Submitted by: sdemir   Date: 2021-01-14 11:19
The Fitness for Purpose of Analytical Methods
A Laboratory Guide to Method Validation and Related Topics

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Contents
Foreword to the second edition ................................................................................................. 1
Foreword to the first edition ..................................................................................................... 2
Abbreviations and symbols ........................................................................................................ 3
1 Introduction ........................................................................................................................ 5
1.1 Rationale and scope for this Guide ...................................................................................... 5
1.2 Notes on the use of this Guide .............................................................................................. 5
1.2.1 Terminology ...................................................................................................................................... 5
1.2.2 Quick References .............................................................................................................................. 6
2 What is method validation? ............................................................................................... 7
2.1 Definitions .............................................................................................................................. 7
2.2 What is the difference between validation and verification? ............................................ 7
3 Why is method validation necessary? ................................................................................ 9
3.1 Importance of analytical measurement ............................................................................... 9
3.2 The professional duty of the analytical chemist .................................................................. 9
3.3 Method development ............................................................................................................. 9
4 When should methods be validated or verified? ............................................................. 11
4.1 Method validation................................................................................................................ 11
4.2 Method verification ............................................................................................................. 11
5 How should methods be validated? ................................................................................. 13
5.1 Who carries out method validation? .................................................................................. 13
5.1.1 Approaches to method validation .....................................................................................................13
5.1.2 Interlaboratory approach ..................................................................................................................13
5.1.3 Single-laboratory approach ..............................................................................................................13
5.2 Extent of validation studies ................................................................................................ 13
5.3 Validation plan and report ................................................................................................. 14
5.4 Validation tools .................................................................................................................... 15
5.4.1 Blanks...............................................................................................................................................15
5.4.2 Routine test samples .........................................................................................................................15
5.4.3 Spiked materials/solutions ................................................................................................................15
5.4.4 Incurred materials .............................................................................................................................15
5.4.5 Measurement standards ....................................................................................................................15
5.4.6 Statistics ...........................................................................................................................................16
5.5 Validation requirements ..................................................................................................... 16
5.6 Method validation process .................................................................................................. 16
6 Method performance characteristics ............................................................................... 19
6.1 Selectivity ............................................................................................................................. 19
6.1.1 Terms and definitions .......................................................................................................................19
6.1.2 Effects of interferences .....................................................................................................................19
6.1.3 Assessment of selectivity .................................................................................................................19

The Fitness for Purpose of Analytical Methods Eurachem Guide
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6.2 Limit of detection and limit of quantification ................................................................... 20
6.2.1 Terms and definitions .......................................................................................................................20
6.2.2 Determination of the standard deviation at low levels .....................................................................21
6.2.3 Estimating LOD ...............................................................................................................................24
6.2.4 Estimating LOQ ...............................................................................................................................24
6.2.5 Alternative procedures .....................................................................................................................25
6.2.6 Capability of detection for qualitative analysis ................................................................................25
6.3 Working range ..................................................................................................................... 27
6.3.1 Definition .........................................................................................................................................27
6.3.2 Considerations for the validation study ............................................................................................27
6.3.3 Method and instrument working range.............................................................................................27
6.3.4 Assessing instrument working range ................................................................................................27
6.3.5 Assessing method working range .....................................................................................................28
6.4 Analytical sensitivity ........................................................................................................... 30
6.4.1 Definition .........................................................................................................................................30
6.4.2 Applications .....................................................................................................................................30
6.5 Trueness ............................................................................................................................... 30
6.5.1 Terminology to describe measurement quality ................................................................................30
6.5.2 Determination of bias .......................................................................................................................31
6.5.3 Interpreting bias measurements ........................................................................................................34
6.6 Precision ............................................................................................................................... 35
6.6.1 Replication .......................................................................................................................................35
6.6.2 Precision conditions .........................................................................................................................35
6.6.3 Precision limits .................................................................................................................................36
6.6.4 Simultaneous determination of repeatability and intermediate precision .........................................36
6.7 Measurement uncertainty ................................................................................................... 38
6.8 Ruggedness ........................................................................................................................... 38
6.8.1 Definition .........................................................................................................................................38
6.8.2 Ruggedness test ................................................................................................................................38
7 Using validated methods .................................................................................................. 41
8 Using validation data to design quality control .............................................................. 43
8.1 Introduction ......................................................................................................................... 43
8.2 Internal quality control ....................................................................................................... 43
8.3 External quality control ...................................................................................................... 44
9 Documentation of validated methods .............................................................................. 45
9.1 From draft to final version ................................................................................................. 45
9.2 Recommendations ............................................................................................................... 45
9.2.1 Checking the instructions .................................................................................................................45
9.2.2 Recommendations in standards ........................................................................................................45
9.2.3 Document control .............................................................................................................................45
10 Implications of validation data for calculating and reporting results........................ 47
Annex A – Method documentation protocol .......................................................................... 49
Annex B – Statistical basis of limit of detection calculations ................................................ 53
Annex C – Analysis of variance (ANOVA) ............................................................................ 54
Annex D – Notes on qualitative analysis ................................................................................ 56
Bibliography ............................................................................................................................ 59

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