NB/SH/T 0889-2014 Determination of normal paraffin content and carbon number distribution in liquid paraffin products and raw materials — Gas chromatography

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Card type: Test method

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

• Standard number: NB/SH/T 0889—2014
• Chinese name: Determination of normal paraffin content and carbon number distribution in liquid paraffin products and raw materials — Gas chromatography
• English name: Liquid paraffin wax and its raw oil—Determination of normal paraffin hydrocarbons content and carbon number distribution—Gas chromatography
• Replacement relationship: This standard is first published (no statement of replacing other standards is provided in the available source)
• Publication/implementation: 2014-06-29 published, 2014-11-01 implemented
• Publishing unit: National Energy Administration
• Custodian: National Technical Committee for Standardization of Petroleum Products and Lubricants, Subcommittee on Petroleum Wax Products (SAC/TC280/SC3)
• Drafting unit: Fushun Research Institute of Petroleum and Petrochemicals, China Petroleum & Chemical Corporation
• Drafters: Cheng Zhongqian, Ling Fengxiang, Taishi Jianyao

2. Scope of application and non-applicability

• 1.1 This standard specifies a test method for determining the normal paraffin content and carbon number distribution in liquid paraffin products and raw materials by gas chromatography.
• 1.2 This standard applies to the determination of normal paraffin content and carbon number distribution in liquid paraffin products and raw materials.
• Not applicable: not provided in the available source.
• Warning: This standard may involve certain hazardous materials, equipment, and operations, but it is not intended to address all safety issues associated with them. Before use, users are responsible for establishing appropriate safety and protective measures and determining the applicability of relevant regulations.

3. Method principle

Inject the sample into a gas chromatograph. The vaporized sample is separated in the chromatographic column according to boiling point and then enters a flame ionization detector for detection. After the detected signal is processed by baseline maintenance integration and valley-to-valley integration, the normal paraffin content and carbon number distribution are obtained.

4. Reagents and materials (purity / preparation)

• 4.1 nC5~nC22: purity greater than 99.0%. (Original text is “nCs~nCz”, requires confirmation against the source standard (source-text extraction))
• 4.2 Cyclohexane: analytical reagent. (Original text has a garbled spelling of cyclohexane, requires confirmation against the source standard (source-text extraction))
• 4.3 Carrier gas: helium or hydrogen, generally purity not lower than 99.99%. (Original text “helium”, source-text extraction writes “ammonia”, requires confirmation against the source standard (source-text extraction))
• 4.4 Auxiliary gases:
  • Hydrogen: purity greater than 99.99%;
  • Air: dehydrated, hydrocarbon-free.
• 7.1 Preparation of normal paraffin standard solution: select even-carbon-number normal paraffins in the range nC5~nC22, dissolve them in cyclohexane solvent to prepare a normal paraffin standard solution. The amounts of normal paraffins added are approximately equal, with a concentration of about 3% (mass fraction). (Original text “nCs~nC.oz”, requires confirmation against the source standard (source-text extraction))

5. Instruments and equipment

• 5.1 Gas chromatograph with the following configuration:
  • 5.1.1 Column oven: control precision of set temperature ±0.5℃. (Original text “[unreadable sign]0.5°”, requires confirmation against the source standard (source-text extraction))
  • 5.1.2 Inlet: split/splitless inlet.
  • 5.1.3 Flame ionization detector (FID) and signal conversion/amplification system:
    • Minimum detector response (S) greater than 0.08 pA·s/ng (nC16) (Original text “nC.1o”, requires confirmation against the source standard (source-text extraction))
    • Linear range greater than 10^7 (Original text “10’”, requires confirmation against the source standard (source-text extraction))
  • 5.1.4 Data processing system: chromatography workstation.
  • 5.1.5 Capillary chromatographic column: methyl cross-linked siloxane chromatographic column, 50 m × 0.20 mm × 0.50 μm. (Original text “0.50wm”, requires confirmation against the source standard (source-text extraction))
  • 5.1.6 Flow controller: flow variation less than 0.05 mL/min.
• 5.2 Syringe: 1.0 μL. (Original text “1.0wL”, requires confirmation against the source standard (source-text extraction))

6. Recommended operating conditions

Table 1 Chromatographic operating conditions (original text Table 1)

• 7.2 Column aging: connect the column to the inlet, set the carrier gas flow rate to 0.5 mL/min, and age the column at a column oven temperature of 310℃ for 30 min. Connect the outlet of the aged column to the inlet of the flame ionization detector, and leak-test the system until there is no leakage. Each time the instrument is used, the column should preferably be aged at the highest temperature used by the method for 10 min to ensure repeatability of analysis results. (Original text “310~”, requires confirmation against the source standard (source-text extraction))
• 7.4 Column resolution: prepare a cyclohexane solution of C8 and C9 normal paraffin samples to check the column efficiency. The concentrations of C8 and C9 are approximately equal, about 3% (mass fraction). The column resolution (R) calculated according to formula (1) is required to be not less than 30. (Original text “Cs and C,” “concentration of C [garbled]”, requires confirmation against the source standard (source-text extraction))

