ASTM D6259-23

Standard Practice for Determination of a Pooled Limit of Quantitation for a Test Method

SIGNIFICANCE AND USE
5.1 Background—In a single laboratory, the limit of quantitation, LOQ, equal to ten times the standard deviation obtained under repeatability conditions extrapolated to zero concentration (s0) based on samples with close to zero concentrations has been recommended.3 A test result at this LOQ has an uncertainty of ±30 % at the 99 % confidence level.  
5.1.1 This practice uses a regression technique to determine a similar limit for a test method (PLOQ) using statistically pooled repeatability standard deviations over multiple operators/laboratories/samples from ILS data. This PLOQ can be used by industry to assess the reliability of a test method, or, compare reliability of different test methods, for quantitative measurement at concentrations near zero. Similarly, quantitative test results obtained using the test method for levels at or below the PLOQ can be expected by industry to have an uncertainty of ±30 % or greater at the 95 % confidence level.  
5.1.2 The regression technique described in this practice can also be used to determine a limit of quantitation specific for a single laboratory (LLOQ). The limit thus quantified for one laboratory is defined by this standard as the laboratory limit of quantitation (LLOQ).  
5.1.3 It should be noted that since differences in repeatability testing capabilities between different laboratories can exist, therefore, LLOQ determined at a single laboratory can be different than the PLOQ determined for the test method.  
5.2 Values below the PLOQ are deemed by this practice to be too uncertain for meaningful use in commerce, or in regulatory activities.
SCOPE
1.1 This practice covers the use of standard regression techniques and data from an interlaboratory study to determine a lower quantitative limit for a test method. This determined lower limit represents the numerical limit at or above which the test results are considered to be quantitatively meaningful for commerce or regulatory activities by this practice. It is defined by this standard as the pooled limit of quantitation (PLOQ) for the test method.  
1.2 This practice is applicable to test methods that are capable of producing numerical test results close to zero. Examples are those test methods that determine quantitatively the concentration of analyte(s) near zero.  
1.3 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.

General Information

• Status: Published
• Publication Date: 30-Apr-2023
• ICS: 19.020 - Test conditions and procedures in general
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.94 - Coordinating Subcommittee on Quality Assurance and Statistics

Relations

• Refers: ASTM D6300-24 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Mar-2024
• Refers: ASTM D6300-23a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Dec-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D6300-19a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Dec-2019
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM D6300-16 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Apr-2016
• Refers: ASTM D6300-15 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Jun-2015
• Refers: ASTM D6300-14ae1 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Jun-2014
• Refers: ASTM D6300-14a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Jun-2014
• Refers: ASTM D6300-14 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-May-2014
• Refers: ASTM D6300-13a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Dec-2013
• Refers: ASTM E456-13a - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13ae3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13ae1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013

Overview

ASTM D6259-23: Standard Practice for Determination of a Pooled Limit of Quantitation for a Test Method is an internationally recognized standard developed by ASTM. This practice provides a statistically rigorous method for determining the pooled limit of quantitation (PLOQ) for test methods that yield quantitative results, especially at concentrations close to zero. The PLOQ is a vital metric for laboratories and industries that require reliable, low-level quantitative measurements-helping define the lower boundary at which reported results are considered meaningful for both commercial and regulatory purposes.

Key Topics

• Pooled Limit of Quantitation (PLOQ):
  • Represents the lowest concentration at which quantitative results from a test method can be deemed reliably meaningful.
  • Determined through standard regression techniques applied to data collected from multiple labs (ILS - interlaboratory studies).
• Laboratory Limit of Quantitation (LLOQ):
  • Similar determination but specific to a single laboratory's performance and repeatability.
• Repeatability and Uncertainty:
  • The standard outlines that test results at or below the PLOQ possess an uncertainty of ±30% at a 95% confidence level.
  • Results below the PLOQ are considered too uncertain for use in commerce or regulatory applications.
• Regression Technique:
  • Employs empirically derived regression functions (typically power functions) to estimate the PLOQ from pooled standard deviations across multiple laboratories and operators.
• Applicability:
  • Especially useful for test methods that measure concentrations or analytes near zero, such as in chemical analysis, environmental testing, and quality control of petroleum products.

Applications

ASTM D6259-23 finds practical value in a range of scientific and industrial settings:

• Quality Assurance in Testing Laboratories:
  • Provides a consistent, objective method for quantifying the lower detection limits of analytical procedures.
• Interlaboratory Studies and Method Validation:
  • Facilitates comparison of results across different laboratories through standardized determination of PLOQ.
• Regulatory Compliance:
  • Helps ensure that reported results meet necessary guidelines for uncertainty, supporting compliance with safety and environmental regulations.
• Selection and Validation of Analytical Methods:
  • Assists in method selection by allowing direct comparison of quantitative performance at low concentration levels.
• Reporting Low-Level Data:
  • Recommends that any results below the test method’s PLOQ be clearly reported, with the PLOQ indicated for transparency.

