NB/SH/T 0892-2015 Determination of trace elements in middle distillate fuels by inductively coupled plasma atomic emission spectrometry

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Card type: Test method

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

• Standard number: NB/SH/T 0892—2015 (the cover also has source-text extraction noise written as NB/SHVT 0892—2015, requires confirmation against the source standard (source-text extraction))
• Chinese title: Determination of trace elements in middle distillate fuels by inductively coupled plasma atomic emission spectrometry
• English title: Standard test method for determination of trace elements in middle distillate fuels by inductively coupled plasma atomic emission spectrometry (ICP-AES) (the original "clements" is source-text extraction noise, requires confirmation against the source standard (source-text extraction)))
• Replacement relationship: This standard is first published; it uses the redrafting method to modify and adopt ASTM D7111-11
• Main technical differences from ASTM D7111-11:
  • Deleted the content concerning the International System of Units in clause ASTM D7111-11 1.4
  • In Chapter 2 "Normative references", some are replaced by corresponding national standards of our country
  • Changed Chapter 5 "Significance and use" to "Method application"
  • Deleted the keywords of Chapter 20
• Publication/implementation: published on 2015-10-27, implemented on 2016-03-01
• Issuing authority: National Energy Administration
• Drafting organization: Sinopec Research Institute of Petroleum Processing
• Main drafters: Gao Ping, He Jing, Mao Xinye

2. Scope of application and non-applicability

• Applicable to the determination of some elements in middle distillate fuels by ICP-AES (see Table 1)
• Applicable determination element content range: mass fraction approximately 0.1 mg/kg ~ 2.0 mg/kg; samples outside this range may be determined by referring to the test procedure of this standard, but the precision may not be applicable
• Definition of middle distillate fuels: all fractions with a boiling point range of 150 ℃ ~ 390 ℃, including but not limited to diesel and jet fuel
• Not applicable: This standard is not intended for the analysis of insoluble particulate matter; however, very fine particulate matter (smaller than 1 μm) will be introduced into the plasma and quantitatively analyzed
• Bias note: If an element to be determined in the sample exists in a volatile form, the determination result will be higher than the true value (for example, when determining a sample containing hexamethyldisiloxane, the determination of silicon will produce a bias, making the result higher)

3. Method principle

Prepare calibration standard solutions by mixing organometallic standard samples with kerosene. An internal standard shall be added to the calibration standard solutions and fuel samples. Aspirate the calibration standard solutions and fuel samples into the ICP-AES spectrometer. By comparing the element emission intensities in the fuel sample and the calibration standard solutions, the content of elements in the fuel sample is calculated after internal standard correction.

4. Reagents and materials (purity / preparation)

• 4.1 Reagent purity: All chemical reagents used in the test are of analytical grade; if reagents of other grades are used, it must be ensured that they are of sufficient purity and will not reduce the detection accuracy after use
• 4.2 Internal standard: yttrium, cobalt, scandium, etc., or other organometallic standard substances soluble in fuel, generally with a mass fraction of 5000 mg/kg; the internal standard element should be an element not present in the fuel sample and calibration standard solutions
• 4.3 Kerosene diluent: The content of the elements to be determined should be lower than the method detection limit; the elements to be determined contained in the diluent may be detected by wavelength scanning as described in clause 12.1
• 4.4 Argon: purity (mass fraction) not less than 99.995% (Warning: high-pressure gas)
• 4.5 Nitrogen: purity (mass fraction) not less than 99.999% (Warning: high-pressure gas)
• 4.6 Oxygen: purity (mass fraction) not less than 99.999% (Warning: high-pressure gas)
• 4.7 Nitric acid: aqueous solution with a volume fraction of 10% (Warning: nitric acid can cause serious injury)
• 4.8 Quality control (QC) samples: Select one or more fuel or kerosene samples that can represent the characteristics of the samples to be tested and are stable as the QC samples; check the effectiveness of the test process according to Chapter 18; if no suitable fuel sample is available, a stable QC concentrated solution may also be selected, and on the day of the QC test, dilute with kerosene to the concentration range in clause 12.3; HDPE plastic bottles should be used to contain the QC concentrated solution, and HDPE plastic bottles should also be used when performing sodium element analysis

