BS ISO 20921:2019 pdf free.Textiles – Determination of stable nitrogen isotope ratio in cotton fibres.
BS ISO 20921 1 Scope This document specifies the determination of the ratio of nitrogen isotopes in cotton fibres that are used for textile production. It applies not only to cotton textiles but also to raw cotton taken from cotton fields. 2 Normative references There are no normative references in this document. 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses:ISO Online browsing platform: available at https://www.iso.org/obp IEC Electropedia: available at http://www.electropedia.org/ 3.1 stable isotope atom whose nucleus contains the same number of protons but a different number of neutrons Note 1 to entry: Stable isotopes do not decay into other elements, while radioactive isotopes are unstable and will decay into other elements.isotopic fractionation isotopic discrimination process that affect the relative abundance of isotopes Note 1 to entry: Normally, the focus is on stable isotopes (3.1) of the same element. Isotopic fractionation in the natural environment can be measured by isotope analysis, using isotope-ratio mass spectrometry, to separate different element isotopes on the basis of their mass-to-charge ratios. Note 2 to entry: Both heavy and light stable isotopes participate freely in biochemical reactions and in geochemical processes, but the rate at which heavy and light stable isotopes react differs. As a result, the lighter isotopes react faster than the heavier isotopes leading to isotopic fractionation between reactant and product in the reactions.For example, if the test specimen has 1 % nitrogen and 100 μg of nitrogen for the IRMS measurements is provided, then an aliquot that weighs 10 mg shall be prepared. For samples with unknown % nitrogen, it is recommended to determine the % nitrogen of the test specimen before making isotope analysis. In general, the optimal mass of an aliquot for the IRMS measurements is 33 mg to 56 mg for cotton products (cotton fibres in yarns or textiles), since cotton products typically contain between 0,18 and 0,30) % nitrogen.BS ISO 20921 pdf download.