Overview - ISO 15672:2000 (total nitrogen in rubber)
ISO 15672:2000 specifies an instrumental method for the determination of total nitrogen in rubber and rubber additives using an automatic analyser. The standard defines the principle, apparatus function, calibration and procedural controls for converting nitrogen-containing materials into measurable gaseous products and quantifying nitrogen concentration. It is intended for laboratories familiar with normal laboratory practice and relevant safety procedures.
Key topics and technical requirements
- Scope: Instrumental (automatic analyser) method for total nitrogen in rubber and additives.
- Principle: Convert nitrogen-containing material to nitrogen oxides by combustion in oxygen, reduce oxides to elemental nitrogen (copper at elevated temperature) and detect nitrogen using one of three configurations:
- Thermal conductivity detection (sequential removal of H2O and CO2, then TCD for N2)
- Combined absorbance/conductivity detection (IR for CO2/H2O; TCD for N2)
- Modified chromatographic detection (column separation with TCD)
- Apparatus requirements: Instruments must ensure complete combustion (oxidant, temperature, time), reduction of nitrogen oxides, removal of interfering species (halides, SOx, O2, CO2, H2O as appropriate), and detectors with linear or appropriately corrected response.
- Reagents: High-purity carrier gas (helium), oxygen and manufacturer-specified reagents/absorbers.
- Calibration and quality control:
- Assemble and calibrate per manufacturer instructions.
- Use at least three calibrating agents spanning expected nitrogen ranges.
- Verify drift, perform periodic control-sample checks and recalibrate if control limits are exceeded.
- Analyses performed in duplicate.
- Calculation: Percent nitrogen (N %) is calculated from detector response (B), calibration response per unit mass (C) and test portion mass (m):
N (%) = (B / C) × (100 / m)
- Precision: Repeatability ~0.11% N (within-lab) and reproducibility ~0.17% N (between-labs) as reported for method validation data.
Applications and who uses it
- Laboratories and quality-control teams in rubber manufacturing, compounding and additives production.
- Materials testing labs performing regulatory, product compliance, R&D and comparative analyses of nitrogen content in elastomers, antioxidants, accelerators and other additives.
- Instrument manufacturers and lab managers implementing or validating automatic analyser setups for nitrogen determination.
Related standards
- ISO/TR 9272:1986 - Determination of precision for test method standards (referenced for precision reporting).
- Prepared by ISO/TC 45 (Rubber and rubber products), SC 2 (Testing and analyses).
Keywords: ISO 15672, total nitrogen, rubber additives, automatic analyser, nitrogen determination, thermal conductivity detection, infrared detection, gas chromatography.