ISO 1656:2019

Name: ISO 1656:2019 — Rubber, raw natural, and rubber latex, natural — Determination of nitrogen content
SKU: ISO 1656:2019
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Rubber, raw natural, and rubber latex, natural — Determination of nitrogen content

Название (английский):

ISO 1656:2019

Rubber, raw natural, and rubber latex, natural — Determination of nitrogen content

Статус документа:: Действующий
Формат:: Электронный (PDF)
Количество страниц:: 21
Дата публикации:: 30 июля 2019 г.
Издание:: ISO IS 1656 edition 5 version 1
ICS:: 83.040.10

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Описание (английский):

This document specifies a macro-method and a semi-micro method for the determination of nitrogen in raw natural rubber and in natural rubber latex using variants of the Kjeldahl process. NOTE The determination of nitrogen in natural rubber is usually carried out in order to arrive at an estimate of the protein content. Minor amounts of non-proteinous nitrogen containing constituents are also present. However, in the dry solids prepared from natural rubber latex, these materials can make a substantial contribution to the total nitrogen content.

Abstract

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Стандарты, упомянутые в описании

Overview

ISO 1656:2019 - Rubber, raw natural, and rubber latex, natural - Determination of nitrogen content - specifies two validated analytical procedures (a macro-method and a semi‑micro method) for measuring nitrogen content in raw natural rubber and natural rubber latex. Both methods are variants of the Kjeldahl process: sample digestion with sulfuric acid and a catalyst, alkaline distillation of ammonia, and quantification by absorption/titration. The determination is commonly used to estimate protein content in natural rubber; non‑protein nitrogenous constituents may also contribute to total nitrogen, especially in latex dry solids.

Key topics and technical requirements

Scope and principle: Conversion of organic nitrogen to ammonium sulfate by acid digestion, followed by distillation and titration of liberated ammonia.

Two methods: Detailed procedures for macro and semi‑micro Kjeldahl variants to suit different sample sizes and laboratory capacities.

Catalyst options: Recommended non‑toxic titanium dioxide/copper sulfate/potassium sulfate mixture (TiO2/CuSO4/K2SO4) as an alternative to selenium‑based catalysts, improving safety and environmental impact.

Reagents and standardization: Preparation and standardization of reagents (sulfuric acid, boric acid, sodium hydroxide, standard volumetric solutions) and indicators.

Apparatus and sampling: Requirements for Kjeldahl digestion and distillation apparatus; sampling/preparation referenced to ISO 1795 (raw rubber) and ISO 123 / ISO 124 (latex sampling and total solids).

Procedure elements: Digestion, blank tests, ammonia absorption options (standard sulfuric acid or boric acid followed by titration), expression of results, and reporting.

Precision and validation: Precision data and inter‑laboratory test (ITP) validation are provided; method revision emphasizes repeatability and safety.

Applications and users

Quality control laboratories in rubber manufacturing and raw material supply chains - for routine nitrogen/protein estimation in raw rubber and latex.

Production and procurement teams - to verify incoming raw natural rubber specifications and assess protein-related properties.

Research and development - material characterization, formulation studies, and comparative analyses of natural rubber batches.

Regulatory and certification bodies - for standardized reporting of nitrogen/protein levels in compliance and specification documents.

Environmental and safety-focused labs - benefitting from the selenium‑free catalyst option that reduces hazardous waste and operator exposure.

Related standards

ISO 123 - Rubber latex - Sampling

ISO 124 - Latex, rubber - Determination of total solids content

ISO 1795 - Rubber, raw natural and raw synthetic - Sampling and further preparative procedures

ISO 1656:2019 is essential for laboratories seeking a standardized, validated Kjeldahl method tailored to natural rubber and latex, balancing analytical accuracy with improved safety through non‑toxic catalyst recommendations. Keywords: ISO 1656:2019, Kjeldahl process, nitrogen determination, natural rubber, rubber latex, protein content, titanium dioxide catalyst, analytical method.

ISO 1656:2019

Abstract

Похожие стандарты

Overview

Key topics and technical requirements

Applications and users

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