Overview
ISO 12977:1999 specifies an empirical gas chromatographic method to determine the volatile matter content of electrode pitch used in aluminium production. The standard defines volatile matter as the total percentage by mass of pitch components whose gas‑chromatographic retention times correspond to atmospheric‑pressure boiling points up to 360 °C under the prescribed conditions. Because the procedure is empirical, strict adherence to the method, reagents and chromatographic conditions is essential.
Key topics and technical requirements
- Analytical principle: Simulated distillation by GC - establish a linear relationship between chromatographic retention time and atmospheric boiling point for a set of calibrant compounds, then calculate the mass fraction boiling ≤ 360 °C.
- Reagents and calibrants:
- Internal standard: dibenzothiophene (≥98% purity). Analysis is performed with and without added dibenzothiophene because it may be present in the pitch.
- Calibrant mixture: naphthalene, 2‑methylnaphthalene, acenaphthene, dibenzofuran, fluorene, phenanthrene, fluoranthene and pyrene (all ≈ ≥98% purity).
- Solvent: toluene (analytical quality).
- Apparatus and chromatographic setup:
- Gas chromatograph with heated injector (capable of ~300 °C), flame‑ionization detector (FID) and programmed temperature control (≈50–300 °C).
- Non‑polar, low‑bleed capillary column (poly(dimethylsiloxane) type recommended).
- Electronic integrator to record retention times and peak areas.
- Sample preparation:
- Representative sampling per ISO 6257.
- Grind and sieve to pass a 212 µm test sieve.
- Prepare two test solutions (with and without internal standard) in toluene, using ultrasonic treatment and settling/filtration to minimise insolubles.
- Calibration & calculation: Determine response factors from the calibrant solution, construct the retention time vs boiling point relationship and compute the simulated distillation to obtain the volatile matter percentage.
- Quality aspects: The standard includes precision, calculation, reporting requirements and an informative annex with boiling points of calibrants.
Applications and users
- Who uses it:
- Analytical laboratories supporting the aluminium industry
- Quality control teams at electrode pitch and carbonaceous material manufacturers
- Process engineers monitoring feedstock properties in aluminium smelting
- Practical uses:
- Quality assessment of pitch for electrodes
- Process control and material specifications verification
- Raw material acceptance testing and supplier qualification
Related standards
Keywords: ISO 12977, volatile matter, pitch for electrodes, carbonaceous materials, gas chromatography, dibenzothiophene, aluminium production, simulated distillation.