Overview
ISO 23956:2022 - Traditional Chinese medicine: Determination of benzopyrene in processed natural products - specifies validated laboratory methods to detect and quantify benzopyrene (benzo[a]pyrene, BaP) in heat‑processed herbal materials used in Traditional Chinese Medicine (TCM). The standard covers processed plant products such as processed Rehmannia root, processed Cyperus rhizome, processed ginseng and processed mume fruit (not applicable to mineral TCMs). It responds to carcinogenicity concerns (IARC Group 1) about BaP formation during high‑temperature processing (200–600 °C).
Key topics and technical requirements
- Scope and definitions: Benzopyrene (C20H12) and related polycyclic aromatic hydrocarbons (PAHs).
- Sample preparation: Typical procedure - 5 g sample powder extracted in water, hexane extraction with an internal standard (3‑methylcholanthrene), drying over anhydrous sodium sulfate, rotary evaporation, Florisil SPE cleanup, nitrogen concentration and filtration prior to analysis.
- Internal standard & calibration:
- Internal standard: 3‑methylcholanthrene (analysis grade).
- Stock solutions: BaP and internal standard at 1 μg/ml (store at 4 °C; replace every six months).
- Calibration points: 3, 5, 10, 20 and 40 ng/ml with 50 ng/ml internal standard.
- HPLC‑FLD method:
- Column: Supelcosil LC‑PAH 4.6 × 250 mm, 5 μm (or equivalent).
- Mobile phase: acetonitrile:water (8:2), flow 1.0 ml/min, column temp 35 °C.
- FLD detection: excitation 294 nm, emission 404 nm.
- Identification by retention time within ±0.2% of standard.
- GC‑MS method:
- Column: 5% phenylmethylsiloxane, 30 m × 0.25 mm × 0.25 μm.
- Carrier gas He 1 ml/min; injection 300 °C; transfer line 280 °C; stepped oven program to 310 °C.
- Detection by electron impact ionization (70 eV) in selected ion monitoring (SIM) mode (BaP quantifier ion m/z 252; qualifiers m/z 253, 125).
- Quality control: SPE cleanup, use of internal standard, linear calibration curve and defined chromatographic/ion criteria.
Applications
- Routine quality control testing of processed herbal TCM products for BaP contamination.
- Regulatory compliance testing to meet national limits (e.g., Germany smoked BaP 1 ng/g; China total PAHs 5 ng/g; Republic of Korea processed Rehmannia BaP 5 ng/g).
- Risk assessment and product safety verification after thermal processing or traditional roasting/smoking steps.
- Method transfer, validation and proficiency testing in testing laboratories.
Who should use this standard
- TCM manufacturers and processors applying heat treatments.
- Analytical laboratories (pharmacopoeial, contract testing, QC labs) performing HPLC‑FLD or GC‑MS analyses.
- Regulatory bodies and inspectors developing or enforcing limits on PAHs in herbal medicines.
- Research groups studying formation and mitigation of PAHs in processed natural products.
Related standards and references
- Prepared by ISO/TC 249 (Traditional Chinese medicine).
- The document references national pharmacopeia methods, national regulations and other standardized PAH test methods (see Annex B for country limits and Annexes A–D for chemical data, example chromatograms and alternate cases).
Keywords: ISO 23956, benzopyrene, benzo[a]pyrene, BaP, PAH, HPLC‑FLD, GC‑MS, Traditional Chinese Medicine, processed natural products, quality control, analytical method.