BS ISO 19051:2015 pdf download

BS ISO 19051:2015 pdf download.Rubber, raw natural, and rubber latex, natural — Determination of nitrogen content by Micro Dumas combustion method
1 Scope
This International Standard specifies a test method for the determination of nitrogen content of raw natural rubber using the Micro Dumas combustion method. This method is also applicable to natural rubber latex.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 123, Rubber latex — Sampling
ISO 124:2014, Latex, rubber — Determination of total solids content
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
ISO 18899:2013, Rubber — Guide to the calibration of test equipment
3 Principle
In the combustion process (furnace at ca. 1 000 °C), nitrogen is converted to nitrogen gas/oxides. If other elements are present, they will also be converted to different combustion products. A variety of absorbents are used to remove these additional combustion products.
The combustion products are swept out of the combustion chamber by an inert carrier gas such as helium and passed over heated (about 600 °C) high purity copper. This copper can be situated at the base of the combustion chamber or in a separate furnace. The function of this copper is to remove any oxygen not consumed in the initial combustion and to convert any oxides of nitrogen to nitrogen gas.The gases are then passed through the absorbent traps.
Detection of the gases can be carried out in a variety of ways, including the following:
a) GC separation followed by quantification using thermal conductivity detection;
b) partial separation by GC (“frontal chromatography”) followed by thermal conductivity detection;
c) series of separate infrared and thermal conductivity cells for detection of individual compounds.
5 Apparatus
5.1 Combustion elemental analysers are manufactured in a variety of configurations to suit specific applications and the choice will depend on the elements of interest, the sample type and size, and the concentration of the analyte. All instruments require two gas supplies: an inert carrier gas (helium recommended) and high purity oxygen (minimum 99,99 %). The strict specification for oxygen and the carrier gas is associated with the need to reduce the nitrogen “blank” contribution to an inconsequential level. Additionally, GC-type gas filters are also usually fitted to prevent trace organic species and water entering the combustion system. The choice of test piece introduction system will depend on the application and the nature of the material. For solids or viscous liquids, the test pieces are weighed out into tin capsules. For liquids, the test pieces can be sealed in individual aluminium vials or introduced through a liquid auto-sampler.