Formula (1): R = 2(tR C9 − tR C8) / [1.699(w C9 + w C8)]

Where:

• R—— column resolution;
• tR retention time of C8——nC8, min (retain three significant figures);
• tR retention time of C9——nC9, min (retain three significant figures);
• w half-peak width of C8——nC8, min (retain three significant figures);
• w half-peak width of C9——nC9, min (retain three significant figures). (Original formula symbols source-text extraction are severely noisy, requires confirmation against the source standard (source-text extraction))

7. Sampling and sample preparation

• 6 Sampling: sample according to GB/T 4756 Manual sampling of petroleum liquids.
• 7.1 Preparation of normal paraffin standard solution: see Section 4.
• 7.2 Column aging: see Section 6.
• 7.4 Column resolution test solution: see Section 6.
• 7.5.1 Standard sample for determining minimum detector response (S): prepare a standard sample in which the concentration of nC16 is in the range 1.80 ng/μL~2.20 ng/μL. (Original text “nC.,.” “ng/ML~2.20[unreadable character]g/[unreadable character]”, requires confirmation against the source standard (source-text extraction))

8. Analysis procedure

• 9.1 Set instrument parameters according to the chromatographic operating conditions in Table 1.
• 9.2 Take 0.2 μL sample and inject into the gas chromatograph. A typical chromatogram is shown in Figure 1.
• 9.3 Integrate the stored detection signal using the following integration modes.
  • 9.3.1 Integrate the detection signal using valley-to-valley integration, as shown in Figure 2, to obtain the area A of each normal paraffin chromatographic peak in the chromatogram. (Original text Figure 2 and Figure 3 labels are suspected to be interchanged, requires confirmation against the source standard (source-text extraction))
  • 9.3.2 Integrate the detection signal using baseline maintenance integration, as shown in Figure 3, to obtain the total area A of all chromatographic peaks.
• 8 Normal paraffin qualitative analysis: run the 7.1 normal paraffin standard solution under the chromatographic operating conditions in Table 1, and determine the retention time of each normal paraffin from nC8~nC22. Repeat the analysis 5 times; the retention time repeatability of repeated analyses must be less than 0.10 min.
• 7.5 Determination of minimum detector response (S):
  • 7.5.2 Run the standard sample 11 times under the operating conditions in Table 1 to obtain the peak area A of nC16.
  • 7.5.3 Calculate the minimum detector response (S) according to formula (2).

Formula (2): S = A / (C16 × V)

Where:

• S—— minimum detector response, pA·s/ng (nC16);
• A—— average value of the peak areas of nC16 measured 11 times, pA·s;
• concentration of C16——nC16, ng/μL;
• V—— injection volume, μL. (Original formula source-text extraction is written as “S-G.X”, requires confirmation against the source standard (source-text extraction))

9. Qualitative and quantitative analysis and calculation formulas

• 10.1 The mass fraction of each normal paraffin (Ci) is calculated using formula (3):

Formula (3): Ci = (Ai / A) × 100

Where:

• Ci—— mass fraction of the normal paraffin with carbon number i, % (mass fraction);

• Ai—— area of the normal paraffin with carbon number i, pA·s;

• A—— total area of all chromatographic peaks, pA·s.

• 10.2 The total normal paraffin content is calculated using formula (4):

Formula (4): C = ΣCi

Where:

• Ci—— mass fraction of normal alkanes with carbon number i, % (mass fraction);
• C—— total mass fraction of normal alkanes, % (mass fraction).

10. Precision

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

12.1 Repeatability (r): the difference between two consecutive determination results on the same sample by the same laboratory, the same operator, using the same instrument and equipment, under the same experimental conditions shall not exceed the following values.

• r(C13~C15) = 0.012 × X^0.701 + 0.01 (original text "Ta-OIs = 0.012 × X701+0.01", requires confirmation against the source standard (source-text extraction))
• r(C14~C22) = 0.025 × X^0.739 + 0.01 (original text "C14-C22 = 0.025 × X0.739 +0.01", requires confirmation against the source standard (source-text extraction))
• r total = 1.20% (mass fraction)

Where: X—— average of two determination results, % (mass fraction).

12.2 Bias: because there is no acceptable reference standard material, the bias of these steps cannot be determined.

11. Report

Report the mass fraction of each normal alkane and the total mass fraction of normal alkanes in the sample, accurate to 0.01% (mass fraction).

12. Referenced documents

• GB/T 4756 Petroleum liquids—Manual sampling (GB/T 4756—1998, eqv. ISO 3710:1998)
• GB/T 1.1—2009 (mentioned in the foreword, this standard was drafted according to the rules given therein)

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