ASTM D6122-06
(Practice)Standard Practice for Validation of the Performance of Multivariate Process Infrared Spectrophotometers
Standard Practice for Validation of the Performance of Multivariate Process Infrared Spectrophotometers
SCOPE
1.1 This practice covers requirements for the validation of measurements made by online, process near- or mid-infrared analyzers, or both, used in the calculation of physical, chemical, or quality parameters (that is, properties) of liquid petroleum products. The properties are calculated from spectroscopic data using multivariate modeling methods. The requirements include verification of adequate instrument performance, verification of the applicability of the calibration model to the spectrum of the sample under test, and verification of equivalence between the result calculated from the infrared measurements and the result produced by the primary test method used for the development of the calibration model. When there is adequate variation in property level, the statistical methodology of Practice D 6708 is used to provide general validation of this equivalence over the complete operating range of the analyzer. For cases where there is inadequate property variation, methodology for level specific validation is used.
1.2 Performance Validation is conducted by calculating the precision and bias of the differences between results from the analyzer system (or subsystem) produced by application of the multivariate model, (such results are herein referred to as Predicted Primary Test Method Results (PPTMRs)), versus the Primary Test Method Results (PTMRs) for the same sample set. Results used in the calculation are for samples that are not used in the development of the multivariate model. The calculated precision and bias are statistically compared to user-specified requirements for the analyzer system application.
1.2.1 For analyzers used in product release or product quality certification applications, the precision and bias requirement for the degree of agreement are typically based on the site or published precision of the Primary Test Method.Note 1
In most applications of this type, the PTM is the specification-cited test method.
1.2.2 This practice does not does not describe procedures for establishing precision and bias requirements for analyzer system applications. Such requirements must be based on the criticality of the results to the intended business application and on contractual and regulatory requirements. The user must establish precision and bias requirements prior to initiating the validation procedures described herein.
1.3 This practice does not cover procedures for establishing the calibration model (correlation) used by the analyzer. Calibration procedures are covered in Practices E 1655 and references therein.
1.4 This practice is intended as a review for experienced persons. For novices, this practice will serve as an overview of techniques used to verify instrument performance, to verify model applicability to the spectrum of the sample under test, and to verify equivalence between the parameters calculated from the infrared measurement and the results of the primary test method measurement.
1.5 This practice teaches and recommends appropriate statistical tools, outlier detection methods, for determining whether the spectrum of the sample under test is a member of the population of spectra used for the analyzer calibration. The statistical tools are used to determine if the infrared measurement results in a valid property or parameter estimate.
1.6 The outlier detection methods do not define criteria to determine whether the sample or the instrument is the cause of an outlier measurement. Thus, the operator who is measuring samples on a routine basis will find criteria to determine that a spectral measurement lies outside the calibration, but will not have specific information on the cause of the outlier. This practice does suggest methods by which instrument performance tests can be used to indicate if the outlier methods are responding to changes in the instrument response.
1.7 This practice is not intended as a quantitative performance standard for the comparison of analyze...
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An American National Standard
Designation:D6122–06
Standard Practice for
Validation of the Performance of Multivariate Process
1
Infrared Spectrophotometers
This standard is issued under the fixed designation D6122; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) 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 is performed to demonstrate that the analyzer meets the
manufacturer’sspecificationsandhistoricalperformancestandards.Thesediagnostictestsmayrequire
that the analyzer be adjusted so as to provide predetermined output levels for certain reference
materials. (2)Correlation—Once the diagnostic testing is completed, process stream samples are
analyzed using both the analyzer system and the corresponding primary test method (PTM). A
mathematical function is derived that relates the analyzer output to the primary test method (PTM).
The application of this mathematical function to an analyzer output produces a predicted primary test
method result (PPTMR). (3)Probationary Validation—Once the relationship between the analyzer
outputandPTMRshasbeenestablished,aprobationaryvalidationisperformedusinganindependent
but limited set of materials that were not part of the correlation activity. This probationary validation
is intended to demonstrate that the PPTMRs agree with the PTMRs to within user-specified
requirements for the analyzer system application. (4)General and Continual Validation—After an
adequate number of PPTMRs and PTMRs have been accrued on materials that were not part of the
correlation activity, a comprehensive statistical assessment is performed to demonstrate that the
PPTMRs agree with the PTMRs to within user-specified requirements. Subsequent to a successful
general validation, quality assurance control chart monitoring of the differences between PPTMR and
PTMR is conducted during normal operation of the process analyzer system to demonstrate that the
agreement between the PPTMRs and the PTMRs established during the General Validation is
maintained. This practice deals with the third and fourth of these activities.
1. Scope of equivalence between the result calculated from the infrared
measurements and the result produced by the primary test
1.1 This practice covers requirements for the validation of
method used for the development of the calibration model.
measurements made by online, process near- or mid-infrared
When there is adequate variation in property level, the statis-
analyzers, or both, used in the calculation of physical, chemi-
tical methodology of Practice D6708 is used to provide
cal, or quality parameters (that is, properties) of liquid petro-
general validation of this equivalence over the complete
leum products. The properties are calculated from spectro-
operating range of the analyzer. For cases where there is
scopic data using multivariate modeling methods. The
inadequate property variation, methodology for level specific
requirements include verification of adequate instrument per-
validation is used.
formance, verification of the applicability of the calibration
1.2 Performance Validation is conducted by calculating the
modeltothespectrumofthesampleundertest,andverification
precision and bias of the differences between results from the
analyzer system (or subsystem) produced by application of the
1
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum multivariate model, (such results are herein referred to as
ProductsandLubricantsandisthedirectresponsibilityofSubcommitteeD02.25on
PredictedPrimaryTestMethodResults(PPTMRs)),versusthe
Performance Assessment and Validation of Process Stream Analyzer Systems for
Primary Test Method Results (PTMRs) for the same sample
Petroleum and Petroleum Products.
set. Results used in the calculation are for samples that are not
Current edition approved July 1, 2006. Published August 2006. Originally
approved in 1997. Last previous edition approved in 2001 as D6122–01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6122–06
used in the development of the multivariate model. The 2. Referenced Documents
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calculated precision and bias are statistically compared to
2.1 ASTM Standards:
user-specified requirements for the analyzer system applica-
D1265 Practice for Sampling Liquefied Petroleum (LP)
tion.
Gases, Man
...
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