Overview
ISO 6870:2002 specifies a qualitative screening method for the detection of zearalenone in animal feeding stuffs, with particular emphasis on maize. The method is intended for screening (not quantitative compliance testing) and has a reported limit of determination of approximately 50 µg/kg. The procedure uses two-dimensional thin‑layer chromatography (2D‑TLC) with UV fluorescence detection and a confirmatory spray (bis‑diazotized benzidine).
Key topics and technical requirements
- Scope: Qualitative screening of zearalenone in animal feedstuffs (maize emphasized). Sorghum interference is addressed by 2D chromatographic separation and the specified confirmation technique.
- Sample preparation: Grind to 1 mm, 50 g test portion, extract with acetonitrile and KCl solution, defat with isooctane, concentrate.
- Purification: Treat extract with lead acetate in the presence of diatomaceous earth (Celite), then extract into chloroform and evaporate.
- Chromatography: Dissolve residue in benzene/acetonitrile and perform two‑direction TLC using specified solvent systems; apply standard spots alongside sample for comparison.
- Detection & confirmation:
- Visual comparison of UV‑induced fluorescence (short‑wave UV) or measurement by fluorodensitometer (preferred where available).
- Confirm identity by spraying with bis‑diazotized benzidine reagent (zearalenone produces a brick‑red spot).
- Performance & precision: An interlaboratory study (Annex A) summarizes repeatability and reproducibility data for maize matrices; the method is explicitly for screening and precision values are matrix/concentration dependent.
- Safety: The method uses hazardous solvents and reagents (chloroform, benzene, benzidine). Use fume hoods, appropriate PPE, and follow laboratory safety rules.
Practical applications
- Rapid screening of feed materials (especially maize) for zearalenone contamination before more definitive testing.
- On‑site or laboratory feed safety monitoring programs to flag suspect batches for follow‑up quantitative analysis.
- Pre‑screening in feed manufacturing, grain trading, quality control, and regulatory surveillance to prioritize samples for confirmatory methods (e.g., LC‑MS/MS).
- Useful where a cost‑effective, relatively simple TLC‑based screening is required.
Who should use this standard
- Feed testing laboratories and QC departments in feed mills.
- Regulatory authorities and inspection labs conducting feed surveillance.
- Grain traders and storage facilities implementing rapid screening protocols.
- Analysts familiar with thin‑layer chromatography and laboratory safety procedures.
Related standards
- Prepared by ISO/TC 34 / SC 10 (Animal feeding stuffs).
- Precision evaluation in the standard references ISO 5725 methodology for repeatability and reproducibility.
Keywords: ISO 6870:2002, zearalenone, animal feeding stuffs, maize, qualitative screening, thin‑layer chromatography, 2D‑TLC, bis‑diazotized benzidine, feed safety.
