NB/SH/T 0829-2010 Boiling range distribution of petroleum fractions within the boiling range 174℃~700℃ Determination by gas chromatography

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Card type: Test method

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

• Standard number: NB/SH/T 0829—2010
• Chinese name: Boiling range distribution of petroleum fractions within the boiling range 174℃~700℃ Determination by gas chromatography
• English name: Standard test method for boiling range distribution of petroleum distillates in boiling range from 174℃ to 700℃ by gas chromatography
• Replacement relationship: not provided in the available source (the foreword states "this standard is first published")
• Adoption relationship: modified adoption of ASTM D6352-04 (foreword)
• Publication/implementation: published on 2010-05-01, implemented on 2010-10-01 (cover)
• Proposed/administrated/drafted by: proposed by China Petrochemical Corporation; administrated by the Petroleum Fuels and Lubricants Subcommittee of the National Technical Committee for Standardization of Petroleum Products and Lubricants; drafted by the Research Institute of Petroleum Processing, China Petroleum and Chemical Corporation; main drafters Jin Ke, Yang Haiying (foreword)

2. Scope of application and non-applicability

• Applicable: petroleum fractions with an initial boiling point above 174℃ and a final boiling point below 700℃ (C10 to C90) at atmospheric pressure (1.1).
• Not applicable: petroleum or petroleum products containing low relative molecular mass components (such as naphtha, reformate, gasoline, crude oil); substances containing other heteroatom compounds (such as alcohols, ethers, acids or esters) or residuum (1.2).
• Alternative method note: for the above non-applicable substances, refer to SH/T 0558, ASTM D3710 or ASTM D5307 (1.2).
• Deviation note: substances containing large amounts of non-normal paraffins will produce deviations when determined using this standard (see Appendix A) (1.2).
• System of units: International System of Units (SI) is adopted (1.3).
• Safety: this standard does not propose recommendations for all safety issues involved; before use, users should establish appropriate safety protection measures and determine the applicability of relevant regulatory restrictions (1.4).

3. Method principle

• Gas chromatography is used to simulate the conventional distillation method for boiling range distribution determination, using a non-polar open tubular capillary gas chromatography column to make hydrocarbon components in the sample elute in order of increasing boiling point (4.1).
• The sample is diluted with solvent to reduce viscosity and then introduced into the gas chromatograph; sample vaporization uses independent heating at the injection point or heating synchronized with the column temperature (4.2).
• The column temperature is raised at a repeatable linear programmed heating rate so that hydrocarbon components elute in order of increasing boiling point; a flame ionization detector (FID) is used to quantitatively determine the eluted sample; area slices are used to record the detector integrated signal for continuous retention time segments during the analysis (4.3).
• Calibration: determine the retention times of known hydrocarbons within the span of the test method range and correlate them with their boiling point temperatures; using calibration constructed with normal paraffins, calculate the boiling range distribution by normalization; use calibrated retention times to calculate boiling point temperatures and report by each percent yield point (4.4).

