⛽ Benzene content in gasoline

Petrochemistry PN-EN 12177

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

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.

   ⏱ Time: 20 min

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.

   ⏱ Time: 10 min

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).

   ⏱ Time: 15 min

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).

   ⏱ Time: 60 min

5. Gasoline sample preparation

   Measure 1 mL gasoline sample into GC vial. Add internal standard (fluorobenzene). Close with PTFE/silicone septum cap. Mix.

   ⏱ Time: 5 min

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.

   ⏱ Time: 40–60 min

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%.

   ⏱ Time: 5 min

8. Quality control (QC)

   Analyze control sample (gasoline CRM) every 10 samples. Check agreement with certified value (±2σ). Monitor control charts.

   ⏱ Time: 40 min

9. Reporting

   Result: "Benzene content = X.XX % v/v". Compare with limit 1.0% v/v. Attach chromatogram and calibration data.

   ⏱ Time: 10 min

Required equipment and apparatus

Reagents, media and consumables

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*)

Frequently asked questions