Overview
EN ISO 8892:1995 (ISO 8892:1987) specifies a laboratory method for the determination of total residual hexane in oilseed residues after solvent extraction. The procedure quantifies volatile hydrocarbon residues (commonly referred to as hexane) by thermally desorbing the solvent into a closed vessel and analysing the headspace by gas chromatography (GC) with flame ionization detection (FID). Results are expressed as milligrams of n‑hexane per kilogram of residue.
Key topics and technical requirements
- Scope and purpose: Measurement of volatile hydrocarbon residues remaining in oilseed meals and residues after hydrocarbon-based extraction.
- Sampling and storage: Follow ISO 5500 for sampling. Laboratory samples must be hermetically sealed (metal preferred), stored at −20 °C or below, and analysed promptly to avoid hexane loss.
- Sample preparation: Typical test portion is 5 g of residue mixed with 2.5 ml distilled water in a 50–60 ml septum-sealed flask.
- Desorption conditions: Heat sealed flasks at 110 °C (oven) to desorb hexane into the headspace (90 min for test samples; calibration flasks treated for 15 min as specified).
- Headspace sampling and GC analysis:
- Headspace sample: 0.5 ml withdrawn at 50–60 °C with a heated gas syringe.
- Detector: Flame ionization detector (FID).
- Columns: Capillary column (~30 m × 0.3 mm, methylpolysiloxane) or packed column (≥1.7 m) coated with methylpolysiloxane.
- Injector/detector temperatures and carrier gas conditions are specified for reproducible peak response.
- Calibration and expression of results: Use calibration flasks prepared with known hexane masses; express results as n‑hexane and report the arithmetic mean of two determinations.
- Precision data: Interlaboratory studies (multiple labs) provide repeatability and reproducibility statistics; reproducibility variability can be significant for some residues and should be considered in interpretation.
Practical applications and users
- Laboratories performing residual solvent testing for oilseed meals (soy, sunflower, rape/colza).
- Quality control teams in oilseed extraction and vegetable oil processing plants for process monitoring and release testing.
- Food and feed safety laboratories ensuring compliance with regulatory or purchaser limits for solvent residues.
- Method developers and accreditation bodies validating headspace‑GC procedures for residual hydrocarbons.
Related standards
- ISO 5500 - Oilseed residues: sampling (referenced for sample handling).
- ISO 5725 - Precision of measurement methods (used for interlaboratory statistics).
Keywords: EN ISO 8892:1995, ISO 8892, oilseed residues, residual hexane, hexane determination, gas chromatography, headspace analysis, solvent residue testing.