Preparation of internal standard stock solution (12.2)

• The selection of a single-element internal standard varies depending on the instrument's detection capability (wavelength applicability and sensitivity); the single element selected as the internal standard should be an element not present in the fuel and calibration standard solutions
• Prepare the internal standard stock solution using a single-element internal standard solution with a mass fraction of 5000 mg/kg and kerosene diluent; the prepared concentration is approximately 50 times the content of the element to be determined in the fuel or the element content in the working standard solution; prepare at least 50 g; the shelf life is one week
• Example (yttrium internal standard stock solution with mass fraction 50 mg/kg): Weigh 0.5 g (accurate to 0.001 g) of a yttrium organometallic internal standard solution with a mass fraction of 5000 mg/kg, add kerosene diluent to 50.0 g (accurate to 0.001 g), cap the container and mix thoroughly

Preparation of working standard solution (12.3)

• Take the preparation of a working standard solution with a mass fraction of 2.0 mg/kg as an example; the concentration may be slightly higher or lower, determined according to the sensitivity of the ICP spectrometer and the emission intensity of the element to be determined in the fuel sample
• Determine the appropriate working standard solution concentration based on the element emission intensity in a kerosene sample with a known element content (e.g., mass fraction 1.0 mg/kg); when the working standard solution is determined, its measured value is acceptable within the 5% error range
• Commercially available organic standard substances with certified element contents may also be used
• Preparation of calibration standard solution with mass fraction 2.0 mg/kg: Weigh 1.0 g (accurate to 0.0001 g) of 100 mg/kg organometallic standard substance (containing all metals to be determined), add kerosene diluent to 50.0 g, cap the container and mix thoroughly, calculate the element content according to clause 16.1; it should be prepared on the day of sample analysis
• Preparation of working standard solution: Pipette 1000 μL of internal standard stock solution into a 50 mL volumetric flask, add the calibration standard solution prepared in 12.3.2 and dilute to the mark, cap the bottle and mix thoroughly; it should be prepared on the day of sample analysis
• If the working standard solution is prepared using the yttrium internal standard stock solution in A2.2.3, the mass fraction of the internal standard element in the solution is 1.0 mg/kg

Instrument check standard solution (12.4)

Prepare the instrument check standard solution in the same way as the working standard solution (see clause 12.3), and its concentration should be close to that of the fuel sample; other organic standard substances with accurate concentrations may be used to prepare the check standard solution.

Sample preparation (12.5)

Add 1000 μL of internal standard stock solution to a 50 mL volumetric flask, and dilute to the mark with the fuel sample; the concentration of the internal standard stock solution added should be the same as that used in preparing the working standard solution; if the amount of fuel sample is insufficient, a smaller volumetric flask may be used and the volume of internal standard stock solution added reduced accordingly; because the amount of internal standard stock solution added to the working standard and fuel sample is the same, no dilution factor correction is required.

5. Instruments and equipment

• 5.1 Inductively coupled plasma atomic emission spectrometer: any commercial sequential or simultaneous full-spectrum direct-reading ICP-AES spectrometer may be used for element determination (elements see Table 1); when the wavelength of the element spectral line to be determined is less than 190 nm, a vacuum system or inert gas purge of the optical path is required
• 5.2 Nebulizer: A high-salt nebulizer is recommended to reduce particle blockage
• 5.3 Spray chamber: Suitable for organic materials
• 5.4 Peristaltic pump: Can provide a stable liquid flow rate for the ICP-AES spectrometer; the pump tubing should be resistant to fuel oil and kerosene
• 5.5 Filter membrane (optional): diameter 47 mm, pore size 0.8 μm or 1.0 μm, made of nylon, polytetrafluoroethylene, cellulose acetate/cellulose nitrate or other similar materials
• 5.6 Filter membrane holder assembly (optional): with a volumetric flask that can hold the filtrate, can install a 47 mm filter membrane
• 5.7 Pipette: 1000 μL
• 5.8 Volumetric flask: 25 mL and 50 mL glass volumetric flasks
• 5.9 Glass bottle or high-density polyethylene (HDPE) bottle: round, 125 mL
• 5.10 Balance: readability 0.0001 g

