GB/T 3144-1982 Determination of hydrocarbon impurities in toluene by gas chromatography

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Card type: Test method

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

• Standard number: GB 3144-82
• Chinese name: Determination of hydrocarbon impurities in toluene by gas chromatography
• English name: Toluene-determination of hydrocarbon impurities—gas chromatographic method
• UDC: 668.735.2 : 543.541
• Replacement relationship: not provided in the available source
• Reference relationship: This standard was formulated with reference to ISO 5279
• Issued/implemented: issued by the National Bureau of Standards on 1982-07-20, implemented on 1983-03-01

2. Scope of application and non-applicability

• Applicable to the determination of hydrocarbon impurities in toluene.
• Impurities include: benzene, C8 aromatics, and non-aromatics up to n-nonane.
• The measurement range for each group of impurities is 0.01~1.00% (mass ratio).
• Not applicable: not provided in the available source.

3. Method principle

Add a known amount of internal standard to the sample, use a syringe to take a certain amount of this mixture and inject it into the vaporization chamber of the chromatograph. The vaporized mixture is carried by the carrier gas into the chromatographic column. Each component flowing out is detected by a flame ionization detector, and the chromatogram is recorded on a recorder. The relative retention time of the impurities is used for qualitative identification, and the peak areas of the impurities relative to the internal standard are used for quantification. The relative correction factors of the detector for each component must be considered during calculation.

4. Reagents and materials (purity / preparation)

• 3.1 n-Hexane: chromatographic grade (does not contain benzene, n-decane, or ethylbenzene).
• 3.2 Internal standard: n-decane, purity not less than 99% (mass ratio).
• 3.3 Reference materials: purity not less than 99% (mass ratio).
  • 3.3.1 Benzene
  • 3.3.2 Toluene
  • 3.3.3 Ethylbenzene
  • 3.3.4 n-Undecane (original text reads “n-undecane” [garbled], requires confirmation against the source standard (source-text extraction))
• 3.4 Stationary phase
  • 3.4.1 Poly C- glycol 1500 (original text reads “polyC- glycol1500”, requires confirmation against the source standard (source-text extraction))
  • 3.4.2 6201 support (60–80 mesh) (original text reads “60–80 mesh” [garbled], requires confirmation against the source standard (source-text extraction))
• 2.2 Materials
  • 2.2.1 Stoppered volumetric flask: 10 mL
  • 2.2.2 Hydrogen: oxygen content not higher than 0.0005% (volume ratio)
  • 2.2.3 Nitrogen
  • 2.2.4 Compressed air
  • 2.2.5 Oxygen regulator
  • 2.2.6 Standard sieve: 60 mesh and 80 mesh
• Stationary phase preparation (4.1): Weigh 12.3 g of poly glycol 1500 (original text has a missing character, requires confirmation against the source standard (source-text extraction)), dissolve in 50 mL of a suitable solvent (such as methanol). Pour the solution into 37.5 g of 6201 support and stir gently. Use an infrared lamp to bake slowly and evaporate the solvent until the solvent is completely evaporated. If the coated stationary phase has powder, it may be sieved again to improve column efficiency.

5. Instruments and equipment

• 2.1.1 Chromatograph: any model of chromatograph with a flame ionization detector that can meet the requirements of the test conditions. The instrument should have sufficient sensitivity; for a mixture containing 0.005% (mass ratio) ethylbenzene, under the specified test conditions, the resulting peak height should be at least twice the noise (original text reads “noise” [garbled], requires confirmation against the source standard (source-text extraction)).
• 2.1.2 Analytical balance: sensitivity 1/1000 g.
• 2.1.3 Syringes: 1 μL, 10 μL, 50 μL, 10 mL, and 50 mL.
• 2.1.4 Chromatographic column: made of stainless steel tube, copper tube, aluminum tube, or glass tube, length 4 m, inner diameter 2 mm.

6. Recommended operating conditions

Table 3 Test conditions:

• Column temperature: 100℃ (allowed to adjust up or down by 20℃)
• Vaporization temperature: 180℃ (not lower than the boiling point of the heaviest component)
• Carrier gas (H2) flow rate: adjust so that the retention time of toluene is 6~10 minutes (not exceeding 15 minutes)
• Air flow rate: adjust according to the requirements of the flame ionization detector of different instruments. Usually the ratio to carrier gas is carrier gas:air = 1:10~15
• Makeup gas (N2) flow rate: ratio to carrier gas flow rate is 1:1
• Injection volume: 1 μL (provided separation is satisfactory, the injection volume may also be increased)
• Paper speed: 300 mm/h

7. Sampling and sample preparation

• 5.2 Respectively take 20 μL of n-decane and 10 mL of sample and inject into a stoppered volumetric flask. Weigh out the masses of n-decane and sample by the incremental method. Weigh to the nearest 0.2 mg.
• 4.4.1 Use a syringe to take 10 mL of n-hexane and inject into a clean, dry, stoppered 10 mL volumetric flask. Use a 50 μL syringe to respectively inject 50 μL each of n-decane, benzene, toluene, and ethylbenzene into the volumetric flask in sequence. Weigh out the mass of each component by the incremental method, weighing to the nearest 0.2 mg.
• 4.5.1 Use a syringe to take 10 mL of n-hexane and inject into a clean, dry, stoppered 10 mL volumetric flask. Use a 50 μL syringe to respectively inject 50 μL each of n-nonane, benzene, n-decane, toluene, n-undecane, ethylbenzene, m-xylene, p-xylene, and o-xylene into the volumetric flask in sequence, and mix uniformly.

