ISO 9647:2020 Steel — Determination of vanadium content — Flame atomic absorption spectrometric method (FAAS)

ISO 9647:2020 Steel — Determination of vanadium content — Flame atomic absorption spectrometric method (FAAS). 5 Reagents During the analysis, unless otherwise specified, use only reagents of recognized analytical grade and only grade 2 water as specified in ISO 3696. 5.1 Pure iron, containing <0,000 5 % of vanadium or of low and known vanadium content. 5.2 Hydrochloric acid, ρ approximately 1,19 g/ml. 5.3 Nitric acid, ρ approximately 1,40 g/ml. 5.4 Perchloric acid, ρ approximately 1,67 g/ml. WARNING — Perchloric acid vapour can cause explosions in the presence of ammonia, nitrous fumes or organic material in general. 5.5 Hydrochloric acid solution, 1 + 50. Add 10 ml of hydrochloric acid (5.2) to 500 ml of water and mix. 5.6 Aluminium solution, 20 g/l. Dissolve 90 g of aluminium chloride hexahydrate (AlCl 3 ·6H 2 O) in about 300 ml of water, add 5 ml of hydrochloric acid (5.2), dilute to 500 ml with water and mix. 5.7 Vanadium standard solution, 2,0 g/l. 5.7.1 Preparation using vanadium metal Weigh (1,000 ± 0,001) g of vanadium (V ≥ 99,9 %) and transfer it into a 400 ml beaker. Add 30 ml of a mixture of three volumes of hydrochloric acid (5.2) and one volume of nitric acid (5.3). Cover with a watch glass and if necessary, heat gently to assist dissolution. When dissolution is complete evaporate the solution to just before dryness and add 20 ml of hydrochloric acid (5.2). Allow to cool to room temperature and transfer the solution quantitatively into a 500 ml one-mark volumetric flask. Dilute to the mark with water and mix. 6 Apparatus All volumetric glassware shall be class A, in accordance with ISO 648 or ISO 1042, as appropriate. Ordinary laboratory apparatus and the following shall be used. 6.1 Atomic absorption spectrometer The spectrometer shall be equipped with a vanadium hollow-cathode lamp and supplied with dinitrogen monoxide and acetylene sufficiently pure to give a steady clear fuel-lean flame, free from water and oil, and free from vanadium. The atomic absorption spectrometer used will be satisfactory if, after optimization according to 8.3.3, the limit of detection and characteristic concentration are in reasonable agreement with the values given by the manufacturer and it meets the performance criteria given in 6.1.1 to 6.1.3. The instrument should also conform to the additional performance requirement given in 6.1.4. 6.1.1 Minimum precision (see Annex C) The standard deviation of 10 measurements of...