Overview
EN ISO 16634-1:2008 (CEN endorsed) specifies a laboratory method for the determination of total nitrogen by combustion according to the Dumas principle and the subsequent calculation of crude protein in oilseeds and animal feeding stuffs. The standard defines the analytical principle, required reagents and apparatus, sampling and test-sample preparation, calibration and calculation procedures. It notes that, like the Kjeldahl method, the Dumas method does not distinguish protein nitrogen from non‑protein nitrogen and is not applicable to milk and milk products.
Keywords: EN ISO 16634-1:2008, Dumas method, total nitrogen, crude protein, oilseeds, animal feeding stuffs, protein content determination.
Key topics and requirements
- Principle: Combustion of sample to convert nitrogenous compounds to gases; interfering components removed; nitrogen determined (typically by thermal conductivity detection).
- Reagents & gases: High-purity carrier gas (helium or CO2) and oxygen; catalysts and absorbents (e.g., CuO, platinum catalyst, drying agents) are specified to ensure complete combustion and gas cleanup.
- Apparatus & calibration: Guidance on Dumas apparatus design, post‑combustion materials, reduction tubes and calibration procedures (including instrument calibration annexes).
- Sampling & sample prep: Cross-references to ISO standards for sample reduction and moisture determination to ensure representative test portions.
- Calculation: Conversion of measured nitrogen to crude protein using standard conversion factors (Annex D). The standard highlights the need to select appropriate factors because Dumas and Kjeldahl results can differ slightly.
- Quality & precision: Contains sections and annexes on precision, repeatability, reproducibility and results from collaborative studies to support method validation.
Practical applications and users
EN ISO 16634-1:2008 is intended for laboratories and organizations involved with:
- Oilseed processors and traders assessing protein in seeds (e.g., soy, rape, sunflower).
- Animal feed manufacturers and quality control teams monitoring feed protein specifications.
- Food analysis laboratories adopting faster, non‑hazardous alternatives to Kjeldahl for nitrogen/protein testing.
- Regulatory bodies and inspection labs requiring standardized, comparable protein data.
- Instrument manufacturers developing or validating Dumas combustion analyzers.
Benefits include faster throughput and avoidance of hazardous chemicals compared with Kjeldahl, while providing internationally recognized procedures for consistent protein reporting.
Related standards
- ISO 14891 / IDF 185 - methods for milk and milk products (Dumas not applicable here).
- ISO 16634 series - Part 2 (in preparation) covers cereals, pulses and milled cereal products.
- Normative references cited: ISO 664, ISO 665, ISO 771, ISO 6496, ISO 6498 (sampling, moisture and sample preparation standards).
Use EN ISO 16634-1:2008 when you need a standardized, validated Dumas combustion method for reliable total nitrogen and crude protein determination in oilseeds and animal feeding stuffs.