NB/SH/T 0656-2017 Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants — Elemental Analyzer Method

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Incomplete source card: Sections 13, 14 are absent from the available source. Only available content is translated; source completion is pending.

Card type: Test method

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

• Standard number: NB/SH/T 0656—2017
• Chinese title: Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants — Elemental Analyzer Method
• English title (original text): Stamdard test mmethods for instrummental deerminatiom of carlom, haydrogem, and mitrogen in petroleum pproducts and Iuloricamts (requires confirmation against the source standard (source-text extraction), suspected to be Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants)
• Replacement relationship: replaces SH/T 0656—1998 (2004) "Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants (Elemental Analyzer Method)"
• Adoption relationship: modified adoption using the redrafting method of ASTM D5291-10 (2015)
• Method numbers: this standard includes four methods: Method A, Method B, Method C, and Method D
• Publication/implementation: published on 2017-12-27, implemented on 2018-06-01; issued by the National Energy Administration
• Previous versions: SH/T 0656—1998

2. Scope of application and non-applicability

• Scope of application: specifies the analytical method for determining total carbon, total hydrogen, and total nitrogen content in petroleum products and lubricants using an elemental analyzer; applicable to the determination of carbon, hydrogen, and nitrogen content in samples such as crude oil, fuel oil, additives, and residual oil.
• Mass fraction determination ranges: carbon 75%~87%, hydrogen 9%~16%, nitrogen 0.1%~2%.
• Method D can detect a minimum nitrogen content in lubricating oil with a mass fraction of 0.1%.
• Not applicable: not applicable to the determination of light petroleum products and/or those with a nitrogen mass fraction less than 0.75%, such as gasoline, jet fuel, naphtha, diesel, or chemical solvents; not applicable to the determination of volatile petroleum products, such as gasoline, blended gasoline with oxygen-containing compounds, or gasoline-type aviation turbine fuel.
• Note: In Chapter 1 of the original text, both "nitrogen content 0.1%~2%" and "not applicable to the determination of ... nitrogen mass fraction less than 0.75%" appear, which is contradictory; requires confirmation against the source standard (source-text extraction).

3. Method principle

• 3.1 Carbon, hydrogen, and nitrogen are determined simultaneously in one test procedure. Some system analysis procedures are automatically program-controlled from sample weighing, sample introduction into the inlet, to initialization; some system analysis procedures are manually controlled.
• 3.2 The actual procedures of different instruments vary greatly; the following is a procedure that satisfies the test:
  • 3.2.1 All test samples are converted into carbon dioxide, water vapor, and nitrogen gas.
  • 3.2.2 These gases are quantitatively determined in a suitable gas stream.
• 3.3 In the presence of pure oxygen, the sample is burned at high temperature, and the test sample is converted into corresponding gases, which may produce the following gaseous substances:
  • 3.3.1 Carbon dioxide generated by the oxidation of organic carbon and elemental carbon.
  • 3.3.2 Hydrogen halides obtained from organic halides (and organic hydrogen).
  • 3.3.3 Water vapor obtained from the oxidation of the remaining organic hydrogen and laboratory moisture.
  • 3.3.4 Nitrogen gas and nitrogen oxides obtained from the oxidation of organic nitrogen.
  • 3.3.5 Sulfur oxides obtained from the oxidation of organic sulfur. In some systems, sulfurous acid and sulfuric acid may also be obtained by the combination of sulfur oxides and water vapor.
• 3.4 Several feasible separation and quantitative determination methods for the measured gaseous products:
  • 3.4.1 Method A: In the auxiliary combustion zone, calcium oxide is used to remove sulfur oxides from the combustion gas stream. The remaining gas is carried by helium through high-temperature copper to remove excess oxygen, reduce nitrogen oxides to nitrogen gas, pass through sodium hydroxide to remove carbon dioxide, and pass through magnesium perchlorate to absorb moisture. The remaining nitrogen gas is measured by a thermal conductivity detector, and carbon and hydrogen are measured simultaneously with nitrogen by using infrared detectors to measure carbon dioxide and water vapor content, respectively.
  • 3.4.2 Method B: The combustion product gas stream containing carbon dioxide, water vapor, and nitrogen (with sulfur oxides and excess oxygen already removed as in 3.4.1) is introduced into a mixing chamber and thoroughly mixed at precise volume, temperature, and pressure. After mixing, the pressure in the mixing chamber is reduced, and the gas is passed through a heated chromatographic column, where the gases are separated according to selected retention times. The separation of nitrogen, carbon dioxide, and water vapor is produced by a segmented steady-state method.
  • 3.4.3 Method C: The combustion product gas stream after sufficient oxidation of each component gas is passed through high-temperature copper to remove excess oxygen and reduce nitrogen oxides to nitrogen gas. Then, the gas passes through a high-temperature chromatographic column, separating the gases in the order of nitrogen, carbon dioxide, and water vapor. The eluted component gases are measured with a thermal conductivity detector.
  • 3.4.4 Method D: The organic sample is placed in an oxidizable metal, lightweight container, and then introduced at a preset time into a vertical quartz, nickel-cadmium-iron alloy, or stainless steel reaction tube heated to 1050°C, with carrier gas helium continuously flowing through the reaction tube. The sample is added, and during sample combustion, sufficient high-purity oxygen is temporarily added to the nitrogen stream. Flash combustion occurs in the oxidation tube. The gas stream passes through chromium trioxide and copper oxide to complete quantitative combustion. The mixed combustion gas stream passes through about 640°C copper (840°C steel reactor) to eliminate excess oxygen; then it is immediately introduced into a chromatographic column heated to about 120°C (the Flash EA 1112 fully automatic elemental analyzer only needs to be heated to 50°C). The components are separated by elution through a dedicated Poropak column in the order of nitrogen, carbon dioxide, and water vapor (the activated carbon column is specifically used for the Flash EA 1112 fully automatic elemental analyzer for nitrogen determination), and then measured with a thermal conductivity detector. The percentage content of elements in the sample can be calculated by dedicated software. The instrument is calibrated with standard substances of pure organic compounds. The K coefficient or linear regression can be used for instrument calibration. A typical operating analysis time for one sample is 4min, and the total time is generally 8min.
• 3.5 In all cases, the carbon, hydrogen, and nitrogen concentrations are calculated from the following factors:
  • 3.5.1 The measured instrument response values.
  • 3.5.2 The response value per unit mass of each element (established through instrument calibration).
  • 3.5.3 The mass of the test sample.
• 3.6 The instruments used in the four test methods should have automatic calculation functions.

4. Reagents and materials (purity / preparation)

• 6.1 Reagent purity: Unless otherwise specified, the reagents used in this standard are of analytical grade. Reagents of other grades may also be used if their purity is sufficiently high and will not affect the accuracy of the determination.
• 6.2 Calibration standards: Table 1 lists commonly used pure organic compounds for calibrating the instrument according to 3.4.1~3.4.3; other suitable compounds may also be used.
• Table 1 Standard samples for carbon, hydrogen, and nitrogen instrumental analysis (unit: % (mass fraction))

Note: The molecular formulas and some hydrogen/nitrogen values in Table 1 have obvious source-text extraction noise, all marked as requires confirmation against the source standard (source-text extraction); the correspondence between the nitrogen column values and compounds in Table 1 of the original text may be misaligned, requires confirmation against the source standard (source-text extraction).

• 6.3 Carrier gas and combustion gases:
  • 6.3.1 Oxygen: high-purity oxygen, purity not less than 99.998%.
  • 6.3.2 Helium: high-purity helium, purity not less than 99.995%.
  • 6.3.3 If necessary, compressed air, nitrogen, or argon may be used to drive pneumatic valves.
  • 6.3.4 Carbon dioxide.
  • 6.3.5 Acetone.
  • 6.3.6 Degreasing solvent.
• 6.4 Other reagents and materials:
  • 6.4.1 All reagents and materials included in this standard shall meet the requirements of 5.2.2 and 5.2.3. These reagents and materials may vary greatly for different instruments; some important reagents and materials may be recommended by the instrument manufacturer.
  • 6.4.2 Sodium hydroxide-coated silica, quartz wool, magnesium perchlorate, copper granules, coated calcium oxide (combustion agent), nitrogen catalyst, magnesium oxide for liquid samples.
  • 6.4.3 EA 1000 Reagents: silver tungstate on magnesium oxide, silver vanadate, quartz wool, silver gauze, copper oxide, tungsten oxide, cobalt oxide, copper granules, sodium hydroxide on silica, aluminum oxide, magnesium perchlorate, platinum gauze. Note: The supplier of EA1000 reagent is PerkinElmer, Inc., USA; EA1000 reagent is a registered trademark of PerkinElmer, Inc.
  • 6.4.4 Method C and Method D: quartz wool, chromium oxide (oxidation catalyst), cobalt oxide on silver, reduced copper (reduction catalyst), magnesium perchlorate, molecular sieve: 3A (1.6mm), sodium hydroxide on silica, red diatomaceous earth support (absorbent for liquid samples), copper granules.
• 6.5 Quality control sample (QC): a relatively stable and representative sample of one or more liquid petroleum materials. These QC samples can be used to verify the effectiveness of the test procedure, see Chapter 12.

5. Apparatus and Equipment

• 5.1 General: Because various instrument components and configurations can meet the requirements of these test methods, this standard does not specify the design of the entire system.
• 5.2 Instrument: The function of the instrument shall meet the following requirements.
  • 5.2.1 The combustion conditions for the test specimen shall be such that (within all suitable sample ranges) all components to be determined are completely converted to carbon dioxide, water vapor (unless hydrogen is combined with volatile halogens and sulfur oxides), and nitrogen or nitrogen oxides. Generally, instrument conditions affecting complete combustion include the effectiveness of the oxidant, temperature, and time.
  • 5.2.2 Typical combustion gases shall be treated.
    • 5.2.2.1 Hydrogen present as hydrogen halides and oxyacids of sulfur shall be released as water vapor.
    • 5.2.2.2 Nitrogen present as nitrogen oxides shall be reduced to nitrogen gas.
  • 5.2.3 The water vapor and nitrogen obtained shall be components present in the sample.
  • 5.2.4 Additional treatment of components (before detection) depends on the detection scheme used by the instrument. Note: These additional treatments provided by the instrument components shall satisfy 5.2.2.
  • 5.2.5 The detection system (over its entire range) shall be capable of separately determining the analyzed gases without interference. The analysis process of each sample shall not interfere with the analysis process of other samples.
    • 5.2.5.1 The detector shall provide a linear response representing concentration for suitable samples over the entire possible concentration range.
    • 5.2.5.2 In order to accurately calibrate the concentration of the components to be determined, the system shall include equipment suitable for evaluating non-linear responses.
  • 5.2.6 These devices may be an integral part of the instrument or may be provided by auxiliary parts.
  • 5.2.7 These systems shall directly output concentration data; therefore, the instrument shall include appropriate detector response readout devices.
• 5.3 Consumables:
  • 5.3.1 Tin capsules, in two sizes, large and small.
  • 5.3.2 Ceramic crucible.
  • 5.3.3 Copper capsules.
  • 5.3.4 Tin plugs.
  • 5.3.5 Tin boat (requires confirmation against the source standard (source-text extraction), suspected to be "tin pan" or "tin boat").
  • 5.3.6 Copper plugs.
  • 5.3.7 Aluminum capsules.
  • 5.3.8 Combustion tube.
  • 5.3.9 Absorption tubes (water removal tube and carbon dioxide removal tube).
  • 5.3.10 Nickel capsules.
  • 5.3.11 Reduction tube.
• 5.4 Analytical balance: sensitivity 0.00001g.
• 5.5 Syringe or pipette: used to transfer the test specimen into the capsule.

6. Recommended Operating Conditions

• 9.1.2 Typical instrument operating conditions for Method A:
  • 9.1.2.1 Temperatures: combustion furnace 950°C (primary combustion zone); combustion furnace 950°C (secondary zone); catalyst heater 750°C; column oven 53°C.
  • 9.1.2.2 The pressures of oxygen and carrier gas helium shall be set to 275.8kPa respectively.
  • 9.1.2.3 Typical gas flow rates: helium 400mL/min (normal flow rate), 70mL/min (protective flow rate); oxygen 7L/min; air 6L/min.
• 9.2.2 Typical instrument operating conditions for Method B: combustion temperature 975°C; reduction temperature 640°C; detector heating box temperature 80°~84°C; helium 137.9kPa; oxygen 110.3kPa; air, nitrogen or argon 413.7kPa.
• 9.3.3 Typical instrument operating conditions for Method C: combustion temperature 1020°C; reduction temperature 650°C; detector heating box temperature 60°C–100°C (requires confirmation against the source standard (source-text extraction), original text is "60°C–100°"); detector heating wire temperature 190°C; analysis cycle 420s; autosampler injection: start 20s; autosampler return: stop 70s; oxygen addition time 70s; integration window delay 2s.
• 9.3.4 Typical gas flow rate settings for Method C are shown in Table 2:

• 9.4.3 Typical instrument operating conditions for Method D are shown in Table 3:

Note: The meanings and units of parameters such as "furnace temperature" and "detector heating wire" in Table 3 require confirmation against the source standard (source-text extraction).

7. Sampling and Test Specimen Preparation

• 7.1 Laboratory sample: Take a representative sample in the amount specified in GB/T 4756 or GB/T 27867.
• 7.2 Test specimen: Take a portion from the laboratory sample as the test specimen as follows.
  • 7.2.1 Preparation: Heat the viscous test specimen until it is fluid, and shake 5s.
  • 7.2.2 Transfer: As described in Chapter 9, use a suitable, clean syringe or pipette to transfer the test specimen into the capsule.
• Sample mass for each method:
  • Method A (9.1.1): Weigh approximately 50mg~200mg of homogeneous test specimen into the capsule, accurate to ±1mg, and flatten the capsule with tweezers until sealed. 9.1.1.1 Weigh solid test specimens in tin capsules. 9.1.1.2 Weigh liquid samples in copper capsules, and add magnesium oxide to adsorb the test specimen. Seal the copper capsule with a tin plug.
  • Method B (9.2.1): Weigh approximately 2mg~4mg of homogeneous test specimen into the capsule (accurate to ±0.02mg). Use tweezers to flatten and fold it at the center of the capsule, then use tweezers to flatten it and fold it again.
  • Method C (9.3.1): Weigh approximately 5mg of homogeneous test specimen into a tin capsule (accurate to ±0.02mg). Flatten the capsule with tweezers until sealed. 9.3.2 For liquid samples, after weighing the liquid sample, add about 30mg of red diatomaceous earth support to the tin capsule.
  • Method D (9.4.1): Sample according to the provisions of GB/T 4756 or GB/T 27867. For determination of nitrogen content, weigh approximately 5mg–12mg of homogeneous test specimen into the capsule; for determination of carbon, hydrogen, and nitrogen content, weigh approximately 2mg–3mg of homogeneous test specimen into the capsule (accurate to ±0.02mg). Flatten and seal the capsule with tweezers. 9.4.2 For all liquid samples (100°C kinematic viscosity less than 10mm²/s–50mm²/s), add 10mg–30mg of red diatomaceous earth support. The mass of the red diatomaceous earth support is not included in the sample mass. Lubricant samples generally do not require the addition of red diatomaceous earth support, but for volatile liquid samples, adding red diatomaceous earth support is still useful.

8. Analysis Procedure

• 8 Instrument preparation:
  • 8.1 Prepare the instrument system strictly in accordance with the instrument instructions.
  • 8.2 Calibrate the system according to the calibration procedure specified in the instrument instructions, using acetanilide or a suitable standard sample mentioned in Table 1.
  • 8.3 Preparation of tubes and columns: Before use, clean all quartz and glass components with soap, water, and acetone. Before inserting the tubes into the high-temperature furnace, remove dry fingerprints from the components with a degreasing solvent such as acetone. When handling the tubes, wear suitable gloves, such as lint-free cotton gloves, to prevent leaving fingerprints on the tubes. Note: All combustion tubes and absorption tubes are replaced after 50~300 sample analysis runs. The exact replacement interval shall be determined according to the instrument instructions.
    • 8.3.1 Method A:
      • 8.3.1.1 Combustion tube: Load 50mm quartz wool at the inlet end at the bottom of the tube. Place a ceramic crucible on top of the quartz wool. Then place 31mm quartz wool at the outlet end of the tube. On top of the quartz wool, fill 63mm combustion agent. On top of the combustion reagent, place 119mm quartz wool.
      • 8.3.1.2 Reduction tube: Insert a copper plug at the bottom of the tube. On top of the copper plug, fill 88mm "nitrogen" catalyst. On top of the "nitrogen" catalyst, add 138mm copper granules.
    • 8.3.2 Method B:
      • 8.3.2.1 Combustion tube: preheat EA1000 reagent and magnesium oxide coated with silver tungstate at 900°C to 10min~30min. Roll up a piece of silver mesh, its size should be suitable for insertion into the combustion tube. Clean the rolled silver mesh with detergent and water, then dry it or pass it quickly through the flame several times until the smoke disappears. From the inlet end of the tube, insert 25mm quartz wool until it touches the groove of the tube. Add 50mm of EA1000 reagent. Add a small wad of quartz wool on top. Add 50mm silver tungstate-coated magnesium oxide. Add a small wad of quartz wool on top. Add 25mm silver vanadate, add a small wad of quartz wool on top. Slide the rolled silver mesh into the combustion tube, at this time there is still about 12mm space in the tube. Insert 12mm quartz wool from the inlet end of the combustion tube. Then insert the bottle stopper from the outlet end into the combustion tube.
      • 8.3.2.2 Reduction tube: insert a small wad of quartz wool at the wider inlet end of the tube. Then insert the treated rolled silver mesh. The filling of this tube is done from the outlet end. First load copper granules, tap gently while loading, load until the copper column is 238mm. Then, load a small wad of quartz mesh, add 12mm copper oxide, then load a small wad of quartz wool, finally insert the copper stopper at the outlet end of the reduction tube.
    • 8.3.3 Method C and Method D:
      • 8.3.3.1 Combustion reaction tube: at the bottom of the tube load 2mm quartz wool, fill with 50mm silver coated with cobalt oxide, load 10mm thick quartz wool. Add 120mm chromium oxide. Load 10mm thick quartz wool, place the combustion tube into the combustion furnace, and fix it with a “O” shaped connector.
      • 8.3.3.2 Reduction reaction tube: at the bottom of the tube load 5mm quartz wool, fill with reduced copper, then load 10mm thick quartz wool, place the reduction tube into the reduction furnace, and fix it with a “O” shaped connector.
      • 8.3.3.3 Dehydration tube: at the bottom of the tube load 10mm quartz wool. Fill with 3A (1.6mm) molecular sieve or magnesium perchlorate. Load 10mm thick quartz wool, fix it on the support of the dehydration tube.
      • 8.3.3.4 Carbon dioxide removal tube: first at the bottom of the tube load 10mm quartz wool. Then load 50mm magnesium perchlorate, add 130mm sodium hydroxide-coated silica. Then add 50mm magnesium perchlorate. Then add 10mm thick quartz wool. Fix this tube on the support of the carbon dioxide removal tube.
