DIN ISO 20369:2012-10

The International Standard ISO 20369 has been published in July 2009 as a result of consultations at ISO/TC 126 "Tobacco and tobacco products" (secretariat: Germany) on the determination of the citrate content of material used to produce wrappings for cigarette filters, cigarettes and other tobacco products. The standardization project has been submitted by Germany and is based on the International Standard DIN 10259. Working Committee NA 057-04-01 AA "Tabak und Tabakerzeugnisse" ("Tobacco and tobacco products") of the Food and Agricultural Products Standards Committee (NAL) at DIN decided to transfer ISO 20369 into the German body of standards. The working committee made its decision in particular from the point of view of a necessary harmonization of the international and national standards in the field of tobacco and tobacco products. This standard specifies a method for the determination of the citrate content of material used to produce wrappings for cigarette filters, cigarettes and other tobacco products. The citrate content is determined by an enzymatic method. During the process citrate (citric acid), catalysed by the enzyme citrate lyase, is first converted to oxaloacetate and acetate. In the presence of the enzymes L-malate dehydrogenase and L-lactate dehydrogenase, oxaloacetate and its decarboxylation product, pyruvate, are converted by reduced nicotinamide adenine dinucleotide (NADH) to L-malate and L-lactate, respectively. The amount of oxidized NADH is proportional to the amount of citrate. The residual NADH is determined from its absorbance at 340 nm by spectrophotometry. The standard supersedes DIN 10259:1998-06. With respect to this standard a warning note has been included and the normative references have been updated. The absorption wavelength has been specified to be 340 nm; furthermore an example of a suitable product for reagent mixtures and filter paper has been included. Conditioning is now to be in accordance with ISO 187 instead of DIN EN 20187; the determination of the moisture content is now to be in accordance with ISO 287 instead of DIN EN 20287 (unchanged procedures). The result is reported as a percentage by mass of anhydrous citric acid instead of citric acid monohydrate. Furthermore the standard has been editorially revised and brought in line with the current rules of presentation. The committee responsible for this standard is NA 057-04-01 AA "Tabak und Tabakerzeugnisse" ("Tobacco and tobacco products") at DIN.