ISO 20847:2004

Overview

ISO 20847:2004 specifies an energy-dispersive X‑ray fluorescence (EDXRF) test method for the determination of sulfur content in automotive fuels. The method targets motor gasolines (including those with up to 2.7 % m/m oxygen) and diesel fuels (including up to 5 % V/V FAME) with sulfur concentrations in the 30 mg/kg to 500 mg/kg range. The standard defines instrumentation, sample handling, calibration and quality control practices for reliable sulfur measurement by EDXRF. It also notes limitations (e.g., spectral overlap) that make the method inapplicable to certain leaded or element-contaminated products.

Key topics and technical requirements

• Principle: Measure sulfur K‑line characteristic X‑radiation from a liquid fuel test portion using EDXRF and compare net counts against a calibration curve.
• Scope limits: Applicable primarily to automotive fuels within 30–500 mg/kg sulfur; precision data are established only for these materials and range.
• Interferences: Not applicable to leaded gasolines, some lead‑replacement fuels (e.g., containing ~8–20 mg/kg K), or samples with Pb, Si, P, Ca, K or halides at >1/10 of the sulfur concentration due to spectral overlap.
• Instrument requirements:
  • EDXRF analyser with background subtraction and capability to measure sulfur at 50 mg/kg with ≤3% counting‑statistic RSD.
  • X‑ray source with significant flux above 2.5 keV; detector resolution ≤800 eV at 2.3 keV.
  • Removable sample cup (≥5 mm depth) with X‑ray‑transparent film (2–6 µm polyester preferred) and helium purge for stability.
  • Ability to measure scattered radiation (for matrix compensation) or multiple energy regions to correct background.
• Calibration and standards:
  • Use certified reference materials (CRMs) or primary standards prepared from known sulfur compounds.
  • Primary standards ~1 000 mg/kg and ~5 000 mg/kg; calibration points typically include 1 000, 500, 300, 100 and blank; for low sulfur (<100 mg/kg) include 50 and 25 mg/kg standards.
  • Matrix‑matching and use of diluent oil (white oil or matched solvents) recommended to reduce C:H and oxygen matrix effects.
• Sample handling: Follow ISO 3170 / ISO 3171 sampling guidance; refrigerate light fractions; use consistent film batches and disposable cups where possible.

Applications and users

ISO 20847:2004 is used by:

• Petroleum testing laboratories for fuel quality and regulatory compliance (sulfur specification in gasoline and diesel).
• Refineries and fuel blenders for process control and product release testing.
• Environmental and regulatory agencies monitoring sulfur emissions related to fuel quality.
• Instrument manufacturers and calibration service providers developing EDXRF methods and calibrations.

Keywords: ISO 20847:2004, sulfur content, automotive fuels, EDXRF, diesel, gasoline, FAME, calibration standards, fuel testing.

Related standards

• ISO 8754 (broader sulfur ranges in petroleum products)
• ISO 3170, ISO 3171 (sampling of petroleum liquids)