6557/1 (ISO nternational Standard INTE RNATIONAL ORGANIZATION FOR STANDARDIZATION ME XAYHAPOAHAR OPrAHW3ALMA nO CTAHAAPTW3AuWW-ORGANISATION INTE RNATIONALE DE NORMALISATION Fruits, vegetables and derived products - Determination of ascorbic acid - Part 1 : Reference method Fruits, legumes et produits derives - Determination de la teneur en acide ascorbique - Partie 1: Methode de reference First edition -- 1986-10-01 UDC 635.1/.6 : 543.426 : 547.475.2 Ref. No. 1ISO 6557/1-1986 (E) Descriptors : agricultural products, fruits, vegetables, fruit and vegetable products, chemical analysis, determination of content, ascorbic acid, spectrochemical analysis. Price based on 3 pages d without license from IHS Not for Resale 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 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. They are approved in accordance with ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard ISO 6557/1 was prepared by Technical Committee iSO/TC 34, Agricultural food products. 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 adadz Not for Resale ISO 6557/1-1986 (E) INTERNATIONAL STANDARD Fruits, vegetables and derived products -- Determination of ascorbic acid Part 1: Reference method 1 Scope and field of application 3 Reagents and materials All reagents shall be of recognized analytical grade and the This part of ISO 6557 specifies the reference method, using water used shall be distilled or water of equivalent purity. molecular fluorescence spectrometry, for the determination of the combined ascorbic and dehydroascorbic acid content of 3.1 o-Phenylenediamine dihydrochloride fruits, vegetables and derived products. (CgHgN2 : 2HCI), 0,2 g/I solution. Prepare this solution just before use. Principle 3.2 Sodium acetate trihydrate (CH3COONa-3H20), Transformation of ascorbic acid into dehydroascorbic acid 500 g/1 solution. using activated charcoal. 3.3 Boric acid/sodium acetate solution. Reaction of the dehydroascorbic acid obtainedwith 0-phenylenediamine (OPDA) to give a fluorescent compound Dissolve 3 g of boric acid (HgBO3) in 100 ml of the sodium according to the reaction acetate solution (3.2). Prepare this solution just before use. 3.4 Ascorbic acid, 1 g/l standard solution. ZHN 0 Weigh, to the nearest 0,01 mg, 50 mg of ascorbic acid, CH(OH)CH2OH previously dehydrated in a desiccator protected from light. NH2 Transfer quantitativelytoa 50 mlone-markvolumetricflask and 0 (Dehydroascorbic acid) make up to the mark with the extraction solution (3.5), just (OPDA) before use. 3.5 Extraction solution. 3.5.1 Metaphosphoric acid/acetic acid. Transfer 30 g of metaphosphoric acid (HPO3) to a 1 000 ml beaker or conical flask containing 80 ml of glacial acetic acid CH(OH)CH20H (CHgCOOH) and about 500 ml of water. Warm and stir gently until complete dissolution. (1-Oxo-2,4 H-3-(1,2-dihydroxyethyl) furo [3,4-b] quinoxaline) Allow the solution to cool. Transfer it quantitatively to a 1 000 ml one-mark volumetric flask and make up to the mark with water. 10 In a control test in the presence of boric acid, formation of the complex H3BO3-dehydroascorbic acid to prevent react