6. Recommended operating conditions

• Elements to be determined and recommended spectral line wavelengths (Table 1):

• Internal standard elements and recommended wavelengths and mass fractions (Table 2):

(Note: the mass fraction corresponding to cobalt in Table 2 is not provided in the available source; for yttrium, two rows correspond to wavelength and mass fraction, and source-text extraction may be misaligned, requires confirmation against the source standard (source-text extraction))

• 6.1 concentration range: specific values are not provided in the available source (the content of this section is missing from the source text)
• 6.2 if spectral interference exists, wavelengths other than those in Table 1 and Table 2 may also be selected; the newly selected wavelength should have suitable sensitivity within the applicable range of the method
• 6.3 if interference cannot be eliminated through wavelength selection and background correction, software correction provided by the instrument manufacturer may be used; see Chapter 6 in GB/T 17476—1998 for empirical methods of spectral correction
• All test samples (standard samples, blanks and fuels) shall be subjected to at least three integration measurements
• The optical system may be purged with argon or other high-purity gas (such as nitrogen) according to the conditions recommended by the instrument manufacturer
• Before plasma ignition, check whether the quartz torch tube is clean; if carbon deposits are observed, the quartz tube should be replaced and handled according to the method recommended by the instrument manufacturer
• Preheat the instrument while purging the optical path according to the conditions recommended by the instrument manufacturer; if the peristaltic pump tubing needs to be replaced and the sample introduction rate adjusted; ignite the torch tube, aspirate kerosene, and continue instrument preheating and stabilization for the time specified by the manufacturer of the ICP spectrometer

7. Sampling and Sample Preparation

• 7.1 Sampling shall be carried out in accordance with GB/T 4756 or other equivalent methods; when sodium element needs to be analyzed, use high-density polyethylene (HDPE) plastic bottles
• 7.2 Samples shall be thoroughly mixed in the container before measurement
• 7.3 If particulate matter can be observed in the sample, filter it through a membrane with a pore size of 0.8 μm to 1.0 μm into an acid-washed clean narrow-mouth bottle, then analyze the filtered sample; when analyzing such samples, the kerosene diluent shall also undergo the same filtration treatment
• 7.4 Glassware and plasticware: clean glassware and plasticware with nitric acid at a volume fraction of 10%, then rinse with deionized water; do not use glassware or plasticware containing relatively high levels of the elements to be determined

8. Analytical Procedure

8.1 Instrument Preparation (Chapter 11)

Set the operating conditions for organic samples and select the elements to be determined according to the operating instructions of the ICP spectrometer manufacturer; all test samples (standard samples, blanks and fuels) shall be subjected to at least three integration measurements; Table 1 provides the recommended element wavelengths; because spectral interference effects differ among different spectrometers, not all usable wavelengths are listed in Table 1; the optical system may be purged with argon or other high-purity gas (such as nitrogen) according to the conditions recommended by the instrument manufacturer; before plasma ignition, check whether the quartz torch tube is clean; if carbon deposits are observed, the quartz tube should be replaced and handled according to the method recommended by the instrument manufacturer; preheat the instrument while purging the optical path according to the conditions recommended by the instrument manufacturer; if necessary, replace the peristaltic pump tubing and adjust the sample introduction rate; ignite the torch tube, aspirate kerosene, and continue instrument preheating and stabilization for the time specified by the manufacturer of the ICP spectrometer.

8.2 Wavelength and Background Correction (Chapter 13)

• The recommended wavelengths for the elements to be determined and the internal standard element are listed in Table 1 and Table 2 respectively
• Because ICP instruments differ in type and performance, some of the most commonly used spectral lines in the tables may also be used; spectral lines shall be selected based on the principles of optimal emission intensity, peak shape and absence of interference for the element
• Because trace elements are being determined, background correction is required; for all elements determined, the baseline background (BK) point of the emission spectral peak shall be close to positions on both sides of the peak shape where there is emission intensity signal (see Figure 1); after the baseline background is set, retest the standard solution and calibrate using the method described in the next section
• 13.2 When determining sodium, selecting an appropriate wavelength and background correction is very important, because the main emission lines of sodium (588.995 nm) have strong argon emission line interference; during method development, the sample spectra and standard calibration sample spectra should be compared on the emission lines as much as possible to ensure correct integration signals
• Note: Some emission spectral peaks may occur at relatively high baseline background positions (for example, sodium 588.995 nm), so using a single peak background correction point may cause erroneous results; for such emission lines at relatively high baseline background, background correction is recommended to use a two-point correction method with one lower point and one higher point; low-resolution instruments or instruments using photomultiplier tubes as detectors may give incorrect results because they provide a combined background formed by spectral line overlap

8.3 Calibration (Chapter 14)

• 14.1 Within the linear range of the instrument, perform two-point calibration using kerosene diluent and working standard solutions; this shall be done each time a new batch of fuel samples is analyzed

• 14.2 Determine through measurement of check standard solutions that the calibration is applicable to all elements to be determined; only when the error of each element from the theoretical value is less than 5% may fuel samples be measured; otherwise, the instrument must be adjusted and recalibrated until the element deviation in the check standard solution is less than 5%

• 14.3 Before measuring standard solutions, aspirate kerosene diluent to clean the system; if the content of a certain element is too high during measurement, after cleaning with kerosene diluent, check the signal intensity of the element to ensure that the element has been washed away

• 14.4 When internal standard correction is used, many ICP spectrometers are equipped with software that can automatically calculate and establish calibration curves; the element emission intensity is proportional to the internal standard element emission intensity; the calibration curve is the relationship curve between the intensity of the element in the working standard (Rww) and its concentration in the calibration standard; the converted intensity of the element in the working curve is calculated according to formula (1):

  Rws = (Iws − Iblank) / Iinst ………………(1)

  Where:

  • Rws — intensity ratio of element e in the working curve;
  • Iws — emission intensity of element e in the working standard;
  • Iblank — emission intensity of element e in the kerosene diluent;
  • Iinst — emission intensity of the internal standard element in the working standard.

  (Note: formula (1) source-text extraction in the source text contains noise, symbols require confirmation against the source standard (source-text extraction))

8.4 Test Procedure (Chapter 15)

• 15.1 Determine the detection limits of all elements to be determined as follows: pipette 1000 μL internal standard element stock solution into a 60 mL volumetric flask, add kerosene diluent to the mark, cap the bottle and mix thoroughly to prepare a kerosene diluent containing the internal standard; measure the kerosene diluent containing the internal standard ten consecutive times for the elements to be determined under the same conditions/parameters as during two-point calibration; the software of the ICP spectrometer can calculate the standard deviation of the ten measurement results for the elements to be determined; three times the standard deviation of each element is the detection limit of that element; the detection limit shall be re-determined after each calibration

• 15.2 Measure fuel samples under the same conditions and parameters using the two-point calibration method; between two fuel samples, aspirate kerosene diluent to clean the influence brought to the system by elements from the previous sample; the ICP spectrometer software calculates the mass fraction for each element

• 15.3 Similar to the calibration in clause 14.4, calculate the emission intensity of the element in the sample according to formula (2):

  Re = Ie / Iinst ………………(2)

  Where:

  • Re — intensity ratio of element e in the fuel;
  • Ie — emission intensity of element e in the fuel;
  • Iinst — emission intensity of the internal standard added to the fuel.

  Therefore, against the calibration curve, the ICP instrument software can calculate the mass fraction of the element according to formula (3):

  Ce = (Re × Ccs) / Rws ………………(3)

  Where:

  • Ce — mass fraction of element e in the fuel, in milligrams per kilogram (mg/kg);
  • Ccs — mass fraction of element e in the calibration standard solution, in milligrams per kilogram (mg/kg);
  • Re — intensity ratio of element e in the fuel;
  • Rws — intensity ratio of element e in the working curve.

