ASTM D7235-05
(Guide)Standard Guide for Establishing a Linear Correlation Relationship Between Analyzer and Primary Test Method Results Using Relevant ASTM Standard Practices
Standard Guide for Establishing a Linear Correlation Relationship Between Analyzer and Primary Test Method Results Using Relevant ASTM Standard Practices
SCOPE
1.1 This guide covers a general methodology to develop and assess the linear relationship between results produced by a total analyzer system versus the results produced by the corresponding primary test method (PTM) that the analyzer system is intended to emulate, using the principles and approaches outlined in relevant ASTM standard practices and guides.
1.2 This guide describes how the statistical methodology of Practice D 6708 can be employed to assess agreement between the PTM and analyzer results, and, if necessary, develop linear correlation to further improve the agreement over the complete operating range of the analyzer. For instances where there is insufficient variation in property level to apply the Practice D 6708 multi-level methodology, users are referred to Practice D 3764 to perform a level specific bias evaluation. The correlation relationship information obtained in the application of this guide is applicable only to the material type and property range of the materials representative of those used to perform the assessment. Users are cautioned against extrapolation of the relationship beyond the material type and property range being studied.
1.3 This guide applies if the process stream analyzer system and the primary test method are based on the same measurement principle(s), or, if the process stream analyzer system uses a direct and well-understood measurement principle that is similar to the measurement principle of the primary test method. If the process stream analyzer system uses a different measurement technology from the primary test method, provided that the calibration protocol for the direct output of the analyzer does not require use of the PTM, this practice also applies.
1.4 This guide does not apply if the process stream analyzer system utilizes an indirect or mathematically modeled measurement principle such as chemometric or multivariate analysis techniques where results from PTM are required for the chemometric or multivariate model development. Users should refer to Practices E 1655 and D 6122 for detailed correlation and model validation procedures for these types of analyzer systems.Note 1
For example, this guide would apply for the comparison of benzene measurements from a mid-infrared process analyzer system based on Test Method D 6277 to those obtained using PTM Test Method D 3606, a gas chromatography based test method. For each sample, the mid-infrared spectrum is converted into a single analyzer result using methodology (Test Method D 6277) that is independent of the primary test method (Test Method D 3606). However, when the same analyzer uses a multivariate model to correlate the measured mid-infrared spectrum to Test Method D 3606 reference values using the methodology of Practice E 1655, this guide does not apply. In this case, the direct output of the analyzer is the spectrum, and the conversion of this multivariate output to an analyzer result require results from the primary test method.
1.5 This guide assumes that the analyzer sampling system is fit for use, and both analyzer and lab systems are in statistical control during the execution of the required tasks. Procedures for testing for proper function of the analyzer sampling system, and ascertaining whether the systems are in statistical control are beyond the scope of this guide.
1.6 Software program CompTM Version 1.0.21 (ADJD6708) performs the necessary computations recommended by this guide.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D7235 – 05
Standard Guide for
Establishing a Linear Correlation Relationship Between
Analyzer and Primary Test Method Results Using Relevant
1
ASTM Standard Practices
This standard is issued under the fixed designation D7235; 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
Operation of a process stream analyzer system typically involves four sequential activities: (1)
Analyzer Calibration—When an analyzer is initially installed, or after major maintenance has been
performed, diagnostic testing will typically be performed to demonstrate that the analyzer meets
manufacturer’sspecificationsandhistoricalperformancestandards.Thesediagnostictestsmayrequire
that the analyzer be adjusted so as to provide predetermined output levels for certain reference
materials. (2) Correlation to Primary Test Method—For process stream analyzer systems that are not
primary test methods (PTM), once the diagnostic testing is completed, process stream samples will
typically be analyzed using both the analyzer system and the corresponding primary test method. A
mathematical function will be derived that relates the analyzer output to the primary test method
(PTM).TheapplicationofthismathematicalfunctiontoananalyzeroutputproducesapredictedPTM
result. (3) Initial Validation—Once the relationship between the analyzer output and primary test
method results has been established, an initial validation is performed using an independent data set
to demonstrate that the predicted PTM results agree with those from the primary test method within
the tolerances established from the Correlation activities and with no observable systemic bias. (4)
Continual Validation—During normal operation of the process analyzer system, quality assurance
testing is conducted to demonstrate that the agreement between analyzer and primary test method
results during the Initial Validation is maintained. This document provides guidance for item (2)
above.
1. Scope correlation to further improve the agreement over the complete
operating range of the analyzer. For instances where there is
1.1 Thisguidecoversageneralmethodologytodevelopand
insufficient variation in property level to apply the Practice
assess the linear relationship between results produced by a
D6708 multi-level methodology, users are referred to Practice
total analyzer system versus the results produced by the
D3764 to perform a level specific bias evaluation. The corre-
corresponding primary test method (PTM) that the analyzer
lation relationship information obtained in the application of
system is intended to emulate, using the principles and ap-
this guide is applicable only to the material type and property
proaches outlined in relevant ASTM standard practices and
range of the materials representative of those used to perform
guides.
the assessment. Users are cautioned against extrapolation of
1.2 This guide describes how the statistical methodology of
the relationship beyond the material type and property range
Practice D6708 can be employed to assess agreement between
being studied.
the PTM and analyzer results, and, if necessary, develop linear
1.3 This guide applies if the process stream analyzer system
and the primary test method are based on the same measure-
1
This guide is under the jurisdiction of ASTM Committee D02 on Petroleum
ment principle(s), or, if the process stream analyzer system
Products and Lubricants and is the direct responsibility of Subcommittee D02.25 on
usesadirectandwell-understoodmeasurementprinciplethatis
Performance Assessment and Validation of Process Stream Analyzer Systems for
similar to the measurement principle of the primary test
Petroleum and Petroleum Products.
Current edition approved Dec. 1, 2005. Published February 2006. DOI: 10.1520/
method. If the process stream analyzer system uses a different
D7235-05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D7235 – 05
measurement technology from the primary test method, pro- Ignition Engine Fuels Using Mid Infrared Spectroscopy
vided that the calibration protocol for the direct output of the D6299 Practice for Applying Statistical Quality Assurance
analyzer does not require use of the PTM, this practice also and Control Charting Techniques to Evaluate Analytical
applies. Measurement System Performance
1.4 This guide does not apply if the process stream analyzer D6624 Practice for Determining a Flow-Proportioned Av-
system utilizes an indirect or mathe
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