ASTM_D_7847_-_12e1.pdf

Designation:D7847121Standard 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.1NOTESubsection 1.2 and Section 4 were corrected editorially in March 2015.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,two microbiological Methods have been approved by ASTM:Method D7463 and Method D7687.Although both methods measure adenosine triphosphate(ATP)infuel and fuel-associated water samples the method of obtaining the sample differs;ASTM D7463 usesa liquid to liquid extraction whereas ASTM D7687 uses filtration.Because these methods measure the concentration of a biomarker molecule,the issues that arerelevant to ILS are similar to,but somewhat different than those that affect ILS for culture methods.Beckers2investigated microbiological test method ILS,but advised several measures that are eitherimpractical for or not relevant to the methods that have been developed within D02:(1)Freezeinoculated samples after dispensing into portions for shipment to participating labs;(2)Use a singleorganisms challenge;(3)Add the challenge microbe to a sample matrix in which it is likely toproliferate.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.Scope1.1 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 microbial1This 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 Dec.1,2012.Published January 2013.DOI:10.1520/D7847-12E01.2Beckers,H.J.,“Precision Testing of Standardized Microbiological Methods,”Journal of Testing and Evaluation,JTEVA,Vol.14,No.6,November 1986,pp.318-320.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 contamination in fuels,lubricants and similar low water-content(water activity 0.8)fluids.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.2.Referenced Documents2.1 ASTM Standards:3D156 Test Method for Saybolt Color of Petroleum Products(Saybolt Chromometer Method)D1129 Terminology Relating to WaterD4012 Test Method forAdenosine Triphosphate(ATP)Con-tent of Microorganisms in WaterD4175 Terminology Relating to Petroleum,Pet