Overview
ISO/TS 23647:2010 specifies a validated gas chromatography (GC) method for the determination of wax content in vegetable fats and oils. The method applies to crude, degummed, neutralized, winterized and fully refined oils (for example sunflower, soybean, rapeseed, corn and rice bran oils) but is not applicable to olive oils or olive‑pomace oils. Waxes-defined as esters of long‑chain fatty acids and fatty alcohols with saturated chains of C20 or longer-are quantified and reported as milligrams per kilogram (mg/kg) of oil.
Key topics and technical requirements
- Sample preparation: laboratory sample heating (up to 130 °C) and preparation per ISO 661 to melt crystallized waxes and remove moisture.
- Separation principle: column chromatography using a mixed packing of silica gel and AgNO3‑impregnated silica gel (5 % AgNO3) to isolate waxes from triacylglycerols and other non‑glyceridic components.
- Solvent systems and flow rates:
- Solvent A: n‑hexane (95 %) / dichloromethane (5 %) for sample loading and washing.
- Solvent B: n‑hexane (80 %) / dichloromethane (20 %) for elution (190 ml recommended).
- Typical column flow rates: 1.5–2.0 ml/min for loading and ~3 ml/min for elution.
- Concentration and cleanup: evaporative concentration of eluate and re‑dissolution in chloroform prior to GC.
- GC determination:
- Recommended column: fused silica capillary (25 m × 0.20 mm, 0.11 µm dimethylpolysiloxane).
- Oven program: 170 °C (0.1 min), ramp to 350 °C at 6 °C/min, hold 20 min.
- Carrier gas: H2; injector ~355 °C (split 1:30); FID ~360 °C.
- Internal standard: hexatriacontane and use of stearyl stearate for response factor determination.
- Quality features: precision data from interlaboratory tests, test reporting requirements and chromatogram examples (Annexes A–C).
Applications and practical value
- Quality control in edible oil refining: measure residual wax after dewaxing/winterization to assess process efficiency and product clarity.
- Industrial process monitoring: optimize dewaxing operations for sunflower, rice bran, corn and seed oils.
- Analytical laboratories and contract testing: standardized GC protocol for consistent wax quantification (mg/kg).
- Research and product development: characterize minor components and wax composition in vegetable oils.
- Helps predict and prevent cold‑temperature cloudiness or crystallization in finished oils and oils intended for cold climates.
Who should use this standard
- Oil refiners and processors
- QC and analytical laboratories
- Food safety and regulatory bodies
- Suppliers and traders requiring specification compliance
- Academic and industrial researchers in lipid analysis
Related standards
- ISO 661 - Preparation of test sample (referenced for sample prep)
- ISO 5555 - Recommended sampling of edible fats and oils (sampling guidance)
Keywords: ISO/TS 23647:2010, wax content, gas chromatography, vegetable oils, wax determination, dewaxing, GC method, sunflower oil, hexatriacontane, AgNO3 silica gel.