ISO 5983-2-2009 PDF

Full title and description

St ISO 5983-2-2009 — Animal feeding stuffs — Determination of nitrogen content and calculation of crude protein content — Part 2: Block digestion and steam distillation method. This part of ISO 5983 specifies a semi‑micro Kjeldahl procedure using block digestion (copper catalyst) and steam distillation into boric acid for routine determination of Kjeldahl nitrogen and calculation of crude protein in animal feeds, pet foods and related raw materials.

Abstract

ISO 5983-2:2009 defines a rapid, semi‑micro Kjeldahl method suitable for samples containing greater than 0.5 % (mass fraction) Kjeldahl nitrogen. The procedure uses concentrated sulfuric acid digestion with potassium sulfate and a copper catalyst, followed by alkali liberation of ammonia, steam distillation into boric acid and titrimetric determination. The method does not measure oxidized forms of nitrogen or heterocyclic nitrogen compounds and does not distinguish protein nitrogen from non‑protein nitrogen.

General information

• Status: Published (International Standard).
• Publication date: 2009 (Edition 2 — published June 2009 / 26 May 2009 in some catalogues).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 65.120 (Food products — Animal feeding stuffs).
• Edition / version: Edition 2 (2009).
• Number of pages: 15 (ISO bibliographic record; some national/adopted versions list minor differences in page count).

Scope

This part of ISO 5983 applies to the determination of Kjeldahl nitrogen (and calculation of crude protein by a factor of 6.25 unless otherwise specified) in animal feeding stuffs, pet foods and their raw materials where Kjeldahl nitrogen is greater than approximately 0.5 % (mass fraction). It is intended as a semi‑micro, rapid routine method using block digestion, copper catalyst and steam distillation into boric acid. The method excludes measurement of oxidized nitrogen species and heterocyclic nitrogen compounds and does not separate protein and non‑protein nitrogen.

Key topics and requirements

• Principle: Acid digestion (concentrated H2SO4 with K2SO4 to raise boiling point and a copper catalyst) converts organic nitrogen to ammonium sulfate; addition of alkali liberates NH3, which is steam‑distilled into boric acid and quantified by titration (visual indicator or potentiometric endpoint).
• Reagents: high‑purity concentrated sulfuric acid, Kjeldahl catalyst (e.g., copper sulfate with potassium sulfate), hydrogen peroxide (where required), sodium hydroxide for alkalisation, boric acid trapping solution, standard acid titrant for quantification.
• Apparatus: block digestion unit (temperature control ≈420 °C), digestion tubes, steam distillation apparatus (manual, semi‑automatic or automatic), analytical balance with 0.1 mg readability, burette or automatic titrator and pH/endpoint detection.
• Sample sizes and mass ranges: guidance given for typical sample masses depending on expected nitrogen/protein content (to avoid overloading digestion and ensure accurate titration).
• Quality control and performance: method includes recommendations for blanks, use of reference or control materials (e.g., acetanilide, tryptophan, ammonium sulfate), and reports precision data (repeatability / reproducibility) and safety precautions for handling hazardous reagents.
• Limitations: not suitable for determination of oxidized nitrogen species (e.g., nitrate/nitrite) or for distinguishing protein vs non‑protein nitrogen without additional procedures.

Typical use and users

Widely used by feed testing laboratories, quality control departments in the animal feed and pet food industry, research institutions studying feed composition, and regulatory or certification bodies that require standardized crude protein reporting. The method is designed for routine, high‑throughput analysis where a robust Kjeldahl result for crude protein is required.

Related standards

ISO 5983 is a multi‑part series. Part 1 (ISO 5983‑1:2005) covers the Kjeldahl method more generally and remains a related reference; ISO 5983‑2:2009 revised and replaced ISO 5983‑2:2005 (the 2005 edition was withdrawn when the 2009 edition was published). Other related references include ISO 1871 (food — guidelines for Kjeldahl nitrogen determination) and sample preparation guidance such as ISO 6498. National or regional adoptions (EN/ISO versions) may also exist.

Keywords

Kjeldahl, nitrogen, crude protein, animal feeding stuffs, pet food, block digestion, steam distillation, boric acid, copper catalyst, routine analysis.

FAQ

Q: What is this standard?

A: ISO 5983-2:2009 is the second part of the ISO 5983 series that specifies a block‑digestion + steam‑distillation Kjeldahl method for determining Kjeldahl nitrogen and calculating crude protein in animal feeding stuffs and related materials.

Q: What does it cover?

A: It covers the analytical principle, required reagents and apparatus, recommended sample sizes, procedural steps for digestion, distillation and titration (visual or potentiometric endpoint), quality control measures and limitations of the method (e.g., it does not measure oxidized nitrogen or distinguish protein vs non‑protein nitrogen).

Q: Who typically uses it?

A: Accredited testing laboratories, industrial QC labs in the feed and pet food sectors, academic and research laboratories working on feed composition, and regulatory/certification bodies that require standardized protein reporting in feed materials.

Q: Is it current or superseded?

A: ISO 5983-2:2009 is the current ISO edition for Part 2 (published 2009). ISO bibliographic records show the 2009 edition as published and the earlier 2005 edition withdrawn on revision; the ISO record also documents periodic systematic reviews and confirmations (for example, confirmation actions were recorded in 2019). Users who need the absolute latest status (beyond the bibliographic review history) should check ISO’s official catalogue or their national standards body for any amendments or newer editions.

Q: Is it part of a series?

A: Yes — ISO 5983 is a multipart series concerned with nitrogen and crude protein determination in animal feeding stuffs. Part 1 (ISO 5983‑1:2005) addresses the Kjeldahl method in general; Part 2 (this document) addresses the block digestion/steam distillation variant. Other normative references (ISO 1871, ISO 6498, etc.) provide complementary guidance.

Q: What are the key keywords?

A: Kjeldahl, nitrogen, crude protein, animal feed, block digestion, steam distillation, boric acid, copper catalyst, routine analysis, feed testing.