ISO INTERNATIONAL STANDARD 6841 Second edition 1988-06-01 INTERNATIONALORGANIZATION FOR STANDARDIZATION So ORGANISATION INTERNATIONALE DE NORMALISATION MEXKAYHAPOAHAAOPIAHW3ALMAO CTAHAAPTV3ALMM ANs Internat Doc Secr Surface active agents - Technical straight-chain sodium alkylbenzenesulfonates --- Determination of mean relative molecular mass by gas-liquid chromatography Agents de surface - Alkylbenzene sulfonates de sodium lineaires techniques Determination de la masse moleculaire relative moyenne par chromatographie gaz-liquide Referencenumber ISO 6841 :1988 (E) Copyright Inter Standardizatior No reproduction or networking permitted without license from IHS Not for Resale ISO 6841 : 1988 (E) 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 therightto be represented onthat committee.International organizations,govern- mental and non-governmental, in liaison with Iso, also take part in the work. ISo col- laboratescloselywiththeInternational Electrotechnical Commission(IEC)onall mat ters of electrotechnical standardization. Draft International Standards adopted by thetechnical 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 6841 was prepared by Technical Committee ISO/TC 91, Surface active agents. This second edition cancels and replaces the first edition (ISO 6841 : 1983), of which it constitutesaminorrevision. International Organization for Standardization, 1988 Printed in Switzerland Copyright International Organization for Standardization No reproduction or networking permitted without license from IHS Not for Resale ISO 6841 : 1988 (E) Introduction When using the two-phase titration for the determination of anionic active matter con- tent, it is necessary toknow the mean relative molecular mass of the substance. Anaccurate and rapid method consistsof determining bygas-liquid chromatography (GLC) the mean relative molecular mass of the alkylbenzene used to manufacture the monosulfonated products; the relative molecular mass of the respective monosul- fonate or monosulfonic acid canthen be calculated by adding the relative molecular mass of the SOgNa group minus Na, or that of the SOgH group minus H. The GLC technique is only applicable to straight-chain alkylbenzenes, since branched- chain types will give chromatograms from which it is impossible to identify and to calculate the relative molecular mass for individual chains. NOTE - Any ortho-fused polycyclic hydrocarbon derivatives of low relative molecular mass pre sent, such as indan, and tetrahydronaphthalene, as well as branched-chain alkyibenzenes, are not taken into account in the calculation of the relative molecular mass of the technical straight- chainsodiumalkylbenzenesulfonate analysed. Copyright International Organization for Standardization ii No reproduction or networking permitted without license from IHS Not for Resale