⛽ Benzene content in gasoline
Determination of benzene content in unleaded gasoline by gas chromatography with FID detection. Key quality and environmental parameter of motor fuels.
Overview
Benzene (C₆H₆) is an aromatic hydrocarbon naturally occurring in crude oil and its refining products. It is a component of motor gasoline affecting octane number, however due to strong carcinogenic properties (IARC group 1 — leukemia) its content in gasolines is strictly legally regulated. Directive 2009/30/EC (Fuel Quality Directive) and Polish Regulation limit maximum benzene content in gasoline to 1.0% v/v.
PN-EN 12177 method consists of separation of gasoline components by gas chromatography (GC) technique using capillary column with high selectivity toward aromatic hydrocarbons. Benzene is identified based on retention time and quantified using internal standard or external calibration method with flame ionization detection (FID).
The test is mandatory in fuel quality monitoring system in Poland (URE, UOKiK) and routinely performed by refinery laboratories (PKN Orlen, Lotos/Aramco), Trade Inspection and accredited testing laboratories. Every gasoline batch entering the market must meet the criterion ≤1.0% v/v benzene.
Method principle
Gasoline sample is introduced into gas chromatograph equipped with capillary column with stationary phase of high selectivity toward aromatic hydrocarbons (e.g. 100% dimethylpolysiloxane or polar phase). In carrier gas stream (helium or nitrogen) sample components separate on column according to boiling points and interactions with stationary phase. Benzene, eluting as separate peak, is detected by flame ionization detector (FID). Quantitative determination is based on comparison of benzene peak area with internal standard peak area (e.g. fluorobenzene) or calibration curve prepared from benzene standard solutions in isooctane.
Applications
- Quality control of motor gasolines at fuel stations (Trade Inspection)
- Production quality monitoring in refineries (PKN Orlen, Lotos)
- Compliance testing with Fuel Directive 2009/30/EC
- Control of imported fuels (Customs Service)
- Assessment of benzene emissions from motor vehicles
- Testing of reformulated and ethanol fuels (E5, E10)
Key parameters
| Parameter | Value |
|---|---|
| Determination range | 0.1–5.0% v/v benzene |
| Legal limit (Directive 2009/30/EC) | ≤1.0% v/v |
| Repeatability | 0.06–0.10% v/v (depending on concentration) |
| Reproducibility | 0.12–0.20% v/v |
| Detection | FID (flame ionization) |
| Carrier gas | Helium or nitrogen, flow 1–2 mL/min |
Standard
- Standard number
- PN-EN 12177:2010
- Title (PL)
- Ciekłe przetwory naftowe — Benzyna bezołowiowa — Oznaczanie zawartości benzenu metodą chromatografii gazowej
- Title (EN)
- Liquid petroleum products — Unleaded petrol — Determination of benzene content by gas chromatography
Step-by-step procedure
1. Preparation of standard solutions
Prepare series of benzene solutions in isooctane at concentrations 0.1; 0.5; 1.0; 2.0; 5.0% v/v. Add internal standard (fluorobenzene) at constant concentration 0.5% v/v.
2. GC configuration
Set parameters: DB-1 60 m column, He carrier gas 1.5 mL/min, inlet 250°C split 1:100, oven temp. program: 35°C (10 min) → 2°C/min → 60°C → 5°C/min → 200°C.
3. FID detector calibration
Set FID: temp. 300°C, H₂ 40 mL/min, air 400 mL/min, make-up N₂ 25 mL/min. Ignite flame. Check baseline (stability, noise).
4. Analysis of calibration solutions
Inject 0.2–1.0 µL of each standard solution (from lowest concentration). Perform 2 replicates each. Build calibration curve (peak area vs concentration).
5. Gasoline sample preparation
Measure 1 mL gasoline sample into GC vial. Add internal standard (fluorobenzene). Close with PTFE/silicone septum cap. Mix.
6. Chromatographic analysis of sample
Inject sample in split mode (1:100). Record chromatogram. Analysis time ~40–60 min. Identify benzene peak based on retention time.
7. Integration and calculations
Integrate benzene and internal standard peaks. Calculate benzene content from calibration curve. Result in % v/v with accuracy to 0.01%.
8. Quality control (QC)
Analyze control sample (gasoline CRM) every 10 samples. Check agreement with certified value (±2σ). Monitor control charts.
9. Reporting
Result: "Benzene content = X.XX % v/v". Compare with limit 1.0% v/v. Attach chromatogram and calibration data.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Gas chromatograph with FID | Agilent 8890, Shimadzu GC-2030, Thermo TRACE 1310 | 120,000–300,000 PLN |
| Capillary column | Agilent DB-1 60 m × 0.25 mm × 1.0 µm or HP-PONA | 2,000–5,000 PLN |
| Autosampler | Agilent 7693A, Shimadzu AOC-20i | 40,000–80,000 PLN |
| Hydrogen and air generator for FID | Peak Scientific Precision, Parker Balston | 15,000–35,000 PLN |
| Microsyringe 1–10 µL | Hamilton 701N, SGE 10 µL | 300–800 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Benzene — certified standard | 71-43-2 | Purity ≥99.9%, GC calibration standard, 1 mL ampoules, Sigma-Aldrich/Merck |
| Isooctane (2,2,4-trimethylpentane) | 540-84-1 | Solvent for preparation of standard solutions, GC grade purity ≥99.5% |
| Fluorobenzene (internal standard) | 462-06-6 | IS for internal standard method, purity ≥99% |
| Toluene — retention standard | 108-88-3 | Identification control, GC grade purity |
| Helium as carrier gas | 7440-59-7 | Purity ≥99.999% (5.0), 50 L / 200 bar cylinder |
Health and safety (OHS)
- Benzene — carcinogenic (cat. 1A, R45/H350)! Work only under fume hood, nitrile gloves, goggles
- Gasoline — flammable (R11/H224), vapors form explosive mixtures with air
- Isooctane — flammable, store away from ignition sources
- Helium/hydrogen — gases under pressure, hydrogen explosive — installation tightness control
- Benzene-containing waste — disposal as hazardous waste (code 16 05 06*)