• 15.4 After every 5 fuel samples are measured, measure one standard check solution (see 12.4); if the result error exceeds 5%, recalibrate the instrument and measure the previously measured standard check solutions until the previous values are consistent

9. Qualitative and Quantitative Determination and Calculation Formulas

• The mass fraction of the element in the calibration standard solution is calculated according to formula (4):

  Ccs = (M100 / Mcs) × C100 ………………(4)

  Where:

  • Ccs — mass fraction of the element in the calibration standard solution, in milligrams per kilogram (mg/kg);
  • C100 — mass fraction of the element in the organometallic standard substance with nominal 100 mg/kg, in milligrams per kilogram (mg/kg);
  • M100 — mass of the organometallic standard substance with a mass fraction of 100 mg/kg weighed out, in grams (g);
  • Mcs — mass of the standard solution prepared with 100 mg/kg organometallic standard substance and kerosene diluent, in grams (g).

• The mass fraction of the element in the sample is calculated according to formula (3) (see 15.3)

• Qualitative and quantitative method: by comparing the element emission intensities in the fuel sample and the calibration standard solution, the content of the element in the fuel sample is calculated after internal standard correction

10. Precision

• Judge the reliability of test results according to the following provisions (95% confidence level)
• Note: The precision of this standard was determined through statistical calculation between two groups of laboratories. The first interlaboratory study included duplicate measurement results of eight laboratories and twelve fuel samples (six diesel fuels, three jet fuels, and three kerosene samples to which organometallic substances were added to varying degrees but all within the applicable range of this standard). The second interlaboratory study (using only HDPE bottles for sodium analysis) included duplicate measurement results of six laboratories and twelve fuel samples (six diesel fuels, three jet fuels, and three kerosene samples to which organometallic substances were added to varying degrees but all within the applicable range of this standard).

10.1 Repeatability

For the same operator, in the same laboratory, using the same instrument, correctly applying this method to conduct continuous measurements on the same test sample, the difference between the two obtained measurement results shall not exceed the value specified in Table 3.

10.2 Reproducibility

Different operators, in different laboratories, using different instruments, correctly applying this method to the same test sample, the difference between two single and independent test results obtained shall not exceed the value specified in Table 3. Taking the element mass fraction as 1.0 mg/kg as an example, the calculated repeatability and reproducibility values are listed in Table 4.

Table 3 Repeatability and reproducibility

Note: a the average mass fraction range of samples in the precision establishment study, in milligrams per kilogram (mg/kg); b X is the average mass fraction, in milligrams per kilogram (mg/kg). (Some exponents source-text extraction in the table are noisy, for example the reproducibility exponent 0.5841 for vanadium is inconsistent with the repeatability exponent 0.3841, requires confirmation against the source standard (source-text extraction))

Table 4 Repeatability and reproducibility calculated using element mass fraction 1.0 mg/kg as an example

(Note: Table 4 source-text extraction is severely incomplete, only part of the data is visible, the rest requires confirmation against the source standard (source-text extraction))

10.3 Bias

Since there is no recognized reference material to determine the bias of this method, there is no statement regarding the bias of this method.

11. Report

Report the mass fraction of the element, in units of mg/kg, with the result retained to two decimal places. If the measured element concentration is below the method detection limit, it shall be reported as "below the detection limit", and the detection limit value of the measured element shall be given.

12. Reference documents

• GB/T 4756 Petroleum liquids — Manual sampling
• GB/T 17476 Standard test method for determination of additive elements, wear metals, and contaminants in used lubricating oils and determination of selected elements in base oils (inductively coupled plasma atomic emission spectrometry)
• GB/T 29114 Gas turbine liquid fuels (the source text source-text extraction is written as GB/T 291/4, requires confirmation against the source standard (source-text extraction))
• ASTM D3605 Determination of trace metals in gas turbine fuels by atomic absorption spectrometry or flame emission spectrometry (Test Method for Trace Metals in Gas Turbine Fuels by Atomic and Flame Emission Spectroscopy)
• MIL-F-16884J Marine distillate fuel United States military standard (Military Specification, Fuel, Naval Distillate)

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