ISO 7836:2024

Overview

ISO 7836:2024 - Natural rubber - Identification of phytosterols, including β-sitosterol specifies a laboratory method to detect the presence (presence/absence) of phytosterols, notably β‑sitosterol, in natural rubber in raw, vulcanised and latex forms. The standard uses acetone extraction followed by thin layer chromatography (TLC) with comparison to a β‑sitosterol standard. Results confirm whether natural rubber (which uniquely contains β‑sitosterol among cis‑1,4‑polyisoprene rubbers) is present.

Key topics and technical requirements

• Scope: Identification (qualitative) of phytosterols including β‑sitosterol in natural rubber (raw, vulcanised, latex).
• Extraction: Acetone extraction per procedure; 2–5 g sample; rotary evaporation (≤60 °C) and oven drying prior to re‑dissolution in acetone.
• TLC method:
  • Silica gel plates activated (105 °C for 2 h or 80 °C overnight).
  • Developing solvent: petroleum ether : diethyl ether (60:40 by volume).
  • Spotting: 2–5 µl of sample and standard β‑sitosterol (>95 %).
  • Spray reagent: cupric acetate + phosphoric acid solution; β‑sitosterol appears purple after spraying and drying.
  • Identification: compare Rf of sample spot to standard; match within ±5 % confirms presence.
• Detection limit: minimum detection of natural rubber is approximately 3 %.
• Expression of results: reported as presence or absence of β‑sitosterol.
• Reporting requirements: include reference to ISO 7836:2024, sample identification, test result, detection limit, any deviations or unusual features, and test date.

Practical applications and users

• Quality control and raw‑material verification in the rubber industry - distinguishing natural rubber from synthetic cis‑1,4‑polyisoprene.
• Incoming goods inspection and supplier verification for tyre, automotive, pharmaceutical rubber goods and specialty elastomer manufacturers.
• Materials testing laboratories and forensic/materials analysts validating the botanical origin of rubber.
• Research and development groups performing composition analysis or product authentication.

Benefits:

• Simple, cost‑effective qualitative test using standard TLC equipment.
• Useful as a complementary method alongside polymer characterization techniques (e.g., FTIR, protein tests) to confirm natural rubber content.

Related standards

• ISO 124 - Latex, rubber - Determination of total solids content (referenced for latex sample prep).
• ISO 1407 - Rubber - Determination of solvent extract (referenced for extraction procedure).

Note: Users should follow normal laboratory safety practices. ISO provides the full procedural details and normative references in ISO 7836:2024.