4. Reagents and materials (purity / preparation)

• 7.1 Carrier gas: high-purity helium or hydrogen; it is recommended to add purifiers, use molecular sieves or other suitable removal agents to remove water, oxygen and hydrocarbons; adjust sufficient constant carrier gas flow. Warning: helium and hydrogen under high pressure... (the original text is interrupted at source-text extraction, requires confirmation against the source standard (source-text extraction))
• 7.2 Hydrogen: high-purity hydrogen (for example hydrocarbon-free), used as FID combustion gas; hydrogen is also used as carrier gas. Warning: under high pressure hydrogen is a very flammable... (the original text is interrupted at source-text extraction, requires confirmation against the source standard (source-text extraction))
• 7.3 Air: high-purity (for example hydrocarbon-free) compressed air used as FID combustion-supporting gas. Warning: under high pressure compressed air is a gas and supports combustion.
• 7.4 Solvent: unless otherwise specified, analytical reagent grade or higher grade reagents should be used.
  • 7.4.1 Carbon disulfide (CS2): purity greater than 99%, used as a solvent to reduce sample viscosity, can reduce the amount of sample introduced onto the chromatographic column, ensure linear detector response and reduce peak asymmetry; it mixes easily with oils containing asphaltenes and has a small response on FID; before selecting it as a sample diluent, its purity (hydrocarbon content) should be determined. Warning: carbon disulfide is very flammable and toxic.
  • 7.4.2 Cyclohexane (C6H12): purity greater than 99%, used instead of CS2 to prepare calibration mixtures.
• 7.5 Calibration mixture: a mixture of normal paraffins quantitatively dissolved in a suitable solvent (conventionally C10 to C18, as stated in the original text, requires confirmation against the source standard (source-text extraction)). The final concentration is about 1 parts normal paraffins mixed into 200 parts solvent. According to the range specified in this standard (see 1.1), the mixture is required to have at least one compound with a boiling point lower than the initial boiling point of the sample being tested and one higher than its final boiling point. The calibration mixture contains at least 11 known normal paraffins (for example C10, C12, C14, C20, C24, C40, C50, C60, C70, C80 and C90, as stated in the original text, requires confirmation against the source standard (source-text extraction)). The boiling points of normal paraffins at atmospheric pressure are listed in Table 1. Note: a suitable calibration mixture can be obtained by dissolving synthetic wax (such as polywax 655 or polywax 1000) in a volatile solvent (for example CS2 or cyclohexane); prepare a solution of 1 parts synthetic wax to 200 parts solvent; lower-boiling normal paraffins should be added to ensure consistency with clause 7.5. Figure 1 is a typical calibration mixture chromatogram, and Figure 2 is a chromatographic curve for carbon numbers greater than 39.
• 7.6 Response linearity mixture: prepare a mixed solution of about 10 individually quantitatively weighed alkanes (purity greater than 99%) that can cover the boiling range of this standard; the component with the highest boiling point should be at least n-C60 (as stated in the original text, requires confirmation against the source standard (source-text extraction)); the mixture should contain n-C40; use a suitable solvent to prepare a solution with each component mass fraction of 0.5%~2.0%.
• 7.7 Reference oil 5010: a reference test sample determined when multiple laboratories participated in the research for this standard, and its boiling range distribution results are listed in Table 2 (for data in Table 2, see the precision-related table in Section 10).

5. Instruments and equipment

• 6.1 Gas chromatograph: a gas chromatography system with the following performance parameters should be used.
  • 6.1.1 Carrier gas flow control: it is recommended that the system be equipped with a constant pressure/constant flow device capable of maintaining a constant carrier gas flow rate throughout the entire temperature programmed heating process.
  • 6.1.2 Column oven: capable of maintaining constant temperature near ambient temperature (for example 35℃~50℃), and capable of linear programmed temperature operation up to 450℃.
