GB/T 22923-2008 — China national standard — determination of nitrogen, phosphorus and potassium in chemical fertilizers by automatic analyzer

What it measures

Nitrogen, phosphorus and potassium in chemical fertilizers by automatic analysis apparatus — the field in which Sonnen's Kjeldahl line was first standardized.

Application

Fertilizer inspection stations and fertilizer manufacturers determining nitrogen content for product compliance.

Method principle.

Automated Kjeldahl determination: digestion, alkaline steam distillation and colorimetric end-point titration on an automatic nitrogen analyzer. Read the full Kjeldahl method note →

SONNEN’s role: Sonnen was invited to participate in drafting GB/T 22923-2008 (Determination Method of Chemical Fertilizer) in 2008, after winning the determination-comparison test organized by the China National Fertilizer Testing Center with three rounds of comparative results.

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.

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→ Smart 20Smart 20 Automated Aluminum-Block digester→

FAQ.

What is SONNEN's role in GB/T 22923-2008?

Sonnen is one of the co-drafters of the standard. The company was invited to participate in 2008 after its analyzer matched the imported reference instrument point for point in a three-round comparison organized by the China National Fertilizer Testing Center.

Which instruments are built for fertilizer nitrogen?

The K12, K18 and K1306 distillation–titration systems list GB/T 22923-2008 among their applicable standards, with a dedicated high-nitrogen test mode for samples above 45% nitrogen content.

Related standards & methods

Kjeldahl method ISO 1871 ISO 20483 ISO 8968 (IDF 20) series AOAC 981.10 JJF 109-2012

Working to GB/T 22923-2008?

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