Overview
ISO 19051:2015 specifies a laboratory test method for determining nitrogen content in raw natural rubber and natural rubber latex using the Micro Dumas combustion method. The Micro Dumas approach is a rapid elemental combustion technique that converts sample nitrogen to gaseous forms, reduces oxides to N2, and quantifies nitrogen using gas detection (e.g., GC-TCD or infrared/TCD cells). Compared with Kjeldahl, the method is faster, safer and more environmentally friendly and is suitable for routine quality control and research.
Key topics and technical requirements
- Scope: Applicable to raw natural rubber (solid) and natural rubber latex (dried prior to analysis).
- Principle: High‑temperature combustion (~1 000 °C) in oxygen with helium carrier gas; oxides of nitrogen reduced to N2 over heated copper (~600 °C) and quantified.
- Gases & purity: Helium and oxygen, both typically 99.99% purity to minimize nitrogen blank.
- Sample preparation:
- Solids: laboratory sample per ISO 1795; cut to small pieces.
- Latex: sample per ISO 123; typically dried (110 °C vacuum oven or 70 °C) to a test piece.
- Test piece mass: Typical test pieces in the range 0.50 mg to 1.50 mg (microbalance to 0.00001 g recommended); representative analyses for natural products may require larger sample sizes (up to ~1 g or more).
- Instrumentation & setup:
- Combustion elemental analysers with sample introduction (tin capsules, vials, or autosampler).
- Typical furnace and GC/TCD operating parameters are provided (carrier flow, run time, furnace temperatures).
- Calibration & quality control:
- Blank runs to establish instrument baselines and nitrogen blank.
- K‑Factor and multi‑point calibration using certified micro‑analytical standards (amino acids, urea, etc.).
- Calibration schedule and inspection per Annex A.
- Reporting: Sample description, preparation method, full reference to ISO 19051, test procedure, number of test pieces, mean results and dates.
Applications and who uses it
- Quality control laboratories in rubber manufacturing to monitor nitrogen/protein content and grade consistency (raw rubber, skim rubber, latex grades).
- Analytical and testing laboratories performing routine elemental analysis of rubber materials.
- Research institutions studying protein content, processing effects, or material characterization.
- Certification bodies and purchasers requiring standardized test data for specifications and acceptance.
Related standards
- ISO 123 - Rubber latex - Sampling
- ISO 124:2014 - Latex, rubber - Determination of total solids content
- ISO 1795 - Raw rubber sampling and preparative procedures
- ISO 18899:2013 - Calibration of test equipment
Keywords: ISO 19051:2015, Micro Dumas combustion method, nitrogen content, natural rubber, rubber latex, elemental analysis, calibration, quality control.