⛽ Sulfur Content in Fuels
In short
Determination of sulfur content in automotive fuels in range 3–500 mg/kg by UV fluorescence method after combustion of sample in oxygen-rich atmosphere. The test is performed according to PN-EN ISO 20846:2019; Measurement range: 3–500 mg/kg (fuels), 3–45 mg/kg (synthetic fuels). The procedure comprises 10 steps (about 1 h 19 min–1 h 51 min in total); it is used for: Quality control of diesel (PN-EN 590: max 10 mg/kg sulfur), Quality control of motor gasolines (PN-EN 228: max 10 mg/kg), Testing of jet fuel Jet A-1.
At a glance
- Standard: PN-EN ISO 20846:2019
- Category: Petrochemistry
- Procedure steps: 10
- Total time of stages: 1 h 19 min–1 h 51 min
- Measurement range: 3–500 mg/kg (fuels), 3–45 mg/kg (synthetic fuels)
- Limit of quantitation: ~1 mg/kg (instrument dependent)
- Repeatability (10 mg/kg): ±1.5 mg/kg
Overview
Sulfur in fuels is one of the most rigorously controlled parameters due to its negative environmental impact (SO₂ emissions, acid rain) and durability of emission control systems (poisoning of three-way catalyst and diesel particulate filter DPF). EU requirements limit sulfur content in gasoline and diesel to maximum 10 mg/kg (10 ppm) — so-called sulfur-free fuels.
The ultraviolet (UV) fluorescence method involves combustion of fuel sample in high-temperature furnace (1000–1100°C) in oxygen-rich atmosphere, causing conversion of all sulfur compounds to sulfur dioxide (SO₂). SO₂ gas is then excited by UV radiation and emits characteristic fluorescence whose intensity is proportional to SO₂ concentration, and thus to sulfur content in sample.
The method is applied to motor gasolines (including those containing up to 10% ethanol), diesel oils (including with up to 30% FAME addition), and synthetic fuels (HVO, GTL). Measurement range covers from 3 to 500 mg/kg sulfur. Potential interferences are halogens (above 3500 mg/kg) and nitrogen from cetane improvers.
Test result is required in every fuel quality certificate according to PN-EN 590 (diesel) and PN-EN 228 (gasoline). It is also crucial for marine fuels (IMO 2020 sulfur directive) and aviation fuels. Fuel laboratories perform this determination routinely with every fuel batch.
Method principle
Fuel sample is introduced (directly or after dilution) into combustion furnace at 1000–1100°C in argon/oxygen stream. Sulfur compounds present in sample are oxidized to SO₂. Combustion gases are dried and delivered to UV detection chamber. UV radiation at wavelength approx. 220 nm excites SO₂ molecules which emit fluorescence in 300–400 nm range. Fluorescence intensity is proportional to SO₂ concentration (Beer-Lambert law). Signal is recorded by photomultiplier and converted to sulfur content based on calibration curve prepared from certified standards.
Applications
- Quality control of diesel (PN-EN 590: max 10 mg/kg sulfur)
- Quality control of motor gasolines (PN-EN 228: max 10 mg/kg)
- Testing of jet fuel Jet A-1
- Control of marine fuels (IMO 2020: max 0.50% m/m)
- Testing of biofuels — FAME, HVO, GTL
- Monitoring desulfurization processes in refineries (HDS)
- Control of petrochemical feedstocks
Key parameters
| Parameter | Value |
|---|---|
| Measurement range | 3–500 mg/kg (fuels), 3–45 mg/kg (synthetic fuels) |
| Limit of quantitation | ~1 mg/kg (instrument dependent) |
| Repeatability (10 mg/kg) | ±1.5 mg/kg |
| Reproducibility (10 mg/kg) | ±3.4 mg/kg |
| Combustion temperature | 1000–1100°C |
| Sample volume | 5–20 µL (direct injection) |
Standard
- Standard number
- PN-EN ISO 20846:2019
- Title (PL)
- Przetwory naftowe — Oznaczanie zawartości siarki w paliwach samochodowych — Metoda fluorescencji w nadfiolecie
- Title (EN)
- Petroleum products — Determination of sulfur content of automotive fuels — Ultraviolet fluorescence method
Step-by-step procedure
-
Analyzer startup
Turn on analyzer, open gas cylinder valves (Ar, O₂). Heat furnace to operating temperature 1050°C. Stabilize UV detector baseline.
-
Calibration
Prepare calibration curve from minimum 3–5 standards (e.g., 0, 5, 10, 50, 100 mg/kg S). Correlation coefficient R² ≥ 0.999.
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Sample preparation
Mix fuel sample thoroughly. For samples with high S content — dilute with isooctane. Record sample mass.