  • 6.1.3 Column programmed temperature: should be capable of linear programmed temperature operation within the range of 450℃ at selectable linear rates up to 28℃/min; sufficiently reproducible so that each component in the calibration mixture described in clause 7.5 obtains a retention time of 0.1min (6s) (the original text here is incomplete at source-text extraction, requires confirmation against the source standard (source-text extraction)).
  • 6.1.4 Detector: hydrogen flame ionization detector (FID), should meet or exceed the following indicators.
    • 6.1.4.1 Operating temperature: up to 450℃.
    • 6.1.4.2 Sensitivity: 0.005C/g (as stated in the original text, requires confirmation against the source standard (source-text extraction)).
    • 6.1.4.3 Minimum detectability: 1×10^-11 g/s.
    • 6.1.4.4 Linear range: 10^6 (as stated in the original text, requires confirmation against the source standard (source-text extraction)).
    • 6.1.4.5 The connection between the chromatographic column and the detector should be made when the column oven is not heated.
  • 6.1.5 Injection system: any injection system that can meet the performance parameters in clause 7.6 may be used; programmed temperature vaporization (PTV) and programmed cold on-column injection systems have been successfully used.
• 6.2 Microsyringe: for on-column injection devices, use a microsyringe with a stainless steel needle whose specification matches the inner diameter of the chromatographic column; a syringe of 6.1N (as stated in the original text, requires confirmation against the source standard (source-text extraction)) 10μL capacity may be used.
• 6.2 (the original text repeats the number, requires confirmation against the source standard (source-text extraction)) It is recommended to use an autosampler to obtain the best precision.
• 6.3 Chromatographic column: this standard specifies the use of a non-polar wall-coated open tubular column (WCOT) with high thermal stability (see note); glass, quartz and stainless steel columns with inner diameters of 0.53mm–0.75mm meet the requirements of this standard; columns with cross-linked or bonded 100% dimethylpolysiloxane stationary phase with liquid film thickness from 0.10μm to 1.0μm may be used; the selection of column length and liquid film thickness is based on the premise of ensuring that at least C90 normal paraffins (boiling point 700℃) can elute from the column; the selected chromatographic column and operating conditions should enable hydrocarbons in petroleum products to be separated in order of increasing boiling point and meet the requirements of 8.2.1; columns with resolution between 3–10 may be used for this standard (as stated in the original text, inconsistent with 8.2.1 "at least 2 and not greater than 4", requires confirmation against the source standard (source-text extraction)). Note: recent information indicates that the true boiling points of all components (equal to equivalent temperature at atmospheric pressure) do not all correspond to retention times on the same line; other chromatographic column systems that can meet this criterion may be considered; these criteria will be determined after completing the round-robin statistical evaluation of this standard.
• 6.4 Recording system: composed of a recorder or equivalent equipment meeting the following requirements.
  • 6.4.1 Recorder: a potentiometric recorder or equivalent equipment with a range of 0mV~1mV, with a full-scale response time of 2s or shorter, capable of providing a graphical display.
  • 6.4.2 Integrator: equipment capable of determining the accumulated area under chromatographic peaks; it may be an electronic integrator or workstation based on a chromatographic data system; the integrator/workstation system should have conventional chromatographic software for determining retention times and chromatographic peak areas (peak detection mode); in addition, the system should be capable of converting the continuous detector integrated signal into area slices at fixed intervals (area slice mode); these collected and analyzed area slices are then stored; the voltage range of the integrator/workstation (for example 1V, 10V, the original text source-text extraction is "1V, 10K", requires confirmation against the source standard (source-text extraction)) should cover the linear range of the potentiometer system used. Note: the operating software installed on the chromatograph allows the mathematical mode of the baseline plot to be stored in memory; in subsequent sample runs, the baseline is automatically subtracted from the detector signal to correct for column bleed; some integration systems can also store and automatically subtract blanks from subsequent determinations.

6. Recommended operating conditions

• Table 3 Typical chromatographic operating conditions (original text Table 3):
  • Instrument: equipped with a cold on-column or programmed temperature vaporization inlet (PTV)
  • Chromatographic column: aluminum-coated quartz capillary column, 5m × 0.53mm inner diameter, liquid film thickness 0.1μm, 100% dimethylpolysiloxane stationary phase
  • Carrier gas: high-purity helium (constant flow mode) 18mL/min
  • Column oven temperature mode: flame ionization detector; air 400mL/min, hydrogen 32mL/min, auxiliary gas (nitrogen) 24mL/min; temperature 450℃; initial temperature 50℃ (the source source-text extraction is "initial temperature 500", requires confirmation against the source standard (source-text extraction)), initial time 0min, programmed temperature ramp rate 10℃/min, final temperature 400℃, final time 6min; equilibration time (not provided in the available source)
  • Injection volume: not provided in the available source
  • Sample dilution: diluted with carbon disulfide, mass fraction is 1%
  • Calibration standard dilution: diluted with carbon disulfide, mass fraction is 0.3% (the source source-text extraction is "0.38", requires confirmation against the source standard (source-text extraction))
• 8.1.1 Place the gas chromatograph and auxiliary equipment according to the manufacturer's instructions; recommended operating conditions are given in Table 3.
• 8.1.2 When connecting the column in Table 4 to ... (the source source-text extraction is interrupted, requires confirmation against the source standard (source-text extraction))
• 8.1.3 FID should be inspected regularly to remove deposits formed by combustion of silicone liquid phase or other substances in the detector; these deposits will alter the response performance of the detector.
• 8.1.4 If the injection system is heated, after installing a new septum a blank should be run to ensure that no additional chromatographic peaks are produced due to septum bleed; at the sensitivity normally used in this standard, the septum should be aged for several hours above the operating temperature of the injection system to minimize this effect; the injection line and the beginning of the column should be inspected and reinstalled regularly, and if necessary, additional deposits or sample residues should be removed.
• 8.1.5 Column aging: a new column needs to be aged above the operating temperature of the test method to reduce or effectively eliminate stationary phase bleed and obtain a stable chromatographic baseline.
• 8.2 System performance requirements:
  • 8.2.1 Column resolution: column resolution affects the determination of the entire boiling range distribution, and resolution is affected by the physical parameters of the column and operating conditions; determine under the same conditions as the sample analysis according to formula (1), and the resolution (R) should be at least 2 and not greater than 4; use C50 and C52 in the measured calibration mixture (or synthetic wax retention time/boiling point mixture) to determine column resolution. Formula (1): R=[2(t2-t1)]/[1.699(w1+w2)] (the source source-text extraction is "R=［2（ 2 t1）1/L1.699（w， +ws）］", requires confirmation against the source standard (source-text extraction)); where t1 is the retention time of n-pentacontane (s), t2 is the retention time of n-dopentacontane (s), w1 is the half-peak width of n-pentacontane (s), w2 is the half-peak width of n-dopentacontane (s).
  • 8.2.2 Detector response calibration: this standard assumes that the response of petroleum product hydrocarbons on FID is proportional to the mass of the individual compound; verification should be performed when the system is placed in service and whenever the system or operating parameters change; use the same operating procedure as for sample analysis (see Chapter 9) to determine the linear response mixture (see Clause 7.6); calculate the relative response factor of each n-alkane (relative to n-tetracontane) according to formula (2). Formula (2): Fi=(Mi·Ai)/(M40·A40) (the source source-text extraction is "P.=（M.A.）/（Mg/4t）", requires confirmation against the source standard (source-text extraction)); where Mi is the mass of the n-alkane in the mixture (g), Ai is the relative peak area of the n-alkane in the mixture, M40 is the mass of n-tetracontane in the mixture (g), A40 is the relative peak area of n-tetracontane in the mixture; the Fi of each n-alkane should remain within ±5% (the source source-text extraction is "=5%", requires confirmation against the source standard (source-text extraction)); the response factors determined by a laboratory are listed in Table 5 (Table 5: carbon number 10 is 0.98, 12 is 0.96, 14 is 0.95, 16 is 0.97, 20 is 0.98, 24 is 0.96, 28 is 1.00, 32 is 0.98, 36 is 0.97, 40 is 1.00, the source source-text extraction data is incomplete, requires confirmation against the source standard (source-text extraction)).
  • 8.2.3 Column temperature: the selected column temperature should allow separation between the solvent and the first n-alkane peak in the calibration mixture (C10) and allow the n-alkane with the highest boiling point (700℃) (C90) to elute from the column before reaching the final temperature; the actual programmed temperature ramp rate used will be affected by other operating variables such as column dimensions, carrier gas type and flow rate, and sample amount; thin liquid films and narrow-bore columns require low carrier gas flow rates and faster temperature program ramp rates to avoid overloading of sample components.
  • 8.2.4 Column elution performance: the column stationary phase is required to be nonpolar and have McReynolds constants X'=15–17, Y'=53–57, Z'=43–46, U'=65–67, S'=42–45 (the source source-text extraction is "*=15–17, Y=53–57, 2=43 –46, U=65–67,8=42–45", requires confirmation against the source standard (source-text extraction)).
• 8.3 Column selection (source Table 4, source-text extraction incomplete):
  • Capillary column dimensions: 5m × 0.53mm inner diameter
  • Capillary column type: polyimide or aluminum-coated quartz capillary column with 0.1μm liquid film thickness of bonded 100% dimethylpolysiloxane; stainless steel column with 5m × 0.53mm inner diameter, 0.1μm liquid film thickness of bonded 100% dimethylpolysiloxane

