ASTM E258 Total Nitrogen Testing in Organic Materials by Modified Kjeldahl
The ASTM E258-07 test method determines the total nitrogen content of certain unknown organic compounds. The ASTM E258-07 test method performs on organic materials in which the complete conversion of nitrogen to ammonium sulfate takes place. Kjeldahl digestion flask apparatus is used in this test method.
TRUSTED BY
- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
ASTM E258 Total Nitrogen in Organic Materials Overview
ASTM E258 describes the standard test method for determining total nitrogen in organic materials using the modified Kjeldahl method. The sample is digested with sulfuric acid and a catalyst to convert all organic nitrogen to ammonium sulfate, which is then distilled and titrated to quantify total nitrogen content.
Nitrogen determination is a fundamental analytical measurement for characterizing proteins, amino acids, fertilizers, pharmaceuticals, polymers containing nitrogen-based functional groups, and organic nitrogen compounds used in industrial synthesis.
Scope, Applications, and Benefits
Scope
ASTM E258 evaluates:
- Total Kjeldahl nitrogen (TKN) in organic materials
- Applicable to solid and liquid organic samples
- Covers primary, secondary, and tertiary amines and amides
- Results expressed as wt% N or protein equivalent (N × 6.25)
Applications
- Protein content determination in food, feed, and agricultural materials
- Pharmaceutical active ingredient nitrogen content verification
- Fertilizer nitrogen grade certification
- Nitrogen-containing polymer and resin characterization
- Industrial organic nitrogen compound purity analysis
Benefits
- Well-established, highly reliable nitrogen determination method
- Applicable to virtually all organic nitrogen-containing matrices
- Provides traceable, internationally recognized results
- Supports protein calculation for nutritional labeling
- Complies with AOAC, USP, and ISO fertilizer analysis standards
ASTM E258 Total Nitrogen in Organic Materials Test Process
Acid Digestion
Digest sample with H₂SO₄, convert nitrogen to ammonium sulfate
1Alkalization & Distillation
Add NaOH, distill ammonia into boric acid or HCl
2Titration
Titrate ammonia with HCl or back-titrate using NaOH
3Nitrogen Calculation
Calculate nitrogen wt% from titration data and sample mass
4ASTM E258 Total Nitrogen in Organic Materials Technical Specifications
| Parameter | Details |
|---|---|
| Applicable Materials | Organic compounds, food, feed, fertilizers, pharmaceuticals |
| Sample Mass | 0.1–2 g (concentration dependent) |
| Nitrogen Range | 0.05–50 wt% N |
| Catalyst | Se, Cu, or K₂SO₄/CuSO₄ mixture |
Instrumentation Used for Testing
- Kjeldahl digestion block and fume scrubber
- Steam distillation unit (Kjeldahl distillation apparatus)
- Analytical balance (±0.1 mg)
- Potentiometric autotitrator
- Standardized HCl and NaOH titrants
- Certified nitrogen reference materials (EDTA, tryptophan)
Results and Deliverables
- Total nitrogen content (wt% N)
- Protein equivalent (wt%, using appropriate conversion factor)
- Blank-corrected titration data
- Recovery verification with reference material
- Full ASTM E258 nitrogen analysis report
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Frequently Asked Questions
ASTM E258-07 is a standard test method used to determine total nitrogen in organic materials using the modified Kjeldahl method for accurate chemical analysis.
ASTM E258-07 is important because nitrogen content affects composition, quality, and performance, making it essential for analysis in agriculture, chemicals, and environmental applications.
ASTM E258-07 involves digestion of the sample to convert nitrogen into ammonium, followed by distillation and titration to quantify total nitrogen.
ASTM E258-07 requires digestion units, distillation apparatus, titration setup, and analytical reagents for accurate nitrogen determination.
ASTM E258-07 results are reported as total nitrogen content, typically in percentage, indicating composition and suitability for intended applications.
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