6636/1 International Standard (TSO Fruits, vegetables and derived products -- Determination of zinc content Part 1 : Polarographic method Fruits, legumes et produits derives - Détermination de la teneur en zinc - Partie 1 : Methode polarographique First edition - 1986-04-15 6636/1-1986 (E) UDC 635.1/.6:543.253:546.47 Ref. No.ISO 6636/1-1986 (E) Descriptors : agricultural products, fruits, vegetables, fruit and vegetable products, chemical analysis, determination of content, zinc, polarographic methods. iso Price based on 3 pages Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (Iso member bodies). The work of preparing International Standards is normally carried out through isO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with IsO,also takepart in the work. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISO Council. They are approved in accordance with ISO procedures requiring at least 75% approval by the member bodies voting. International Standard ISO 6636/1 was prepared by Technical Committee ISO/TC 34, Agriculturalfoodproducts. Users should note that all International Standards undergo revision from time to time and that any reference made herein to any other International Standard implies its latest edition, unless otherwise stated. International Organization for Standardization, 1986 Printed in Switzerland ISO6636/1-1986 (E) INTERNATIONAL STANDARD Fruits, vegetables and derived products Determination of zinc content : Part 1 : Polarographic method 1 Scope and field of application 4.6 Zinc, standard solution corresponding to 0,01 to 0,04 mg of Zn per millitre. This part of Iso 6636 specifies a polarographic method for the determination of the zinc content of fruits, vegetables and 4.6.1 Stock solution derived products. Dissoive 1 g of metallic zinc [purity at least 99 % (m/m)] in NOTE -- ISO 6636/2 specifies an atomic absorption spectrometric 10 ml of the hydrochloric acid (3.2) in a conical flask. Transfer method,and iSO6636/3a dithizone spectrometric method. quantitatively to a 1 000 ml one-mark volumetric flask, make up to the mark with water and mix. Copper, tin, lead and cadmium do not interfere with the deter. mination. 4.6.2 Preparation Dilute 1 to 4 ml of the zinc stock solution (4.6.1) to the mark 2 Reference with water in a 100 ml one-mark volumetric flask and mix. Iso 874, Fresh fruits and vegetables -- Sampling. 5 Apparatus 3Principle Usual laboratory equipment and in particular Ashing of a test portion in a muffle furnace at 525 ± 25 oC. Treatmentof the ash obtainedwithhydrochloricacid 5.1 Polarograph, suitable for determining zinc contents Neutralizationwith25%(m/m)ammoniasolutionanddeter greater than 0,05 mg/kg, provided with a mercury-dropping mination of the zinc content by polarography using an electrode as the cathode and an electrolyser with mercury at ammonia/ammonium chioride electrolyte. the bottom as the anode. 5.2 Drying oven, capable of being maintained at 100 to 4 Reagents 150 oc within a tolerance not exceeding ± 5 °C. All reagents shall be of recognized analyticai grade and the 5.3 Muffle furnace, capable of being maintained at 100 to water used shall be distilled water or water of at least equivaient 700 oC within a tolerance not exceeding ± 25 °C. purity. 5.4 Porcelain dishes, of diameter 9 to 11 cm. 4.1 Nitric acid (α20 = 1,38 g/ml). 4.2 Hydrochloric acid, diluted 1 + 1. 5.5 One-mark volumetric flask, of capacity 50 ml. Dilute 1 part by volume of hydrochloric acid (α20 = 1,19 g/ml) 5.6 Graduated pipettes, of capacities 1 and 10 ml. with 1 part by volume of water. 5.7 Conical flask, of capacity 25 ml