7. Sampling and sample preparation

• 9.4 Sample preparation: prepare the sample as a solution with a suitable solvent (e.g., CS2 or cyclohexane) and then introduce it into the gas chromatograph.
  • 9.4.1 Place 0.1g–1g of sample into a screw-cap or crimp-top vial (the source source-text extraction is "0.1g–18", requires confirmation against the source standard (source-text extraction)).
  • 9.4.2 Dilute the sample with solvent to a solution with a mass fraction of 1%.
  • 9.4.3 Cap the vial and mix the mixture thoroughly; if necessary, heating may be applied to completely homogenize the solution; however, the sample should be a stable solution and injected at room temperature; if necessary, a more dilute solution may be prepared.

8. Analytical procedure

• 9.1 Analysis sequence: to obtain maximum reproducibility in these tests, edit a sequence table set by analysis events, which includes: the initial startup temperature to which the column oven and inlet are cooled, equilibration time, sample injection and system start, analysis, and final temperature hold time.
  • 9.1.1 After setting the chromatographic conditions to meet performance requirements, program the column temperature to the maximum usable temperature and hold at this temperature for the selected time; according to the established analysis sequence, cool the column to the starting temperature.
  • 9.1.2 During cooling and equilibration, prepare the integrator/computer system; if retention time calibration is performed, use peak detection mode; for sample and baseline determination (with or without solvent injection), operate in area slice mode; this standard requires a slice rate of 1.0Hz (1s^-1); if the time is limited within 0.02% and 0.2% of the retention time of the last calibration component (C90), other slice rates may also be used; before determination of the boiling range distribution, if it is ensured that the accumulated (bundled) slice data are within these limits, other slice rates may also be used for other reasons.
  • 9.1.3 Set the exact time by timetable to inject the calibration mixture, solvent, or sample into the chromatograph; or inject an empty sample (baseline blank); start the chromatographic cycle and integrator/computer data acquisition at injection; repeat all analyses or calibrations according to the established analysis sequence; because complete separation of sample peaks is not expected, do not change the set sensitivity during analysis.
• 9.2 Blank baseline: perform a blank analysis (baseline blank) at least once per day; the blank analysis may be no injection or injection of the same volume of solvent as used for sample determination; rely on the subsequent data processing function for baseline/solvent compensation; a typical blank analysis is completed before sample determination; however, to provide additional data on instrument operation or residual carryover from previous sample determinations, a blank determination may also be performed between two sample determinations or at the end of a sample sequence. Note: if the gas chromatograph already provides automatic baseline correction (see 6.4.2 note), no further area slice correction is required; if the electronic offset of the chromatograph is added to the signal after baseline compensation, additional area slice correction is required to subtract the electronic offset; refer to the instruction manual of the instrument used to determine whether the electronic offset is added to the signal; if the algorithm used is not clear enough, it is necessary to determine whether further correction is necessary by examining the area slice data; determine whether the electronic offset is added to the compensated signal by examining the area slices before any chromatographic peak elutes (called corrected area slices); if these corrected area slice values (representing the true baseline) deviate from zero, then in subsequent analyses the average of these corrected area slices should be subtracted from each corrected area slice.
• 9.3 Retention time versus boiling point calibration: calibration of retention time versus boiling point should be performed on the same day as the sample analysis; inject an appropriate amount (0.2μL~2.0μL) of calibration mixture (see 7.5) into the chromatograph, using the analysis sequence settings, to obtain a conventional (peak detection) data record of the measured peak retention times and peak areas of each component; if a boiling point distribution range report is required, collect a record of time slice areas.
  • 9.3.1 Check whether the chromatographic peak shape of the calibration sample is asymmetric (non-Gaussian peak shape); an asymmetric peak shape indicates that the sample is overloaded on the column, which will cause the peak apex to shift relative to a non-overloaded peak; the asymmetry measurement results are given in Table 6; if column overload occurs, it will affect the retention time determination, and therefore the determined boiling point temperature will also have errors; the amount of stationary liquid coated on the column determines the amount of sample that can be tolerated; reduce the injection volume or further dilute the sample and reanalyze the calibration sample to avoid chromatographic peak distortion. Table 6: resolution between 1-C50 and n-C52 3.3; n-C50 asymmetry 10% peak height 1.17, 50% peak height 1.00 (the source source-text extraction is "resolution between 1-Csn and n-Cs" "7-Cso asymmetry", requires confirmation against the source standard (source-text extraction)).
    • 9.3.1.1 Asymmetry calculation: calculate the ratio A/B of the specified peak in the calibration mixture as shown in Figure 3; A is the peak width in seconds at peak height 10% (0.10H) before the peak apex when the peak elutes; B is the peak width in seconds at peak height 10% (0.10H) after the peak apex when the peak elutes; this ratio for n-pentadecane (n-C50) in the calibration sample should not be less than 0.5 or greater than 2.0; Table 6 lists the measurement results from one laboratory.
  • 9.3.2 Based on the analysis of the calibration mixture, establish a calibration table by recording the time at the maximum of each peak and the Celsius boiling point temperature of each component in the mixture; a typical calibration table is listed in Table 7; the boiling point (atmospheric pressure temperature) of each n-alkane is listed in Table 1; Figure 1 is a typical calibration curve graph. Table 7 Typical calibration report (partial): n-C10 boiling point 174℃ retention time 0.25min; n-C12 boiling point 216℃ retention time 0.58min; n-C14 boiling point 254℃ retention time 1.61min; n-C16 boiling point 271℃ retention time 2.40min; n-C18 boiling point 287℃ retention time 3.27min; n-C20 boiling point 302℃ retention time 4.18min; n-C22 boiling point 316℃ retention time 5.07min; n-C24 boiling point 344℃ retention time 6.78min; n-C26 boiling point 369℃ retention time 8.38min; n-C28 boiling point 391℃ retention time 9.84min; n-C30 boiling point 412℃; n-C32 boiling point 431℃; n-C34 boiling point 449℃; n-C36 boiling point 466℃; n-C38 boiling point 481℃; n-C40 boiling point 496℃; n-C42 boiling point 509℃; n-C44 boiling point 522℃; n-C46 boiling point 534℃; n-C48 boiling point 545℃; n-C50 boiling point 556℃; n-C52 boiling point 566℃; n-C54 boiling point 575℃; n-C56 boiling point 584℃; n-C58 boiling point 592℃; n-C60 boiling point 600℃; n-C62 boiling point 615℃; n-C64 boiling point 622℃; n-C66 boiling point 629℃; n-C68 boiling point 635℃; n-C70 boiling point 641℃; n-C72 boiling point 647℃; n-C74 boiling point 653℃; n-C76 boiling point 658℃; n-C78 boiling point 664℃; n-C80 boiling point 670℃; n-C82 boiling point 675℃; n-C84 boiling point 681℃; n-C86 boiling point 686℃; n-C88 boiling point 691℃; n-C90 boiling point 695℃; n-C92 boiling point 700℃; n-C94 boiling point 704℃ (the data in the original Table 7 source-text extraction is incomplete, some retention times are missing, requires confirmation against the source standard (source-text extraction)).
• 9.5 Sample analysis: use the sample sequence settings, inject the sample into the gas chromatograph; continuously collect slices throughout the entire analysis (area slice mode).
  • 9.5.1 Carefully select an injection amount that does not exceed the linear range of the detector; typical injection amounts range from 0.2μL to 2.0μL of diluted sample; the maximum sample signal should not exceed the maximum calibration signal in 9.3.1; Figure 4 is a typical sample chromatogram.
  • 9.5.2 Ensure the baseline is returned to before the sample ends; if the sample chromatographic peaks do not return to baseline at the end of the temperature program, it indicates that the sample has not completely eluted from the chromatographic column, and this sample exceeds the measurement range of this standard.

