BS ISO 20921:2019 pdf free

BS ISO 20921:2019 pdf free.Textiles – Determination of stable nitrogen isotope ratio in cotton fibres
Continuous-type EA-IRMS is used for the determination of 15N in a gas sample that is introduced into IRMS through the elemental analyser (EA). The EA-IRMS is equipped with an ion-source for ionizing the incoming sample gases, a permanent magnet and an electromagnet for steering the ions, and the Faraday cups collecting N2 gas travelling with the different mass-to-charge ratios.The isotopic nitrogen composition of the sample gas is compared to that of standard gas (atmospheric N2) during each sample run, and the resulting sample’s 815N value is calculated using Formula (1).
a) Place packed tin capsules continuously into a carousel (auto-sampler unit) for automatic analysis.
b) Drop packed tin capsules sequentially into the oxidation reactor (980 approximately 1 080)°C and then combust them with excess 02 to complete oxidation.
c) Perform EA-IRMS measurements and check the isotopic nitrogen composition of gas relative to that of the standard gas (atmospheric N2) from a compressed cylinder with known or predetermined isotope ratio at every measurement.
d) During each run, check the precision of isotope analysis with an internationally accepted reference material.
Sampling of soil (test specimen 2) at harvest time is mandatory particularly at the early identification of cotton fibres; otherwise, can be omitted. In each cotton field, at least two composite soil samples were randomly collected in 1 000 m2. Each composite soil sample was made using five sub-samples taken individually from five root zones (10 cm approximately 30 cm) around each representative crop chosen.Sample size could vary depending on soil heterogeneity, crop history, fertilization history, and so forth.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.
Soil (test specimen 2) samples are oven-dried at 105 °C for 24 h, passed through a 2 mm sieve before grinding. Dried samples are homogeneously ground into a very fine powder using a ball-mill.BS ISO 20921 pdf free download.