8. Analytical procedure

• 4.2 Packing and aging of the chromatographic column: Plug one end of the chromatographic column with porous metal mesh or glass wool, and connect it to a vacuum pump. Connect the other end to a funnel, and load the prepared stationary phase into the chromatographic column through the funnel. While packing the column, tap or vibrate the column while drawing air to ensure uniform packing. When the column is filled, remove the chromatographic column and stop the pump. Pour out a small amount of stationary phase, then plug this end with porous metal mesh or glass wool. Install the chromatographic column on the chromatograph. After checking for leaks, age it by passing carrier gas at a temperature 20~50℃ higher than the operating temperature until the baseline is stable.
• 4.3 Chromatographic column performance check
  • 4.3.1 Under the specified test conditions, the chromatographic column should be able to completely separate the internal standard from all other components.
  • 4.3.2 Prepare a toluene mixture containing 0.10% (volume ratio) ethylbenzene (original text has a missing character, requires confirmation against the source standard (source-text extraction)). Take 1 μL of this mixture, inject into the vaporization chamber of the chromatograph, and record the chromatogram. Measure the heights from the valley between the toluene and ethylbenzene peaks to the baseline. The heights from the valley between the two peaks to the baseline should not exceed 10% of the ethylbenzene peak height.
• 4.4 Determination of correction factors
  • 4.4.2 According to the test conditions specified in Table 3, after the instrument is stable, inject the above standard sample into the chromatograph and record the chromatogram.
• 4.5 Determination of relative retention times
  • 4.5.2 Under the test conditions specified in Table 3, after the instrument is stable, inject the above standard sample into the chromatograph and record the retention time of each component. Using n-undecane as the reference, calculate the relative retention time of each component. Use these relative retention times for qualitative identification.
• 5.1 Adjust the instrument according to the test conditions specified in Table 3.
• 5.3 Under the test conditions specified in Table 3, after the chromatograph is stable, inject 1 μL of the prepared sample and record the chromatogram (typical chromatogram).
• 5.4 Measure the peak areas of each impurity and n-decane (internal standard). When measuring manually, measure the peak height and half-peak width. The peak area is obtained by multiplying the peak height by the half-peak width. If a data processor is used, analysis and calculation programs may be pre-programmed for automatic calculation.

9. Qualitative and quantitative determination and calculation formulas

• Qualitative: use relative retention time for qualitative identification (with n-undecane as the reference).
• Table 2 Typical relative retention times of each component:
  • n-Nonane: 0.30
  • Benzene: 0.42
  • n-Decane: 0.54
  • Toluene: 0.75
  • n-Undecane: 1.00
  • Ethylbenzene: 1.26
  • m-Xylene, p-Xylene: 1.37
  • o-Xylene: 1.79
• Calculation of relative correction factor (Formula 1): F_i = (A_i · M_L) / (M_i · A_L) Where: F_i— relative correction factor of the component; A_i—i peak area of the component; A_L— peak area of n-decane; M_i—i mass of the component, g; M_L— mass of n-decane, g.
• Table 1 Typical correction factors:
  • n-Decane: 1.00
  • Benzene: 1.17
  • Toluene: 1.10
  • Ethylbenzene: 1.02 (original text reads “102”, requires confirmation against the source standard (source-text extraction))
• If the difference between the relative correction factor obtained by the above test procedure and the typical correction factor given in Table 1 exceeds 10% of the given value, it must be checked again with a second standard sample until the difference between the two values is less than 10%; only then may the measured value be used.
• Quantitative calculation (Formula 2): X_i = 100 × (A_i · M_L · F_L) / (A_L · M_O · F_i) Where: X_i— mass percentage of the component in the sample; A_i—i peak area of the component; A_L— peak area of n-decane (internal standard); F_i—i relative correction factor of the component; F_L— relative correction factor of n-decane; M_O— mass of the sample, g; M_L— mass of n-decane (internal standard) used, g.
• Note: All non-aromatics use the same relative correction factor as n-decane. All C8 aromatics use the same relative correction factor as benzene (original text reads “C* aromatics” “benzene benzene”, requires confirmation against the source standard (source-text extraction)).
• Impurity content is expressed as mass percentage. According to reporting requirements, calculate the content of each group of benzene, non-aromatics, and C8 aromatics to 0.01%.

10. Precision

Use the following values to judge the reliability of the results (95% confidence level).

• 7.1 Repeatability: For the same operator, the difference between two repeated determination results shall not exceed the following: when the impurity content is in the range 0.01–0.10%, it is 0.01% (mass ratio); when the impurity content is in the range 0.10–1.00%, it is 10% of the arithmetic mean.
• 7.2 Reproducibility: The difference between the determination results of the same sample by two laboratories shall not exceed the following: when the impurity content is in the range 0.01–0.10%, it is 0.02% (mass ratio); when the impurity content is in the range 0.10–1.00%, it is 20% of the arithmetic mean.

11. Report

Take the arithmetic mean of two parallel determination results as the determination result of hydrocarbon impurities in the sample, and report the result to 0.01% (mass ratio).

12. Reference documents

• ISO 5279 (reference formulation)
• No other normative reference documents are provided in the available source.

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