Related Standards

ASTM D6259-23 relies on and complements several other key standards:

• ASTM D6300 – Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• ASTM E456 – Terminology Relating to Quality and Statistics
• ASTM E691 – Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• ISO 4259 – Petroleum products-Determination and application of precision data in relation to methods of test

These related standards provide additional frameworks for conducting interlaboratory studies, ensuring measurement consistency, and understanding statistical concepts vital to quantitation limits.

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By adhering to ASTM D6259-23, organizations can enhance the reliability and comparability of low-level quantitative test results, bolstering confidence in data for both internal quality control and external regulatory submissions. The standard’s structured approach to determining the pooled limit of quantitation is essential for laboratories and industries focused on precise, low-concentration measurement.

Standards Content (Sample)

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: D6259 − 23 An American National Standard
Standard Practice for
Determination of a Pooled Limit of Quantitation for a Test
Method
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.
1. Scope* 3. Terminology
1.1 This practice covers the use of standard regression 3.1 Definitions:
techniques and data from an interlaboratory study to determine 3.1.1 repeatability conditions, n—conditions under which
a lower quantitative limit for a test method. This determined test results are obtained with the same test method in the same
lower limit represents the numerical limit at or above which the laboratory by the same operator with the same equipment in the
test results are considered to be quantitatively meaningful for shortest practical period of time using test units or test
commerce or regulatory activities by this practice. It is defined specimens taken at random from a single quantity of material
by this standard as the pooled limit of quantitation (PLOQ) for that is as nearly homogeneous as possible.
the test method.
NOTE 1—By in the shortest practical period of time is meant that the
test results, at least for one material, are obtained in a time period not less
1.2 This practice is applicable to test methods that are
than in normal testing and not so long as to permit significant change in
capable of producing numerical test results close to zero.
test material, equipment, or environment. See Terminology E456.
Examples are those test methods that determine quantitatively
3.2 Definitions of Terms Specific to This Standard:
the concentration of analyte(s) near zero.
3.2.1 pooled limit of quantitation (PLOQ), n—level of
1.3 This international standard was developed in accor-
property or concentration for a test method at which the ratio:
dance with internationally recognized principles on standard-
[10× pooled repeatability standard deviation of results for a
ization established in the Decision on Principles for the
concentration level/concentration level] = 1.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.2.1.1 Discussion—Quantitative test results obtained using
Barriers to Trade (TBT) Committee.
a test method at or below its PLOQ is expected to have an
uncertainty of 630 % or greater at the 95 % confidence level.
2. Referenced Documents
3.2.2 pooled repeatability standard deviation, n—the statis-
tically pooled standard deviation for results obtained under
2.1 ASTM Standards:
repeatability conditions over multiple operators/laboratories
D6300 Practice for Determination of Precision and Bias
for a sample that is obtained in accordance with Practice
Data for Use in Test Methods for Petroleum Products,
D6300 or other equivalent Interlaboratory Study (ILS) analysis
Liquid Fuels, and Lubricants
(for example, Practice E691, ISO 4259).
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to
3.2.3 laboratory limit of quantitation (LLOQ), n—level of
Determine the Precision of a Test Method
property or concentration for a test method at which the ratio:
[10× repeatability standard deviation of results for a concen-
tration level determined in a single laboratory/concentration
This practice is under the jurisdiction of Committee D02 on Petroleum
level] = 1.
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
mittee D02.94 on Coordinating Subcommittee on Quality Assurance and Statistics.
3.2.3.1 Discussion—Quantitative test results obtained by
Current edition approved May 1, 2023. Published May 2023. Originally
this single laboratory at or below its LLOQ is expected to have
approved in 1998. Last previous edition approved in 2019 as D6259 – 15 (2019).
DOI: 10.1520/D6259-23.
an uncertainty of 630 % or greater at the 95 % confidence
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
level.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3.3 Acronyms:
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 3.3.1 ILS, n—interlaboratory study.
*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
D6259 − 23
3.3.2 LLOQ, n—laboratory limit of quanitation. to estimate the PLOQ (see Note 2). The ILS can include more
than seven test levels. However, for use of regression for
3.3.3 PLOQ, n—pooled limit of quantitation.
PLOQ only, use results from samples meeting the following
4. Summary of Practice requirements:
6.2.1.1 At least four shall have Y values (see Section 4,
4.1 Statistically pooled repeatability standard deviations
Summary of Practice) greater than 0.5,
from multiple laboratories for at least seven samples meeting
6.2.1.2 At least one shall have a Y value less than 0.5,
the requirements in Section 6 are obtained.
6.2.1.3 At least one shall have a Y value between 0.5 and 1,
4.2 An empirical power function is fitted to the plot Y versus
6.2.1.4 At least two of the seven samples shall have a Y
X where:
value greater than 1.2, and
6.2.1.5 No sample should exceed 4 times the estimated
Y = [10× pooled repeatability standard deviation/mean] for
PLOQ.
each sample, and
6.2.1.6 See Table 1 for an example.
X = [mean] of each sample.
NOTE 2—Mean and standard deviation data from experienced
4.3 The value of X at which the evaluated Y = 1 is
laboratories, archived research reports, and known limitations of the test
determined using the function determined in 4.2. This value of
method or equipment can give a preliminary notion of the PLOQ.
X is defined as the PLOQ for the method.
6.2.2 Select Sample Materials—Use sample materials that
are typical of those to which the test method is applied. In
5. Significance and Use
special cases, the method of standard additions (spiking) can be
5.1 Background—In a single laboratory, the limit of
necessary to achieve the selected test levels. Synthetic blends
quantitation, LOQ, eq
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6259 − 15 (Reapproved 2019) D6259 − 23 An American National Standard
Standard Practice for
Determination of a Pooled Limit of Quantitation for a Test
Method
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.
1. Scope Scope*
1.1 This practice covers the use of standard regression techniques and data from an interlaboratory study to determine a lower
quantitative limit for a test method. This determined lower limit represents the numerical limit at or above which the test results
are considered to be quantitatively meaningful for commerce or regulatory activities by this practice. It is defined by this standard
as the pooled limit of quantitation (PLOQ) for the test method.
1.2 This practice is applicable to test methods that are capable of producing numerical test results close to zero. Examples are those
test methods that determine quantitatively the concentration of analyte(s) near zero.
1.3 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.
2. Referenced Documents
2.1 ASTM Standards:
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and
Lubricants
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions:
3.1.1 repeatability conditions, n—conditions under which test results are obtained with the same test method in the same
laboratory by the same operator with the same equipment in the shortest practical period of time using test units or test specimens
taken at random from a single quantity of material that is as nearly homogeneous as possible.
NOTE 1—By in the shortest practical period of time is meant that the test results, at least for one material, are obtained in a time period not less than in
normal testing and not so long as to permit significant change in test material, equipment, or environment. See Terminology E456.
3.2 Definitions of Terms Specific to This Standard:
This practice is under the jurisdiction of Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee D02.94
on Coordinating Subcommittee on Quality Assurance and Statistics.
Current edition approved May 1, 2019May 1, 2023. Published June 2019May 2023. Originally approved in 1998. Last previous edition approved in 20152019 as
D6259 – 15.D6259 – 15 (2019). DOI: 10.1520/D6259-15R19.10.1520/D6259-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*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
D6259 − 23
3.2.1 pooled limit of quantitation (PLOQ), n—level of property or concentration for a test method at which the ratio: [10× pooled
repeatability standard deviation of results for a concentration level/concentration level] = 1.
3.2.1.1 Discussion—
Quantitative test results obtained using a test method at or below its PLOQ is expected to have an uncertainty of 630 % or greater
at the 95 % confidence level.
3.2.2 pooled repeatability standard deviation, n—the statistically pooled standard deviation for results obtained under repeatability
conditions over multiple operators/laboratories for a sample that is obtained in accordance with Practice D6300 or other equivalent
Interlaboratory Study (ILS) analysis (for example, Practice E691, ISO 4259).
3.2.3 laboratory limit of quantitation (LLOQ), n—level of property or concentration for a test method at which the ratio: [10×
repeatability standard deviation of results for a concentration level determined in a single laboratory/concentration level] = 1.
3.2.3.1 Discussion—
Quantitative test results obtained by this single laboratory at or below its LLOQ is expected to have an uncertainty of 630 % or
greater at the 95 % confidence level.
3.3 Acronyms:
3.3.1 ILS, n—interlaboratory study.
3.3.2 LLOQ, n—laboratory limit of quanitation.
3.3.3 PLOQ, n—pooled limit of quantitation.
4. Summary of Practice
4.1 Statistically pooled repeatability standard deviations from multiple laboratories for at least seven samples meeting the
requirements in Section 6 are obtained.
4.2 An empirical power function is fitted to the plot Y versus X where:
Y = [10× pooled repeatability standard deviation/mean] for each sample, and
X = [mean] of each sample.
4.3 The value of X at which the evaluated Y = 1 is determined using the function determined in 4.2. This value of X is defined
as the PLOQ for the method.
5. Significance and Use
5.1 Background—In a single laboratory, the limit of quantitation, LOQ, equal to ten times the standard deviation obtained under
repeatability conditions extrapolated to zero concentration (s ) based on samples with close to zero concentrations has been
recommended. A test result at this LOQ has an uncertainty of 630 % at the 99 % confidence level.
5.1.1 This practice uses a regression technique to determine a similar limit for a test method (PLOQ) using statistically pooled
repeatability standard deviations over multiple operators/laboratories/samples from ILS data. This PLOQ can be used by industry
to assess the reliability of a test method, or, compare reliability of different test methods, for quantitative measurement at
concentrations near zero. Similarly, quantitative test results obtained using the test method for levels at or below the PLOQ can
be expected by industry to have an uncertainty of 630 % or greater at the 95 % confidence level.
5.1.2 The regression technique described in this practice can also be used to
...