9. Qualitative and quantitative determination and calculation formulas

• 10.1 Load the sample chromatographic slice integration table. Note: In order to provide a detailed calculation process, the algorithm of this standard is consistent with SH/T 0558 and Appendix B is provided.
• 10.2 Complete slice correction.
  • 10.2.1 Calculate the slice average at the beginning of the chromatographic integration according to the following steps: calculate the average and standard deviation of the first 5 slices in the chromatogram; discard the average of any 5 slices that are not within the standard deviation, then take the subsequent 5 slices again to calculate the average, until it is less than the specified standard deviation; this value will be used to eliminate any baseline rise caused by injection.
  • 10.2.2 Subtract the above-mentioned average slice area of 5 from all area slices obtained from the sample chromatographic analysis; the above-mentioned average slice area is defined as the zero point of the chromatographic peak.
• 10.3 Load the blank run chromatographic slice integration table. Note: For instruments that generate an electronically corrected baseline at the detector and can directly subtract the baseline, the sample can be directly measured or baseline compensation can be performed; if the instrument performs compensation, clauses 10.4 to 10.7 can be skipped.
• 10.4 Perform slice correction on the blank run table according to clause 10.2.
• 10.5 It is required that the slice width of the sample spectrum is the same as the slice width during the blank run.
• 10.6 Subtract the corresponding slice area during the blank run from each area slice collected from the sample measurement.
• 10.7 Subtract the minimum slice value from all corrected slices of the sample spectrum to obtain a chromatogram with slices zeroed.
• 10.8 Drift degree determination:
  • 10.8.1 Calculate the average and standard deviation of the first 5 slice areas in the chromatogram.
  • 10.8.2 Discard the average of any 5 slices that are not within the standard deviation, then take the subsequent 5 slices again to calculate the average, until it is less than the specified standard deviation; this value will be used to eliminate any baseline rise caused by injection.
  • 10.8.3 Define the above-mentioned average slice area value as the initial baseline signal.
  • 10.8.4 Process the last 5 slice areas in the chromatogram in the manner of 10.8.1 and 10.8.2.
  • 10.8.5 Define the above-mentioned average slice area of the last 5 slices as the final baseline signal.
  • 10.8.6 Compare and report the initial and final baseline signals; they should be close.
• 10.9 Determination of the sample start elution time:
  • 10.9.1 Calculate the total area: sum all corrected slice areas in the table; if there is a solvent peak in the sample measurement, start calculating after the solvent peak has completely eluted; otherwise, start calculating from the first slice.
  • 10.9.2 Calculate the rate of change between every two consecutive area slices, starting from the starting slice specified in 10.9.1 and calculating point by point backward; the rate of change is obtained by dividing the area difference between a slice and its adjacent previous slice by the slice width; the time when the first rate of change exceeds the total area (see 10.9.1) 0.001%/s is defined as the sample start elution time.
  • 10.9.3 In order to reduce possible noise or electrical signal interference, it is necessary to use the average of all slices within the 3s time period instead of the single slice area value to determine the start elution time; and in order to eliminate baseline noise interference, it is required that the accumulation period used to calculate the single slice area should be greater than 3s.
• 10.10 Determine the sample end elution time using the following steps:
  • 10.10.1 Calculate the total sample chromatographic area: sum all corrected area slices in the table corresponding to the sample start elution time.
  • 10.10.2 Calculate the rate of change between consecutive area slices, starting from the end point of the run and calculating point by point backward; the rate of change is obtained by dividing the area difference between a slice and its adjacent previous slice by the slice width; the time when the first rate of change exceeds the total area (see 10.10.1) 0.00001%/s is the sample end elution time (the original source-text extraction is "0.00001%", requires confirmation against the source standard (source-text extraction)).
  • 10.10.3 In order to reduce possible noise interference, it is necessary to use the average of all slices within the 3s time period instead of the single slice area value to determine the sample end elution time; and to eliminate baseline noise interference, it is required that the accumulation period used to calculate the single slice area should be greater than 3s.
• 10.11 Calculation of the total sample area: sum all corrected slice areas from the start of sample elution to the end of the run.
• 10.12 Area normalization: divide the total area (10.11) by each slice area in the sample measurement and multiply by 100.
• 10.13 Calculate the boiling range distribution table:
  • 10.13.1 Initial boiling point: sum the sample slices until the sum is equal to or greater than 0.5%; if the sum is greater than 0.5%, interpolate (refer to the algorithm in 10.15.1) to calculate the time when the area reaches 0.5%; calculate the boiling point temperature using the time of this slice corresponding to the calibration table; if necessary, use interpolation (refer to the algorithm in 10.15.2).
  • 10.13.2 Final boiling point: sum the sample slices until the sum is equal to or greater than 99.5%; if the sum is greater than 99.5%, interpolate (refer to the algorithm in 10.15.1) to calculate the time when the area reaches 99.5%; calculate the boiling point temperature using the time of this slice corresponding to the calibration table; if necessary, use interpolation (refer to the algorithm in 10.15.2).
  • 10.13.3 Intermediate boiling point: for each point from 1% to 99%, find the retention time corresponding to the percentage yield area to be determined; operate according to 10.13.1 and 10.13.2, and use interpolation when the cumulative area exceeds the specified yield; determine the boiling point using the calibration table.
• 10.14 Report results:
  • 10.14.1 Print the boiling point distribution table.
  • 10.14.2 Print the operating conditions, slice width, analysis start and end times.
• 10.15 Calculation method:
  • 10.15.1 Calculate the time corresponding to the yield point accounting for X of the total area, X=0.5, 1, 2, …, 99.5%.
    • 10.15.1.1 Record the time of the slice immediately before the slice whose cumulative area is greater than the yield point accounting for X of the total area; this time is T0, and the cumulative area up to this point is A0.
