ISO 13032:2012

Overview

ISO 13032:2012 specifies an energy-dispersive X‑ray fluorescence (EDXRF) spectrometric method for the determination of low concentrations of sulfur in automotive fuels. The method targets sulfur levels in the range 8 mg/kg to 50 mg/kg for motor gasolines (including blends with up to 10% v/v ethanol and up to 3.7% m/m oxygen) and diesel fuels (including up to ~10% v/v FAME). The procedure covers instrument performance, sample handling, calibration and quality control to support reliable low‑sulfur measurements by EDXRF.

Key topics and technical requirements

• Analytical principle: measurement of sulfur K–L characteristic X‑radiation from a liquid fuel test portion in an X‑ray transparent sample cup; comparison with calibration standards.
• Scope limits: not applicable to leaded gasoline or products containing lead, silicon, phosphorus, calcium, potassium or halides at concentrations > 0.1 × [S] or > 10 mg/kg (whichever is greater).
• Measurement range: validated for 8–50 mg/kg sulfur in automotive fuels.
• Instrument performance:
  • Adequate signal‑to‑background for a 10 mg/kg standard and coefficient of variation (based on repeated measurements) < 5%.
  • X‑ray source with significant flux above 2.5 keV; detector resolution ≤ 800 eV at 2.3 keV.
  • Sample cup depth ≥ 5 mm and replaceable X‑ray film (polyester preferred, 2–6 µm).
• Calibration and standards:
  • Use CRMs or primary standards prepared from specified sulfur compounds (e.g., dibenzothiophene, dibutylsulfide, benzothiophene, dibutyldisulfide).
  • Prepare primary standards (~500 mg/kg and 1 000 mg/kg) and multi‑point calibration covering the target range.
• Sample handling & preparation:
  • Sampling per ISO 3170 / ISO 3171; refrigerate light fractions; mix by gentle shaking; allow test portions to reach ambient temperature.
  • Use disposable cups or rigorously cleaned reusable cups and consistent window film batches.
• Quality control: use CRMs and stable QC samples; follow recommended instrument warm‑up and optional helium purge for stability.
• Matrix effects: guidance included for matrix matching or instrument‑based matrix correction to improve accuracy.

Applications and users

• Fuel quality and compliance testing laboratories verifying low‑sulfur gasoline and diesel for regulatory and commercial specifications.
• Refinery and fuel blending QA/QC teams monitoring sulfur in finished fuels and blends (including ethanol or FAME blends).
• Environmental and emissions testing labs where accurate low‑level sulfur data are required for regulatory reporting.
• Instrument manufacturers and metrology labs validating EDXRF systems for petroleum analysis.

Related standards

• ISO 3170 (manual sampling of petroleum liquids)
• ISO 3171 (automatic pipeline sampling)
• ISO 20847 (related sulfur analysis methods)
  (Note: ISO 13032:2012 is also based on the Energy Institute IP test method PM DU.)

Keywords: ISO 13032:2012, EDXRF, sulfur determination, low sulfur fuels, automotive gasoline, diesel, calibration, CRMs, fuel quality testing.