ISO INTERNATIONAL STANDARD 7941 First edition 1988-08-01 INTERNATIONALORGANIZATIONFORSTANDARDIZATION ORGANISATIONINTERNATIONALEDENORMALISATION MEKAYHAPOAHAAOPTAHW3ALWANOCTAHAAPTW3ALMM As"inierarLoree Commercial propane and butane - Analysis by gas chromatography Propanesetbutanescommerciaux-Analyseparchromatographieenphasegazeuse Reference number ISO 7941 : 1988 (E) ISO7941 : 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 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. iso collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. 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 7941 was prepared by Technical Committee ISO/TC 28, Petroleumproducts and lubricants. 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 latestedition,unlessotherwisestated. @International OrganizationforStandardization,1988 Printed in Switzerland INTERNATIONAL STANDARD ISO 7941 : 1988 (E) Commercial propane and butane - Analysis by gas chromatography WARNING: Safety precautions -- When testing LPG it is essential to observe suitable safety precautions and any regula- tions applicable to installations, apparatus and storage. Particular attention shall be given to the following. a LPG can cause serious burns from the cold, and the liquid should not be allowed to contact the skin. When sampling LPG, goggles and gloves must be worn. b) Discharge of LPG can give rise to static electricity and it is essential to connect containers to "earth" prior to and during discharge. If hydrogen is used as a carrier gas, special safety precautions shall be taken. More particularly, the hydrogen line shall be carefullytestedforleaks,especiallyintheoven. Scope and field of application 4.2 peak: The portion of the chromatogram recording the detector response while a component is eluted from the This International Standard specifies a gas chromatographic column. method for the quantitative determination of hydrocarbons in liquefied petroleum gas (LPG), excluding components whose 4.2.1 peak area: The area bounded by the peak and the concentrations are below 0,1 % (m/m). It is applicable to the baseline. analysis of propane, butane and their commercial mixtures, which may include saturated and unsaturated C2, C3, C4 and 4.2.2 peak height: The distance between the peak maximum Cs hydrocarbons. It does not apply to "on-line" chroma- andthebaseline. tography. 4.2.3 peak width: The segment of the baseline intercepted 2 References by the tangents drawn at the inflection point of each side of the peak. Iso 565, Test sieves - Woven metal wire cloth, perforated plate and electroformed sheet - Nominal sizes of openings. The peak width at half height is the segment of a line drawn parallel to the baseline at half the peak height which is ISO4257,Liquefiedpetroleumgases-Methodofsampling.1) intercepted by the peak sides. If the baseline is seen to be sloping from the horizontal, both 3Principle measurements are of the projection of these segments onto the horizontal axis. Physical separation by gas chromatography.Identification of thecomponentsbypassingastandardreference mixtureor 4.2.4 peak resolution: The extent to