ASTM D7847-22

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7847 − 22
Standard Guide for
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Interlaboratory Studies for Microbiological Test Methods
This standard is issued under the fixed designation D7847; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Microbiologicalparameterspresentanumberofuniquechallengesrelativetochemicalandphysical
test methods apropos of the development of precision and bias terms. A number of these challenges
are discussed in Guide E1326.As a working group (WG) we first grappled directly with some of these
issues during the development of Practice D6974. The drafts balloted at the D02.14 subcommittee
level 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 Institute’s (EI) Method
IP385.When the item was balloted at D02 level, members of D02.94 compelled us to change the title
from Method to Practice. The argument was that ASTM Methods list single series of steps that lead
to a measurable result (a bit of data; quantitative, semi-quantitative or qualitative). Because D6974
provides for the selection of different sample volumes (based on the estimated culturable population
density) and different growth media (based on the sub-population to be quantified), it would only be
accepted as an ASTM Practice; not a Method. This issue of performing interlaboratory studies for
culture methods will be discussed below.
Since Practice D6974 was approved, four microbiological test methods have been approved by
ASTM: D7463, D7687, D7978, and D8070.
Because these methods measure the concentration of a biomarker molecule or microorganisms, the
issues that are relevant to ILS are similar to, but somewhat different than those that affect ILS for
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culture methods. Beckers investigated microbiological test method interlaboratory studies, but
advised several measures that are either impractical for or not relevant to the methods that have been
developed within D02: (1) Freeze inoculated samples after dispensing into portions for shipment to
participating labs; (2) Use a single organisms challenge; (3) Add the challenge microbe to a sample
matrix in which it is likely to proliferate.
This guide will list key issues that must be addressed when designing ILS for Methods intended to
measure the microbial properties of fuels and fuel-associated waters.
1. Scope* 1.1.1 Microbial activity depends on the presence of avail-
able water. Consequently, the detection and quantification of
1.1 Microbiological test methods present challenges that are
microbial contamination in fuels and lubricants is made more
unique relative to chemical or physical parameters, because
complicated by the general absence of available water from
microbes proliferate, die off and continue to be metabolically
these fluids.
active in samples after those samples have been drawn from
their source. 1.1.2 Detectability depends on the physiological state and
taxonomic profile of microbes in samples. These two param-
eters are affected by various factors that are discussed in this
guide, and contribute to microbial data variability.
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This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
1.2 This guide addresses the unique considerations that
Subcommittee D02.14 on Stability, Cleanliness and Compatibility of Liquid Fuels.
must be accounted for in the design and execution of inter-
Current edition approved July 1, 2022. Published August 2022. Originally
approved in 2012. Last previous edition approved in 2017 as D7847 – 17. DOI:
laboratory studies intended to determine the precision of
10.1520/D7847-22.
microbiological test methods designed to quantify microbial
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Beckers, H. J., “Precision Testing of Standardized Microbiological Methods,”
contamination in fuels, lubricants and similar low water-
Journal of Testing and Evaluation, JTEVA, Vol. 14, No. 6, November 1986, pp.
318–320. content (water activity <0.8) fluids.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D7847 − 22
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1.3 This standard does not purport to address all of the 2.2 Energy Institute Standard:
safety concerns, if any, associated with its use. It is the
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