BS ISO 23637:2021 pdf download – Cereals — Determination of cadmium content by graphite furnace atomic absorption spectrometry with diluted nitric acid extraction This document specifies a method for the determination of cadmium (Cd) in cereals. It is applicable to rice, brown rice, wheat and maize by graphite furnace atomic absorption spectrometry (GFAAS) after extraction with diluted nitric acid (HNO 3 ). The limit of quantification is 0,002 mg/kg; it is approximate and dependent on the sample matrix as well as on the instrument conditions. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3696, Water for analytical laboratory use — Specification and test methods 3 No terms and definitions are listed in this document. 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 https://www.electropedia.org/ 4 Principle Cadmium (Cd) is extracted from the cereals using diluted nitric acid and then determined by graphite furnace atomic absorption spectrometry (GFAAS). 5 Reagents and solution During the analysis, unless otherwise stated, use only reagents of recognized analytical purity and only water of grade 1 in accordance with ISO 3696. 5.1 Nitric acid (HNO 3 ), not less than 65 % (mass fraction) of approximately ρ(HNO 3 ) = 1,4 g/ml. 5.2 Nitric acid solution (0,5 %, volume fraction), mix 0,5 volume parts of HNO 3 (5.1) and 100 ml volume parts of water. 5.3 Nitric acid solution (50 %, volume fraction), mix HNO 3 (5.1) and water in equal volume. 5.4 Palladium nitrate hydrate (Pd(NO 3 ) 2 , 99,9 % purity). 7.3 Preparation of the test samples Grind the laboratory sample using a grinding mill (6.1) until it passes through the sieve (6.6) and mix thoroughly. The particle size of the maize and its milling products should be less than 0,25 mm. The particle size of other cereal varieties should be less than 0,40 mm. 7.4 Extraction 7.4.1 General Weigh 0,200 g ± 0,001 g (m) of the sample flour into a 10 ml plastic centrifuge tube, and add 5,0 ml of diluted nitric acid (5.2). Close the centrifuge tube tightly and...
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