6636/3 International Standard (TSO INTERNATIONALORGANIZATION FOR STANDARDIZATIONMEKAYHAPOAHAA OPFAHM3AUMA NO CTAHAAPTW3AUMWORGANISATION INTERNATIONALEDENORMALISATION Fruit and vegetable products --- Determination of zinc content Part 3 : Dithizone spectrometric method Produits derives des fruits et legumes -- Détermination de la teneur en zinc -- Partie 3:Methode spectrometriquea la dithizone First edition -- 1983-12-01 ISO 6636/3-1983 (E) UDC 634.1/635.6: 543.42 : 546.47 Ref.No.1SO.6636/3-1983 (E) Price based on 3 pages Foreword ISso (the International Organization for Standardization) is a worldwide federation of national standards bodies (IsO member bodies). The work of developing International Standards is carried out through Iso technical committees. Every member body interested in a subject for which a technical committee has been authorized has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with iso, also take part 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. International Standard ISo 6636/3 was developed by- Technical Committee ISO/TC 34, Agricultural food products, and was circulated to the member bodies in April 1982. It has been approved by the member bodies of the following countries : Austria Kenya Romania Korea, Dem. P. Rep. of South Africa, Rep. of Canada Czechoslovakia Malaysia Spain Germany, F.R. New Zealand Sri Lanka Hungary Peru Tanzania India Philippines Turkey tran Poland USSR Iraq Portugal Yugoslavia The member bodies of the following countries expressed disapproval of the document on technical grounds : Netherlands @ International Organization for Standardization, 1983 Printed inSwitzerland ISO6636/3-1983 (E) INTERNATIONAL STANDARD Fruit and vegetable products - Determination of zinc content: Part 3 : Dithizone spectrometric method Scope and field of application 4.8 Zinc, standard solution corresponding to 500 μg of zinc per millilitre. This part of iso 6636 specifies a dithizone spectrometric method for the determination of the zinc content of fruit and In a 1 000 ml volumetric flask, dissolve 0,500 g of pure vegetable products. granulated zinc in 20 ml of the concentrated hydrochloric acid (4.6), and dilute to the mark with water. 2 Reference 4.9 Zinc, standard solution corresponding to 5 μg of zinc per Iso 5515, Fruits, vegetables and derived products millilitre. Decom- position of organic matter prior to analysis - -Wetmethod. In a 1 000 ml volumetric flask, dilute 10 ml of the standard zinc solution (4.8) to the mark with the 0,04 mol/I hydrochloric acid 3Principle solution (4.10). Prepare this solution at the time of use. Decomposition of organic matter, neutralization of the solution obtained and addition of dithizone (1,5-diphenylthiocarbazone) solution. Extraction of the zinc complex thus formed with 4.10 Hydrochloric acid, 0,04 mol/I solution. chloroform and spectrometric measurement of the absorbance of the extract at a wavelength .of 538 nm. 4.11 1,5-diphenylthiocarbazone (dithizone), solution. Dissolve 0,2 g of dithizone in 100 mi of the chloroform (4.7) 4 Reagents All reagents shall be of recognized analytical quality and, with 4.12 1,5-diphenylthiocarbazone (dithizone), extraction the exception of the standard zinc solutions (4.8 and 4.9), shall solution. in particular, be free from zinc. The water used shall be double distilled water or water of at least equivalent purity. Dilute 1,0 mi of the dithizone solution (4.11) to 100 ml with the chloroform (4.7). 4.1 Sulfuric acid, 25 % (V/V) solution. 4.2 Ammonia, 25 % (V/V) solution. 5 Apparatus 4.3 Phenol red, indicator solution the apparatus used should, therefore, be rinsed with the dithizone solu tion. Dissolve, in a mortar, o,1 g of phenolsulfonephthalein in 2,85 ml of 0,1 mol/1 sodium hydroxide solution and dit