ASTM_D_7847_-_17.pdf

Designation:D784717Standard Guide forInterlaboratory Studies for Microbiological Test Methods1This standard is issued under the fixed designation D7847;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.INTRODUCTIONMicrobiological parameters present a number of unique challenges relative to chemical and physicaltest methods apropos of the development of precision and bias terms.A number of these challengesare discussed in Guide E1326.As a working group(WG)we first grappled directly with some of theseissues during the development of Practice D6974.The drafts balloted at the D02.14 subcommitteelevel in February and June 2002,were balloted with the document identified as a Method.Moreover,the proposed Method was drafted as a harmonized document with the Energy Institutes(EI)MethodIP 385.When the item was balloted at D02 level,members of D02.94 compelled us to change the titlefrom Method to Practice.The argument was that ASTM Methods list single series of steps that leadto a measurable result(a bit of data;quantitative,semi-quantitative or qualitative).Because D6974provides for the selection of different sample volumes(based on the estimated culturable populationdensity)and different growth media(based on the sub-population to be quantified),it would only beaccepted as an ASTM Practice;not a Method.This issue of performing interlaboratory studies forculture methods will be discussed below.Since Practice D6974 was approved,four microbiological test methods have been approved byASTM:D7463,D7687,D7978,and D8070.Because these methods measure the concentration of a biomarker molecule or microorganisms,theissues that are relevant to ILS are similar to,but somewhat different than those that affect ILS forculture methods.Beckers2investigated microbiological test method interlaboratory studies,butadvised several measures that are either impractical for or not relevant to the methods that have beendeveloped within D02:(1)Freeze inoculated samples after dispensing into portions for shipment toparticipating labs;(2)Use a single organisms challenge;(3)Add the challenge microbe to a samplematrix in which it is likely to proliferate.This guide will list key issues that must be addressed when designing ILS for Methods intended tomeasure the microbial properties of fuels and fuel-associated waters.1.Scope*1.1 Microbiological test methods present challenges that areunique relative to chemical or physical parameters,becausemicrobes proliferate,die off and continue to be metabolicallyactive in samples after those samples have been drawn fromtheir source.1.1.1 Microbial activity depends on the presence of avail-able water.Consequently,the detection and quantification ofmicrobial contamination in fuels and lubricants is made morecomplicated by the general absence of available water fromthese fluids.1.1.2 Detectability depends on the physiological state andtaxonomic profile of microbes in samples.These two param-eters are affected by various factors that are discussed in thisguide,and contribute to microbial data variability.1.2 This guide addresses the unique considerations thatmust be accounted for in the design and execution of inter-laboratory studies intended to determine the precision ofmicrobiological test methods designed to quantify microbialcontamination in fuels,lubricants and similar low water-content(water activity 0.8)fluids.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.14 on Stability and Cleanliness of Liquid Fuels.Current edition approved June 1,2017.Published June 2017.Originallyapproved in 2012.Last previous edition approved in 2012 as D7847 121.DOI:10.1520/D7847-17.2Beckers,H.J.,“Precision Testing of Standardized Microbiological Methods,”Journal of Testing and Evaluation,JTEVA,Vol.14,No.6,November 1986,pp.318320.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognize