ISO 8968 (IDF 20) series
Milk and milk products — Determination of nitrogen content (parts 2, 3 and 4).
Nitrogen content of liquid milk, whole or skimmed — total nitrogen (part 2, block-digestion principle; part 3, semi-micro method) and non-protein nitrogen (part 4).
Dairy laboratories determining protein, non-protein nitrogen and casein-related fractions in milk and milk products.
Method principle.
Kjeldahl block digestion followed by steam distillation and titration; the ISO 8968 parts correspond to the IDF/FIL 20 series (20-2, 20-3, 20-4). Read the full Kjeldahl method note →
Laboratory workflow.
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.
Distillation
Alkali is added and steam distillation releases the ammonia, which is absorbed in boric acid — automated on every K-series analyzer.
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).
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.
FAQ.
Which parts of ISO 8968 do Sonnen instruments list?
What dairy samples fit the workflow?
Working to ISO 8968 (IDF 20) series?
Tell us your sample type — we will map the instrument to the method.