ISO 11021 pdf download

ISO 11021 pdf download.Essential oils — Determination of water content — Karl Fischer method 1 Scope This International Standard specifies a method for the determination of the water content of essential oils by the Karl Fischer method. 2 Normative reference The following normative document contains provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, this publication do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 760, Determination of water content — Karl Fischer method (General method). 3 Terms and definitions For the purposes of this International Standard, the following term and definition apply. 3.1 water content amount of water present in the essential oil considered, determined in accordance with the procedure specified in this International Standard NOTE Water content is expressed as a mass fraction in percent [formerly designated as % (m/m)]. 4 Principle The water present in a test portion is absorbed with dried methanol. The water is allowed to react with the Karl Fischer reagent without pyridine, previously standardized by titration using a Karl Fischer apparatus. The endpoint of the reaction is obtained by an electrometric method. 5 Reactions During the determination of water according to the Karl Fischer method, the water present in the sample reacts, in the presence of an amine and an alcohol, with iodine and sulfur dioxide: H 2 O + I 2 + SO 2 + ROH + 3R n NH 3–n → 2R n NH 3–n HI + R n NH 3–n HSO 4 R where R is an alkyl or alkoxyl group. The endpoint of the reaction is obtained electrometrically by a surplus of iodine. 6 Reagents and materials Use only reagents of recognized analytical quality and distilled or demineralized water or water of equivalent purity. 6.1 Methanol, containing not more than 0,05 % of water by mass. If the reagent contains more than this quantity of water, dry it by distillation in an inert atmosphere (nitrogen, helium etc.) with magnesium turnings activated with iodine. Collect the distillate in a flask protected from atmospheric moisture by means of a guard tube...