ISO 20921:2019

ISO 20921:2019 pdf free.Textiles – Determination of stable nitrogen isotope ratio
in cotton fibres.
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:
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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.
3.2 isotope-ratio mass spectrometry IRSM specialization of mass spectrometry, in which mass spectrometric methods are used to measure the relative abundance of isotopes in given sample
Note 1 to entry: The analysis of isotopes is normally related to measuring isotopic variations caused by mass-dependent isotopic fractionation in natural systems.
3.3 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. lsotopic 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.
7 Preparation 7.1 Sampling of test specimen Cotton fibre samples are taken from fabricated textiles and prepared as test specimens. 7.2 Pre-treatment of test specimen Cotton fibre samples are immersed with 100 ml distilled waters for 3 min and oven-dried at 80 °C for 24 h. Dried samples are chopped, homogeneously ground into a very fine powder using a ball-mill and used in triplicate for 15N analysis. 8 Test procedure 8.1 Weighing of aliquot 8.1.1 Determination of weighing amount needed Each finely ground test specimen is weighed with a tin capsule (or can) using a microbalance
(readability: at least 1 μg). Provide between (100 ~1 200] μg of nitrogen for each aliquot of the test specimen to meet EA-IRMS detection limits. However, the minimum amount needed for accurate and precise analysis of δ15N is typically about 100 ug of nitrogen. 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) % itrogen. Turn on the microbalance and wait for the microbalance to stabilize. Use the tweezer to grab an empty tin capsule by the edge and place on top of the balance. Push the“TARE” button to re-zero the mass. Carefully scoop out a small aliquot of test specimen into the tin capsule by adding in small increments. Remove the tin capsule from the microbalance. Fold the tin capsules several times into a small cube or sphere with the tweezers to make sure the openings are closed.  Place the cube into your sample tray such as 96-well tray for delivery or shipping. Clean the spatula between each weighing to avoid contamination.ISO 20921 pdf download.

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