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Blank measurement
Perform blank measurement (pure isooctane or clean boat) to determine background and potential contamination.
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Sample introduction
Use microsyringe to withdraw 5–20 µL sample and inject onto ceramic boat or directly into furnace (depending on instrument).
-
Combustion and detection
Sample combusted at 1050°C in O₂/Ar atmosphere. SO₂ transported to UV chamber, fluorescence signal recorded. Analysis time per sample approx. 3–5 min.
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Result readout
Software automatically calculates sulfur content based on calibration curve and sample mass. Result in mg/kg.
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Repeat and QC
Perform minimum 2 determinations. Every 10 samples measure control sample (CRM). CRM result must be within certified uncertainty limits.
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Blank verification
After sample series perform blank — check for memory effect (carry-over) from high sulfur samples.
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Instrument shutdown
After work completion: cool down furnace, close gas cylinders, clean gas path. Record gas and boat consumption.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| UV fluorescence sulfur analyzer | Analytik Jena multi EA 5100, Mitsubishi TS-100V | 120 000–250 000 PLN |
| Compact analyzer | Analytik Jena compEAct, HORIBA SLFA-60 | 80 000–150 000 PLN |
| Autosampler | Automatic sample feeder 50–100 positions | 30 000–60 000 PLN |
| Ceramic/quartz boats | Combustion boats, disposable or reusable | 5–20 PLN/pc (ceramic) |
| Gas cylinders (Ar, O₂) | Argon 5.0 (50 L), Oxygen 5.0 (50 L) with regulators | 500–1 200 PLN/cylinder |
| Microsyringe | Hamilton 10–50 µL for dosing liquid samples | 400–1 200 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Sulfur standards in base oil | — | Certified CRM standards: 5, 10, 20, 50, 100, 500 mg/kg S in isoparaffinic oil, e.g., AccuStandard, Conostan |
| Isooctane (solvent/diluent) | 540-84-1 | Purity ≥99.5%, ultra-low sulfur content (<0.5 mg/kg), for diluting samples |
| Toluene (low-sulfur) | 108-88-3 | Spectroscopic purity, S content <1 mg/kg, for cleaning and dilution |
| Dibenzothiophene (single compound standard) | 132-65-0 | Purity ≥99%, for preparing working standard solutions |
| Argon 5.0 | 7440-37-1 | Carrier gas, purity ≥99.999% |
| Oxygen 5.0 | 7782-44-7 | Combustion gas, purity ≥99.999% |
Health and safety (OHS)
- Fuels — flammable and volatile, work in well-ventilated area
- Combustion furnace 1050°C — risk of burns, do not touch hot elements
- Gas cylinders under pressure — secure against tipping, check tightness
- Isooctane — flammable and irritating, work in fume hood
- Safety glasses, nitrile gloves, laboratory coat mandatory
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 20846:2019 — “Petroleum products — Determination of sulfur content of automotive fuels — Ultraviolet fluorescence method”.
How does this method work?
Fuel sample is introduced (directly or after dilution) into combustion furnace at 1000–1100°C in argon/oxygen stream. Sulfur compounds present in sample are oxidized to SO₂.
What is the measuring range and accuracy?
Measurement range: 3–500 mg/kg (fuels), 3–45 mg/kg (synthetic fuels); Limit of quantitation: ~1 mg/kg (instrument dependent); Repeatability (10 mg/kg): ±1.5 mg/kg; Reproducibility (10 mg/kg): ±3.4 mg/kg.
How long does the test take?
The times given for the individual stages add up to approximately 1 h 19 min–1 h 51 min. The procedure comprises 10 steps.
What equipment is required?
UV fluorescence sulfur analyzer, Compact analyzer, Autosampler, Ceramic/quartz boats, Gas cylinders (Ar, O₂), Microsyringe. Indicative cost of the core instrument (UV fluorescence sulfur analyzer): 120 000–250 000 PLN.
Where is this test used?
Quality control of diesel (PN-EN 590: max 10 mg/kg sulfur); Quality control of motor gasolines (PN-EN 228: max 10 mg/kg); Testing of jet fuel Jet A-1; Control of marine fuels (IMO 2020: max 0.50% m/m); Testing of biofuels — FAME, HVO, GTL; Monitoring desulfurization processes in refineries (HDS); Control of petrochemical feedstocks.
What safety precautions apply?
Fuels — flammable and volatile, work in well-ventilated area; Combustion furnace 1050°C — risk of burns, do not touch hot elements; Gas cylinders under pressure — secure against tipping, check tightness; Isooctane — flammable and irritating, work in fume hood; Safety glasses, nitrile gloves, laboratory coat mandatory.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 20846.