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

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.

Keywords: BTEX compounds, gas chromatograph, FID detector, ambient air.

1. Experiment Method

1.1 Instrument Configuration

Table 1 Configuration List of Gas Chromatograph

1.2 Experimental Materials and Auxiliary Equipment

Standard stock solution of 8 benzene series compounds in carbon disulfide(100μg/mL)

Carbon disulfide: GC grade

Nitrogen

Hydrogen generator

Air generator

1.3 Test Conditions

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

1.4 Solution Preparation

1.4.1 Linear Standard Working Solutions for Benzene Series Compounds

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.

1.4.2 LOD Solution of Benzene Series Compounds (0.1μg/mL)

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.

2. Result and Discussion

2.1 Standard Sample Qualitative Analysis

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)

Note: As shown in the above chromatogram, the resolution of the chromatographic peaks of each benzene compound is greater than 1.5, which meets the requirements of experimental analysis.

2.2 Repeatability

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

Table 3 Chromatographic Repeatability Parameters for Benzene

No.	Component	Retention Time	Peak Area
1	Benzene	3.121	32.320
2		3.121	32.395
3		3.123	32.715
4		3.123	32.244
5		3.122	32.180
6		3.123	32.558
Average	N/A	3.122	32.402
RSD (%)	N/A	0.031	0.622

Table 4 Chromatographic Repeatability Parameters for Toluene

No.	Component	Retention Time	Peak Area
1	Toluene	5.171	34.269
2		5.170	34.237
3		5.172	34.647
4		5.172	34.225
5		5.170	34.178
6		5.173	34.513
Average	N/A	5.171	34.345
RSD (%)	N/A	0.023	0.551

Table 5 Chromatographic Repeatability Parameters for Ethylbenzene

No.	Component	Retention Time	Peak Area
1	Ethylbenzene	7.755	34.984
2		7.756	34.960
3		7.756	35.422
4		7.757	34.936
5		7.756	34.761
6		7.756	35.345
Average	N/A	7.756	35.068
RSD (%)	N/A	0.008	0.735

Table 6 Chromatographic Repeatability Parameters for p-Xylene

No.	Component	Retention Time	Peak Area
1	p-Xylene	7.981	34.849
2		7.980	34.898
3		7.980	35.271
4		7.981	34.845
5		7.980	34.700
6		7.981	35.356
Average	N/A	7.980	34.970
RSD (%)	N/A	0.007	0.687

Table 7 Chromatographic Repeatability Parameters for m-Xylene

No.	Component	Retention Time	Peak Area
1	m-Xylene	8.183	35.231
2		8.182	35.284
3		8.184	35.731
4		8.183	35.270
5		8.183	35.218
6		8.184	35.682
Average	N/A	8.183	35.403
RSD (%)	N/A	0.009	0.670

Table 8 Chromatographic Repeatability Parameters for Isopropylbenzene

No.	Component	Retention Time	Peak Area
1	Isopropylbenzene	9.213	35.047
2		9.214	35.062
3		9.215	35.517
4		9.215	34.978
5		9.213	34.860
6		9.214	35.397
Average	N/A	9.214	35.143
RSD (%)	N/A	0.010	0.728

Table 9 Chromatographic Repeatability Parameters for o-Xylene

No.	Component	Retention Time	Peak Area
1	o-Xylene	9.527	35.342
2		9.527	35.329
3		9.529	35.769
4		9.527	35.251
5		9.526	35.112
6		9.527	35.658
Average	N/A	9.527	35.410
RSD (%)	N/A	0.010	0.710

Table 10 Chromatographic Repeatability Parameters for Styrene

No.	Component	Retention Time	Peak Area
1	Styrene	11.782	35.182
2		11.783	35.346
3		11.783	35.659
4		11.783	35.091
5		11.782	35.147
6		11.782	35.553
Average	N/A	11.782	35.330
RSD (%)	N/A	0.005	0.659

Note: The benzene series standard solution (10μg/mL) was injected six times repeatedly. The RSD values of retention time for all target compounds were less than 0.040%, and the RSD values of peak areas were all below 0.74%, demonstrating excellent repeatability.

2.3 Linearity

Fig 4 Calibration Curve and Correlation Coefficients for Benzene Series Compounds

Note: The calibration standards for benzene series compounds in this test are 0μg/mL, 0.5μg/mL, 1.0μg/mL, 5μg/mL, 10μg/mL, 20μg/mL, and 50μg/mL. All target components in the benzene series standard solutions demonstrated excellent linearity, with correlation coefficients (R²) >0.999, fully meeting analytical requirements.

2.4 Detection Limit

Calculation formula:

ρ =(W-W₀)×V / V_nd

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

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