Determination of BTEX Compounds in Ambient Air by Using GC6100 Gas Chromatograph

BTEX compounds(or benzene homologues) refer to benzene and its derivatives, which mainly include aromatic organic compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX). These substances are widely exist in industrial production, vehicle exhaust, construction materials (e.g., paints, coatings, adhesives), and daily-use products. BTEX compounds are characterized by high volatility and significant toxicity. Notably, benzene has been classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC). Prolonged exposure may lead to hematopoietic disorders including aplastic anemia and leukemia, while also causing severe damage to the central nervous system, reproductive system, and fetal development. This experiment references "Determination of BTEX Compounds in Ambient Air by Activated Carbon Adsorption/Carbon Disulfide Desorption-Gas Chromatography" (HJ 584-2010), using Wayeal's GC6100 gas chromatograph equipped with an FID detector for the analysis of benzene series compounds in ambient air.

Table 1 Configuration List of Gas Chromatograph

• Standard stock solution of 8 benzene series compounds in carbon disulfide(100μg/mL)
• Carbon disulfide: GC grade
• Nitrogen
• Hydrogen generator
• Air generator

• Chromatographic Column: Wax Capillary GC Column, 30m×0.32mm×0.5μm
• Temperature Program: Initial column temperature: 50°C (hold for 5 min); Ramp rate: 5°C/min -> 90°C (hold for 1 min)
• Carrier Gas: High-purity nitrogen (N₂)
• Column flow rate: 3mL/min
• Inlet temperature: 250°C
• Detector temperature: 250°C
• Air flow rate: 300mL/min
• Hydrogen flow rate: 40mL/min
• Makeup gas flow rate: 25mL/min
• Injection volume: 1μL
• Injection mode: Split Injection, Split Ratio 5:1

Accurately pipette the benzene series standard stock solution (100μg/mL), and dilute with carbon disulfide to prepare standard working solutions with mass concentrations of 0.5μg/mL, 1.0μg/mL, 5μg/mL, 10μg/mL, 20μg/mL, and 50μg/mL, respectively.

Accurately pipette the benzene series standard solution (0.5μg/mL), dissolve and dilute with carbon disulfide to prepare the limit of detection (LOD) solution at a concentration of 0.1μg/mL.

Fig 1 Blank Chromatogram of Carbon Disulfide Reagent

Fig 2 Chromatogram of Benzene Series Standard Solution (10μg/mL)

Table 2 Chromatographic Parameters for Benzene Series Standard Solution (10μg/mL)

Fig 3 Repeatability Chromatogram of of Benzene Series Standard Solution (10μg/mL)

Table 3 Chromatographic Repeatability Parameters for Benzene

Table 4 Chromatographic Repeatability Parameters for Toluene

Fig 4 Calibration Curve and Correlation Coefficients for Benzene Series Compounds

Calculation formula:

ρ =(W-W0)×V / Vnd

ρ: Mass concentration of target compound in air, mg/m³.

W: Mass concentration in sample desorption solution (from calibration curve), μg/mL.

W₀: Mass concentration in blank desorption solution (from calibration curve), μg/mL.

V: Volume of desorption solution, mL.

Vₙd: Sampling volume at standard conditions (101.325 kPa, 273.15K), L.

Fig 5 Chromatogram of Benzene

The benzene series standard solution (0.1μg/mL) was injected eight times repeatedly, and the results were substituted into the formula for calculation. With a sampling volume of 10L, the detection limits (MDL) ranged from 0.86×10⁻³ to 1.35×10⁻³ mg/m³, and the lower limits of quantification (LLOQ) were 3.45×10⁻³ to 5.4×10⁻³ mg/m³, complying with standard requirements.

3. Conclusion

This method utilizes the Wayeal’s Gas Chromatograph GC6100 equipped with an FID detector for the analysis of benzene series compounds in ambient air. The experimental results show that the resolution of the chromatographic peaks of each benzene compound is greater than 1.5, which meets the experimental analysis requirements. The benzene compound standard solution (10μg/mL) was injected six times, and the RSD values of the retention times of each benzene compound were all less than 0.040%, while the RSD value of the peak area was 0.74%, indicating good repeatability. When the concentration of the benzene standard working curve is 0.5-50μg/mL, the linearity of each component in the benzene standard solution is good, with a linear correlation coefficient > 0.999, meeting the requirements of experimental analysis. The detection limit and lower limit of quantification results of this method are in compliance with the standard requirements, confirming its suitability for benzene series compounds analysis in ambient air.

4. Attention

The solvents and standard samples used in the experiment are toxic and harmful compounds. Their solution preparation and sample pretreatment should be carried out in a fume hood. When operating, laboratory protective equipment should be worn in accordance with regulations to avoid contact with skin and clothing.