the range recommended by the spectrometer (see instrument manual).
• 7.6.3 Determination of silicon: Install the silicon hollow cathode lamp, adjust the monochromator to the specified wavelength (see Table 2), and adjust the wavelength to obtain maximum output. The following operating steps are the same as 7.6.2; aspirate the silicon standard calibration solution (25 mg/L) into the flame.
• 7.6.4 Calibration curve: Before each group of samples is analyzed and after instrument conditions are changed, a calibration curve must first be made. Because some changes will occur in the instrument state. The type of readout device of the atomic absorption spectrometer determines the calibration method.
  • Note: If scale deposits in the burner slit or nebulizer, it can cause the reading to change within a short time. Observing the appearance of the flame is very useful for checking changes in measurement conditions.
• 7.6.5 Analysis of sample solutions
  • 7.6.5.1 General: After every five samples, calibrate once with a standard calibration solution; if the analysis results show that the concentration value of the calibration solution has changed (see 7.6.4), recalibrate the instrument. If the sample concentration is found to exceed the concentration range of the standard calibration solutions, dilute with the blank solution so that the sample solution concentration returns to the concentration range of the calibration solutions.
  • 7.6.5.2 Spectrometers using meter readings: Aspirate the calibration solution, blank solution, and sample solution into the flame in sequence, record the meter readings, and aspirate the blank solution before each sample solution. If the absorbance output of the spectrometer is linear, plot a curve of net absorbance (absorbance of the standard solution minus absorbance of the blank solution) versus concentration. After calculating the net absorbance for each sample solution, its concentration can be calculated from this curve. If the output of the spectrometer is proportional to transmittance (i.e., light intensity), use formula (1) to calculate the net absorbance A:
    • A = lg(d₀/d₁)
    • Where: d₀—meter reading of the blank solution; d₁—meter reading of the standard calibration solution or sample solution.
  • 7.6.5.3 Spectrometers equipped with direct reading and built-in (microprocessor-controlled) curve correction and scale expansion equipment: According to the instrument operating manual, aspirate an appropriate amount of standard calibration solution, adjust the digital readout system so that the displayed number is directly in the required concentration units, and if necessary, perform curve correction. Aspirate the sample solution and read the concentration values of each sample solution and blank solution directly displayed digitally on the spectrometer.
  • 7.6.5.4 Spectrometers equipped with a digital readout microprocessor-controlled calibration accessory: According to the instrument operating manual, aspirate an appropriate amount of standard calibration solution and use the recommended calibration program so that it is directly displayed in concentration units. In this way, the concentration of each sample solution and blank solution can be obtained directly after aspirating the solution.

9. Qualitative and quantitative determination and calculation formulas

Use formula (2) and formula (3) to respectively calculate the aluminum content X_Al (mg/kg) and silicon content X_Si (mg/kg) of the sample:

• X_Al = 100 c₁ d / m ………………(2)
• X_Si = 100 c₂ d / m ………………(3)

Where:

• c₁—concentration of aluminum in the sample solution (mg/L); this reading can be read from the inductively coupled plasma emission spectrometry readout system or calibration curve, or directly from the atomic absorption spectrometer;
• c₂—concentration of silicon in the sample solution (mg/L); this reading can be read from the inductively coupled plasma emission spectrometry readout system or calibration curve, or directly from the atomic absorption spectrometer;
• d— dilution factor, the volume multiple by which the sample solution needs to be diluted so that its concentration falls within the concentration range of the calibration solutions; when the dilution procedure of 7.5.7 or 7.6.5.1 has not been performed, d=1;
• m— mass of the sample weighed, g.

Expression of results: Whether using an inductively coupled plasma emission spectrometer or an atomic absorption spectrometer, the measured aluminum content and silicon content are accurate to 1 mg/kg.

10. Precision

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

10.1 Inductively coupled plasma emission spectrometry

• 10.1.1 Repeatability (r): the same operator using the same instrument, on the same test sample, the difference between two results obtained shall not exceed the value of formula (4) or formula (5).
  • r_Al = 0.0660X ………………(4)
  • r_Si = 0.0643X ………………(5)
  • Where: X— arithmetic mean of the two results of repeated determinations, mg/kg.
• 10.1.2 Reproducibility (R): different operators in different laboratories, using different instruments on the same test sample, the difference between two results obtained shall not exceed the value of formula (6) or formula (7).
  • R_Al = 0.337X ………………(6) (requires confirmation against the source standard (source-text extraction): the formula coefficient source-text extraction in the source text is shown as "337X", suspected to be 0.337X)
  • R_Si = 0.332X ………………(7) (requires confirmation against the source standard (source-text extraction): the formula coefficient source-text extraction in the source text is shown as "332A", suspected to be 0.332X)
  • Where: X— arithmetic mean of the two results proposed by different laboratories, mg/kg.

10.2 Atomic Absorption Spectrometry

• 10.2.1 Repeatability (r): the same operator using the same instrument, on the same test sample, the difference between two results obtained shall not exceed the value of formula (8) or formula (9).
  • r_Al = 0.2968X^(2/3) ………………(8) (the source equation is garbled; the exponent interpreted as 2/3 remains unverified and must be checked before use)
  • r_Si = 0.3539X^(1/3) ………………(9) (requires confirmation against the source standard (source-text extraction): the source text shows "r3 4!=0.3539X'/3", the exponent is suspected to be 1/3)
  • Where: X— arithmetic mean of the two results of repeated determinations, mg/kg.
• 10.2.2 Reproducibility (R): different operators in different laboratories, using different instruments on the same test sample, the difference between two results obtained shall not exceed the value of formula (10) or formula (11).
  • R_Al = 0.7890X^(1/3) ………………(10) (requires confirmation against the source standard (source-text extraction): the source text shows "RM=0.7890X"3", the exponent is suspected to be 1/3)
  • R_Si = 1.388X^(1/3) ………………(11) (requires confirmation against the source standard (source-text extraction): the source text shows "Rf j=1.388X'", the exponent is suspected to be 1/3)
  • Where: X— arithmetic mean of the two results proposed by different laboratories, mg/kg.

11. Report

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

12. Referenced Documents

• GB/T 6682 Specifications and test methods for water for analytical laboratory use
• ISO 10478:1994 Petroleum products—Determination of aluminum and silicon in fuel oils—Inductively coupled plasma emission spectrometry and atomic absorption spectrometry (equivalent adoption)

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