      • 8.3.3.5 Purification tube: at the bottom load a small amount of cotton or quartz wool, then load 25.4mm silica gel as indicator (magnesium perchlorate), then load about 1/4 tube length of molecular sieve, fill the top with soda lime. Ascarite can also be used to remove carbon dioxide, magnesium perchlorate can be used to remove water. If soda lime is used, a drop of water should be added to the soda lime to activate it. Note: If the gas purity as described in 9.4.3 is used, the purification tube is not required.
• 9 Test procedure:
  • 9.1 Method A:
    • 9.1.1 Weighing and sealing (see Section 7).
    • 9.1.2 Typical instrument operating conditions (see Section 6).
    • 9.1.3 Start the analysis program, run three to four blank sealed shells, then run with a standard sample (requires confirmation against the source standard (source-text extraction), suspected to be “one standard sample”), the blank result should be within ±10%, the standard sample result should be within ±1% of the theoretical value.
    • 9.1.4 All results are stored, and the best value is retrieved for calibration. Input these results and the known calibration sample concentrations into the microprocessor to obtain a single-point calibration curve.
    • 9.1.5 Analyze the standard sample again to check the new calibration curve. The standard sample result should be repeatable or the difference should be less than 1%, otherwise recalibration is required.
    • 9.1.6 Burn the sealed sample in a manner similar to the standard sample. According to the sample result, set the oxygen amount and combustion time to overcome incomplete combustion.
  • 9.2 Method B:
    • 9.2.1 Weighing and sealing (see Section 7).
    • 9.2.2 Typical instrument operating conditions (see Section 6).
    • 9.2.3 Run two to four blank sealed shells in the system, run one sample after every blank. Repeat this operation.
    • 9.2.4 Run one standard sample to obtain the response factor (K), calculated as follows: the detector count for the standard sample divided by the mass of nitrogen, carbon or hydrogen in the standard sample.
    • 9.2.5 If the obtained response factor value is within the range specified in the manual, the sample can be run.
  • 9.3 Method C:
    • 9.3.1 Weighing and sealing (see Section 7).
    • 9.3.2 Liquid sample with red diatomaceous earth carrier (see Section 7).
    • 9.3.3 Typical instrument operating conditions (see Section 6).
    • 9.3.4 Typical gas flow rate settings are shown in Table 2 (see Section 6).
    • 9.3.5 Start the analysis program, first run an unweighed sample to determine the retention time, then run one to two blank sealed shells, then run two to three standard samples to calculate the response factor (K), or run 3 to 6 standard samples to obtain a linear regression curve. Then run the sample.
    • 9.3.6 During the analysis of samples, randomly insert standard samples to check and update the calibration curve. The number of standard sample analyses depends on the sample type and whether the analysis conditions change. Generally, one standard sample is run for every 10 samples.
  • 9.4 Method D:
    • 9.4.1 Weighing and sealing (see Section 7).
    • 9.4.2 Liquid sample with red diatomaceous earth carrier (see Section 7).
    • 9.4.3 Typical instrument operating conditions are shown in Table 3. The purity of oxygen is at least 99.995%, and that of helium should be at least chromatographic grade. These recommended settings should follow the instrument manufacturer's instructions.
    • 9.4.4 Start the analysis program, run 2 blank sealed shells, then run two to three atropine or other standard samples to calculate the response factor. Or run 3 to 6 calibration samples to calculate the linear regression, then run unknown samples.
    • 9.4.5 After instrument calibration, to verify the curve, run a blank, then run a standard sample or QC sample again.
    • 9.4.6 During the analysis of samples, randomly insert standard samples to check and update the calibration curve. The number of standard sample analyses depends on the sample type and whether the analysis conditions change; however, generally one standard sample is run for every 10 to 20 samples.
    • 9.4.7 Any change in the instrument requires re-inspection. Follow the instrument manual.

