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International Organization for Standardization

ISO 20483

Cereals and pulses — Determination of nitrogen content and calculation of crude protein content — Kjeldahl method.

What it measures

Nitrogen content of cereals, pulses and derived products, with calculation of crude protein content, by the Kjeldahl method.

Application

Grain, cereal and pulse laboratories — the routine reference for protein in wheat, rice, legumes and milled products.

Method principle.

Kjeldahl: catalytic digestion in concentrated sulphuric acid, alkaline steam distillation into boric acid, then titration of the absorbed ammonia. Read the full Kjeldahl method note →

Laboratory workflow.

Step 1

Digestion

The sample is digested in concentrated sulphuric acid with a catalyst on a digestion block (Smart, X, S or Gr series), converting organic nitrogen to ammonium.

Step 2

Distillation

Alkali is added and steam distillation releases the ammonia, which is absorbed in boric acid — automated on every K-series analyzer.

Step 3

Titration

The absorbed ammonia is titrated to a colorimetric end point detected by a 16-bit tri-primary color sensor (built in on K06, K12, K18 and K1306; external on K1305/K1301).

Step 4

Data handling

Results are calculated, stored and exported — K12/K18 store up to 5,000,000 test results with USB, Wi-Fi and host-control output; K18 adds LIMS connectivity.

Relevant SONNEN instruments.

K1305K1305 Automated Kjeldahl Nitrogen Analyzer, Kjeldahl Distillation Unit→ K1301K1301 Semi-Automated Kjeldahl Nitrogen Analyzer, Kjeldahl Distillation Unit→ K12K12 Fully Automated Kjeldahl Nitrogen Analyzer, Kjeldahl Distillation and Titration System→ K18K18 Fully Automated Kjeldahl Nitrogen Analyzer, Kjeldahl Distillation and Titration System→ K1306K1306 Fully Automated Kjeldahl Nitrogen Analyzer, Kjeldahl Distillation and Titration System→ Gr20Gr20 Automated Graphite-Block digester→

FAQ.

Which SONNEN analyzers list ISO 20483?
The K1305 and K1301 Kjeldahl distillation units list ISO 20483 among their applicable standards; the fully automated K12, K18 and K1306 systems run the same digestion–distillation–titration procedure with built-in titration.
How fast is a cereal protein determination on the K series?
The K-series specification lists 3–8 minutes per sample for the distillation/titration step, over a 0.1–240 mg N measuring range.
Related standards & methods
Kjeldahl method ISO 1871 ISO 8968 (IDF 20) series AOAC 981.10 GB/T 22923-2008 JJF 109-2012

Working to ISO 20483?

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