ASTM D6259-98(2010)
(Practice)Standard Practice for Determination of a Pooled Limit of Quantitation
Standard Practice for Determination of a Pooled Limit of Quantitation
SIGNIFICANCE AND USE
In a single laboratory, the limit of quantitation, LOQ, equal to ten standard deviations has been recommended.4 A test result at this LOQ has an uncertainty of ±30 % at the 99 % confidence level. Similarly here, as a general estimate, the PLOQ, equal to ten repeatability standard deviations is recommended. A test result at this PLOQ has an uncertainty of ±30 % at the 99 % confidence level.
Values below the PLOQ are deemed to be too uncertain for meaningful use in commerce, or in regulatory activities.
Many test methods never find application outside their PLOQ. However, in the quest for ever more sensitive procedures, it can become difficult to distinguish an analytical response from background noise with the technology at hand. Test methods defective in design or poorly executed may also function outside their PLOQ.
SCOPE
1.1 This practice covers the determination of a lower quantitative limit for a test method for an analyte. The determined lower limit is hereinafter referred to as the pooled limit of quantitation.
1.2 Applicable test methods will produce test results greater than zero. Examples are those test methods that measure sample composition.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6259 − 98(Reapproved 2010) An American National Standard
Standard Practice for
Determination of a Pooled Limit of Quantitation
This standard is issued under the fixed designation D6259; 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.
for a particular step in the measurement process the same combination of
1. Scope
operator and equipment is used for every test result. Thus, one operator
1.1 This practice covers the determination of a lower
may prepare the test specimens, a second measure the dimensions, and a
quantitative limit for a test method for an analyte. The third measure the mass in a test method for measuring density.
NOTE 2—By in the shortest practical period of time is meant that the
determined lower limit is hereinafter referred to as the pooled
test results, at least for one material, are obtained in a time period not less
limit of quantitation.
than in normal testing and not so long as to permit significant change in
1.2 Applicable test methods will produce test results greater test material, equipment, or environment. See Terminology E456.
than zero. Examples are those test methods that measure
3.2 Acronyms:
sample composition.
3.2.1 PLOQ, n—pooled limit of quantitation.
2. Referenced Documents
4. Summary of Practice
2.1 ASTM Standards:
4.1 Determine the standard deviation of a test result, under
E456 Terminology Relating to Quality and Statistics
repeatability conditions, at progressively higher levels of the
E691 Practice for Conducting an Interlaboratory Study to
analyte until the ratio of measured level to standard deviation
Determine the Precision of a Test Method
becomes greater than ten and remains so.
2.2 ASTM Adjuncts:
D2PP, Determination of Precision and Bias Data for Use in
5. Significance and Use
Test Methods for Petroleum Products
5.1 In a single laboratory, the limit of quantitation, LOQ,
equaltotenstandarddeviationshasbeenrecommended. Atest
3. Terminology
result at this LOQ has an uncertainty of 630 % at the 99 %
3.1 Definitions:
confidence level. Similarly here, as a general estimate, the
3.1.1 pooled limit of quantitation, n—level of property or
PLOQ, equal to ten repeatability standard deviations is recom-
concentration of analyte above which quantitative test results
mended. A test result at this PLOQ has an uncertainty of
can be obtained with a specified degree of confidence. See
630 % at the 99 % confidence level.
3.2.1 for acronym.
5.2 Values below the PLOQ are deemed to be too uncertain
3.1.2 repeatability conditions, n—conditions under which
for meaningful use in commerce, or in regulatory activities.
test results are obtained with the same test method in the same
5.3 Many test methods never find application outside their
laboratorybythesameoperatorwiththesameequipmentinthe
PLOQ. However, in the quest for ever more sensitive
shortest practical period of time using test units or test
procedures, it can become difficult to distinguish an analytical
specimens taken at random from a single quantity of material
response from background noise with the technology at hand.
that is as nearly homogeneous as possible (see 10.3 of Practice
Test methods defective in design or poorly executed may also
E691.)
function outside their PLOQ.
NOTE 1—The same operator, same equipment requirement means that
6. Procedure
1 6.1 Makethepreparationsoutlinedin6.2,thencarryoutone
ThispracticeisunderthejurisdictionofCommitteeD02onPetroleumProducts
and Lubricantsand is the direct responsibility of Subcommittee D02.94 on Coordi- of the procedures described in 6.3.
nating Subcommittee on Quality Assurance and Statistics.
6.2 Preparations:
Current edition approved July 1, 2010. Published July 2010. Originally approved
in 1998. Last previous edition approved in 2004 as D6259–98(2004). DOI: 6.2.1 Select Test Levels—Decide the objective of the test
10.1520/D6259-98R10.
method, the range of typical samples it is expected to cover.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Keith, L. H., et al, “Principles of Environmental Analysis,” Analytical
Withdrawn and no longer available from ASTM International. Chemistry, American Chemical Society, Vol 55, 1983, p. 227.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6259 − 98 (2010)
TABLE 2 Abbreviated Example—One Laboratory
Name a set of test levels covering this range and spaced to
bracket the PLOQ. In some cases, the PLOQ will be well Run\Sample A Blank A-Blank B Blank B-Blank
below the useful range. Then, it is only necessary to determine 1 800 10 790 1050 20 1030
2 900 5 895 1250 20 1230
a less than value.
3 900 10 890 1250 5 1245
4 800 0 800 1300 0 1300
NOTE 3—Mean and standard deviation data from experienced labora-
5 750 0 750 1200 5 1195
tories, archived research reports, and known limitations of the test method
6 950 20 930 1100 10 1090
or equipment can give a preliminary notion of the PLOQ.An LOQ can be
7 1000 5 995 1150 5 1145
estimated in a single laboratory.
Mean 864.3 1176.4
Standard
6.2.2 Select Sample Materials—Normally, use sample ma-
87.29 94.06
Deviation
terials that are typical of those to which the test method is
Ratio Mean/ - -
A
applied. In special cases, the method of standard additions Standard 9.9 12.5
Deviation
(spiking) can be necessary
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.