9. Qualitative and quantitative and calculation formulas

• 10.1 The carbon, hydrogen and nitrogen content in the sample is calculated according to formula (1):
  • A = (B × E × F) / (C × D)
  • Where:
    • A— The content of carbon, hydrogen and nitrogen in the sample, mass fraction, %;
    • B— The response value of the detector to carbon, hydrogen or nitrogen in the sample after subtracting the blank;
    • C— The response value of the detector to carbon, hydrogen or nitrogen in the standard sample after subtracting the blank;
    • D— Sample mass, in milligrams (mg);
    • E— Standard sample mass, in milligrams (mg);
    • F— The content of carbon, hydrogen or nitrogen in the standard sample, mass fraction, %.
• 10.2 The instrument system applying the test method given in this standard will automatically provide the calibration curve.
• 11 Expression of results: The test results for carbon, hydrogen and nitrogen are reported as mass fraction, and the test results are generally retained to two decimal places.

10. Precision

• 13 Precision and bias: Judge the reliability of the test results according to the following provisions (95% confidence level).
• 13.1 Repeatability, r: In the same laboratory, by the same operator using the same instrument, using the same method, the difference between two test results obtained from continuous determination of the same sample shall not be greater than the values in Table 4 and Table 5.
• 13.2 Reproducibility, R: In different laboratories, by different operators using different instruments, using the same method, the difference between two single, independent results obtained from determination of the same sample shall not be greater than the values in Table 4 and Table 5.
• Table 4 Repeatability and reproducibility of Method A, Method B and Method C (unit: mass fraction, %)

X: The average of two test results.

• Table 5 Repeatability and reproducibility of Method D (unit: mass fraction, %)

X: The average of two test results.

• Note: Based on the precision given in clauses 13.1 and 13.2, the typical precision values for carbon, hydrogen and nitrogen given in Table 6 are acceptable.
• Table 6 Typical precision values (unit: mass fraction, %)

Note: The concentration values corresponding to carbon and hydrogen in Table 6 are not provided in the available source; source-text extraction appears as garbled text “qba6 b8soUS”, requires confirmation against the source standard (source-text extraction).

• 13.3 Bias: Because there are no acceptable petroleum-based reference materials applicable to determining the operational bias of these test methods for carbon, hydrogen, and nitrogen in petroleum products and lubricants, the bias cannot be determined.

11. Report

• 11 Expression of results: The test results for carbon, hydrogen, and nitrogen are reported as mass fractions, and the test results are generally retained to two decimal places.
• 12 Quality control:
  • 12.1 Confirm the performance of the instrument and the test procedure by analyzing a quality control sample (QC) (see 6.5).
    • 12.1.1 If the laboratory has established quality control and quality assurance procedures and has demonstrated the reliability of the test results, this procedure may be used.
    • 12.1.2 If the laboratory has not established quality control and quality assurance procedures, refer to the steps in Annex A to establish a quality control procedure.
• Annex A (informative annex) Quality control monitoring:
  • A.1 Confirm instrument performance and the test procedure by analyzing a quality control sample (QC).
  • A.2 Before monitoring the measurement process, users of this standard need to determine the mean value and control limits of the quality control sample (see NB/SH/T 0843).
  • A.3 Record the QC results, and determine the statistical control state of the overall test process based on control charts or other statistical means (see NB/SH/T 0843). Study any data that exceed the control limits and find the cause of the exceedance. The results of this investigation may require recalibration of the instrument, but this is not necessary.
  • A.4 The frequency of QC testing depends on the critical point of analytical quality control, the stability of the test process, and customer requirements. Usually, on the day of routine testing, a QC sample should be analyzed. When a large number of samples are analyzed routinely, the frequency of QC analysis should be increased. When it is demonstrated that testing is under statistical control, the frequency of QC testing may be reduced. The precision of QC sample testing should be checked periodically and compared with the precision of this standard to confirm data quality (see NB/SH/T 0843).
  • A.5 If possible, it is recommended to use a representative routine analysis sample as the QC sample, with a sufficient amount of the QC sample to meet the analytical needs over a period of time; the QC sample should be homogeneous and stable under the current storage conditions.
  • A.6 For details on QC and statistical analysis techniques for control charts, see NB/SH/T 0843.

12. Normative references

• GB/T 4756 Petroleum liquids — Manual sampling
• GB/T 27867 Petroleum liquids — Pipeline sampling
• NB/SH/T 0843 Evaluation of analytical testing systems in the petrochemical industry — Statistical techniques
• GB/T 1