(ISO International Standard 6637 INTE RNATIONAL ORGANIZATION FOR STANDARDIZATION MEXAYHAPOAHAA OPrAHW3ALWR nO CTAHAAPTW3AUNW+ORGANISATION INTE RNATIONALE DE NORMALISATION Fruits, vegetables and derived products -- Determination of mercury content -- Flameless atomic absorption method Fruits, legumes et produits derivés -- Détermination de la teneur en mercure - Méthode par absorption atomique sans flamme First edition - 1984-06-01 UDC 634.1/635.6 : 543.422 : 546.49 Ref. No. ISO 6637-1984 (E) 06637-1984 (E) Descriptors : food products, fruit and vegetable products, tests, determination of content, mercury, atomic absorption spectroscopic method. Price based on 5 pages Not for Resale Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (iSO member bodies). The work of developing International 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 6637 was developed by Technical Committee ISO/TC 34, Agricultural food products, and was circulated to the member bodies in August 1982. It has been approved by the member bodies of the following countries : Australia Iran Philippines Austria Ireland Poland Israel Romania Canada Kenya Czechoslovakia South Africa, Rep. of Egypt, Arab Rep. of Korea, Dem. P. Rep. of Spain Tanzania Ethiopia Korea, Rep. of Turkey France Malaysia Germany, F. R. USA Mexico Hungary Netherlands USSR India New Zealand Yugoslavia No member body expressed disapproval of the document. International Organization for Standardization, 1984 Printed in Switzerland Copyright Internatinal Organization for Standardization Not for Resale cense from IHS INTERNATIONAL STANDARD ISO 6637-1984 (E) Fruits, vegetables and derived products - Determination of mercury content - Flameless atomic absorption method 1 Scope and field of application 4 Apparatus This International Standard specifies a method for the determi- The glassware used shall be washed beforehand with hot con- nation of the mercury content of fruits, vegetables and derived centrated nitric acid and rinsed with water. products. Usual laboratory equipment, and 2 Principle 4.1 Mechanical grinder, the internal lining and blades of which are of polytetrafluoroethylene (PTFE). Decomposition of organic matter in a sulfuric-nitric acid medium. Reduction of mercury(ll) to metallic mercury by the action of tin(ll) chloride. Entrainment of the mercury vapour by 4.2 Decomposition apparatus (see figure 1). absorption in an enclosed apparatus The apparatus is made of borosilicate glass and comprises four elements joined by conical ground joints, as follows: 3 Reagents a) Element (A) is a modified Soxhlet extractor of capacity 200 ml, fitted with a stop-cock and a side tube linking this All the reagents shall be of recognized analytical quality and element directly to the round-bottomed flask (D); shall,withtheexceptionofthestandardmercurychloridesolu b) Element (B) is a dropping funnel of capacity 75 ml, fit- tions (3.6 and 3.7), be free from mercury. The water used shall ted to the second neck of the round-bottomed flask (D); be distilled water free from mercury, or water of equivalent purity. c) Element (C) is a condenser 35 cm long, fitted to the top of the Soxhlet extractor (A); 3.1 Sulfuric acid (020 = 1,84 g/ml). d) Element (D) is a round-bottomed flask, of capacity 500 ml, fitted below the Soxhlet extractor (A), and in the Nitric acid (g20 = 1,38 g/ml). 3.2 second neck (30 mm from the first neck) of which is fitted the dropping funnel (B). 3.3 Nitric acid, 5 % (V/ V) solution. When the stop-cock of the Soxhlet e