Overview
ISO 8892:1987 specifies a laboratory method for the determination of total residual hexane (expressed as n‑hexane) in oilseed residues after solvent extraction. The method uses thermal desorption with water in a sealed vial and headspace gas chromatography (HS‑GC) with a flame ionization detector (FID) to quantify volatile hydrocarbons commonly present in technical hexane solvents.
Keywords: ISO 8892:1987, oilseed residues, residual hexane, headspace GC, solvent residues, n‑hexane.
Key topics and technical requirements
- Scope: Measurement of volatile hydrocarbons (referred to as hexane) remaining in oilseed residues after hydrocarbon extraction.
- Sampling & storage: Follow ISO 5500; laboratory sample must be sealed (metal container preferred) and stored at −20 °C or below. Plastics containers are not recommended.
- Test portion & preparation: Typical test portion is 5.0 g of sample hydrated with 2.5 ml distilled water in a 50–60 ml crimped vial; seal with a solvent‑resistant septum and foil cap.
- Desorption conditions: Place vials in an oven at 110 °C for 90 minutes, then cool 2 minutes and agitate before headspace sampling.
- Headspace sampling: Withdraw 0.5 ml headspace gas with a heated (50–60 °C) gas syringe and inject immediately into the GC.
- Gas chromatography parameters: FID detector; recommended capillary column ~30 m × 0.3 mm, coated with methylpolysiloxanes (or packed column ≥1.7 m on acid‑washed diatomaceous earth). Typical injector/detector 120 °C, oven ~40 °C, carrier gas pressure ~0.3 bar.
- Calibration & quantification: Use a calibration series (e.g., three points such as 2, 5, 10 µl of n‑hexane in the vial) and plot peak area versus mass. Results reported as mg hexane/kg residue, mean of two determinations.
- Precision: International interlaboratory tests reported mean residual hexane values and repeatability/reproducibility. Reproducibility coefficients of variation in examples ranged roughly 21–32% depending on residue type.
Applications and users
- Laboratories performing solvent‑residue analysis and method validation.
- Oilseed processors and refiners for quality control and verification of solvent removal.
- Food safety and regulatory bodies monitoring residual solvent levels in oilseed meal and by‑products.
- R&D teams developing extraction or solvent‑recovery processes.
Practical uses include compliance testing, process optimization (ensuring adequate solvent removal), and routine QC of oilseed residues destined for animal feed or further processing.
Related standards
- ISO 5500 - Oilseed residues: Sampling (referenced within ISO 8892 for sample collection and handling).
This summary highlights the practical workflow and technical requirements of ISO 8892:1987 for measuring residual hexane in oilseed residues using headspace GC.