    • 10.15.1.2 Calculate the slice parameter that accurately accounts for the yield point of X of the total area according to formula (3): Ax=(X-A0)/(A0+1-A0) (the original source-text extraction is "Ax=Aotl-A.", requires confirmation against the source standard (source-text extraction)); where Ax is the slice proportion parameter corresponding to the X yield point, A0 is the cumulative area yield up to the slice immediately before the slice corresponding to the cumulative yield X, A0+1 is the cumulative area yield up to the slice corresponding to the cumulative yield X, and X is the cumulative yield at point X.
    • 10.15.1.3 Calculate the time using parameter Ax according to formula (4): T=Ax·W; where W is the slice width, Ax is the slice proportion parameter corresponding to the X yield point, and T is the time of Ax.
    • 10.15.1.4 Record the exact time when the cumulative area equals the yield point accounting for X of the total area, calculated according to formula (5): Tx=T0+T; where T0 is the time of the slice immediately before the slice corresponding to the cumulative yield X, T is the time of Ax, and Tx is the exact time when the cumulative area equals the yield point accounting for X of the total area.
  • 10.15.2 Interpolate and calculate the boiling point corresponding to the retention time of the cumulative area slice.
    • 10.15.2.1 Compare the given time with each corresponding retention time in the calibration table; select the nearest standard retention time that is equal to or greater than the interpolated time. Warning: the retention time table should be selected in order.
    • 10.15.2.2 If the interpolated time equals a standard retention time, record the corresponding boiling point.
    • 10.15.2.3 If the interpolated time does not equal a standard retention time (see 9.3), calculate the boiling point temperature by interpolation as follows.
    • 10.15.2.4 If the interpolated time is less than the first retention time in the calibration table, then extrapolate using the first two components in the table, calculated according to formula (6): BPx=m1·(RTx-RT1)+BP1; where m1=(BP2-BP1)/(RT2-RT1), BPx is the interpolated boiling point, RTx is the interpolated retention time, RT1 is the retention time of the first component in the calibration table, BP1 is the boiling point of the first component in the calibration table, RT2 is the retention time of the second component in the calibration table, BP2 is the boiling point of the second component in the calibration table.
    • 10.15.2.5 If the interpolated time is between the retention times of two components in the calibration table, then interpolate using the two adjacent components in the table, calculated according to formula (7): BPx=m2·(RTx-RT1)+BP1; where m2=(BP2-BP1)/(RT2-RT1), BPx is the interpolated boiling point, RTx is the interpolated retention time, RT1 is the retention time of the preceding component in the calibration table, BP1 is the boiling point of the preceding component in the calibration table, RT2 is the retention time of the following component in the calibration table, BP2 is the boiling point of the following component in the calibration table.
    • 10.15.2.6 If the interpolated time is greater than the last retention time in the calibration table, then extrapolate using the last two components in the table, calculated according to formula (8): BPx=mn·(RTx-RTn-1)+BPn-1; where mn=(BPn-BPn-1)/(RTn-RTn-1), BPx is the interpolated boiling point, RTx is the interpolated retention time, RTn-1 is the retention time of the second-to-last component in the calibration table, BPn-1 is the boiling point of the second-to-last component in the calibration table, RTn is the retention time of the last component in the calibration table, BPn is the boiling point of the last component in the calibration table.
• Appendix B (Informative Appendix) Calculation Algorithm:
  • B.1 Overview: This standard includes a detailed calculation process; this appendix is provided in order to give the detailed calculation process and to make the algorithm of this standard consistent with SH/T 0558.
  • B.2 Required elements:
    • B.2.1 Sample array: N area slices; data should be collected at the minimum sample frequency of 5Hz–10Hz (i.e., slice width 0.25–0.1s); in addition, the slice width should be such that from the first 10 slice to the 20 slice there is no sample or solvent elution.
    • B.2.2 Blank array: N area slices; the blank slice width should be the same as the sample slice width (if electronic baseline subtraction is used, the blank array is not required, see B.3.1).
      • B.2.2.1 The analysis conditions for the blank and the sample should be the same up to the end point of the analysis.
      • B.2.2.2 The number of slices in the blank array should be equal to or greater than the number of slices in the sample analysis; if the number of slices in the blank array is greater than the number of slices in the sample analysis, then the excess slices in the blank array will be cancelled; this occurs if the blank run exceeds the termination point range of the sample determination.
    • B.2.3 Retention times of n-alkanes: the retention times of the individual n-alkanes in the calibration mixture should be obtained from the peak data file obtained by running the calibration mixture under the same conditions as the sample and blank.
    • B.2.4 Boiling points of n-alkanes: the boiling points of the individual n-alkanes in the calibration mixture can be obtained from Table 1 of this standard (nearest to C number).
    • B.2.5 Solvent elution time: solvent elution time refers to the time when the signal returns to baseline after the solvent has eluted; if available, use this parameter to remove the area produced by the solvent; if solvent is used, the detector signal should return to baseline before any sample component elutes.
  • B.3 Subtract blank from sample (see note):
    • B.3.1 Subtract the blank area slices from the actually collected sample area slices; correct the sample area slices with the blank. Warning: many instruments have an automatic baseline subtraction function that can be used; however, automatic baseline subtraction may not give the same result on a slice-by-slice basis; on some instruments, when automatic baseline subtraction is used, the subtracted baseline will show an abnormal shape when the temperature-programmed oven temperature reaches its maximum and is held for a period of time or near this point; this abnormal shape appears as the baseline slowly rising, then relatively suddenly dropping, and then becoming a flat baseline; when the observed values are very small (only a few pA), the range of the sudden drop fully meets the requirements for determining the end of sample elution; an erroneous signal generated at the end of the sample will cause FBP to be too high; if an erroneous signal is generated and cannot be eliminated, the user should skip the instrument's automatic baseline subtraction function, skip B.2; in this case, use the corrected area that zeroes the sample array in the subtraction calculation. Note: the original text here source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction).
  • B.4 Data:
    • B.4.1 Calculate the average of the first 10–20 (5Hz–10Hz) area slices in the blank-subtracted array.
    • B.4.2 Subtract the above from each area slice in the blank-subtracted array