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.
Run this determination on an automatic Kjeldahl analyzer — the K12 completes distillation and titration unattended, and pairs with an autosampler for 20/35-sample batches.
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.