ASTM D7235-14

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Designation: D7235 − 10 D7235 − 14
Standard Guide for
Establishing a Linear Correlation Relationship Between
Analyzer and Primary Test Method Results Using Relevant
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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’s specifications and historical performance standards. These diagnostic tests may require
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 where the
application objective is to provide prediction of results from a Primary Test method, 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). The application of this mathematical
function to an analyzer output produces a predicted PTM 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 statistically 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 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 D6708 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 D6708
multi-level methodology, users are referred to Practice D3764 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
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This guide is under the jurisdiction of ASTM Committee D02 on Petroleum Products Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.25 on Performance Assessment and Validation of Process Stream Analyzer Systems.
Current edition approved July 1, 2010Dec. 1, 2014. Published October 2010January 2015. Originally approved in 2005. Last previous edition approved in 20052010 as
D7235–05.D7235 – 10. DOI: 10.1520/D7235-10.10.1520/D7235-14.
*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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