method validation for non-routine methods

Method validation for non-routine methods

Angelique Botha

Test and Measurement 2019 Conference

Misty Hills Conference Hotel

17 September 2019

Overview

✓ Concept of method validation

✓ Method validation parameters

✓ Non-routine methods

Concept of method validation

Method

Fit for purpose

Customer requirements

Specific laboratory

Concept of method validation

Method validation

Overall method performance

Specific influence quantities

Normal use

Uncertainty of Measurement

Concept of method validation

Method validation

data

Method development (optimisation)

Interlaboratory studies

In-house validation

Precision and bias

Method validation parameters

✓ Principle of operation

✓ Precision

✓ Bias

✓ Linearity

✓ Limit of detection (LOD)

✓ Limit of quantification (LOQ)

✓ Working range

✓ Selectivity

✓ Robustness/Ruggedness

✓ Uncertainty of measurement

EURACHEM/CITAC Guide “Fitness for Purpose of Analytical Methods”,

Second edition, www.eurachem.org

Precision study

Precision

Repeatability

Reproducibility

Intermediate precision

Bias (“Trueness”) study

Bias

Certified reference materials (CRMs)

Spiking studies

Reference method

Eliminate

Linearity

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Concentration mg/L

Cadmium in pineapples

Limit of detection

blankblankLOD syy += 3

LODLOD xy →

y

xLOD say += 3

Limit of quantification

For linear regression:

x

yLOQ say += 10

Working range

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Concentration mg/L

Cadmium in pineapples

LOD

LOQ

Working range

✓ Perform tests to determine the effect of one or more parameter changes on the results

✓ If the effect is significant a more detailed study is carried out to measure the size of the effect

✓ Significant effect: the precision deteriorated compared to the precision of the ruggedness test (ANOVA, F-test)

Robustness (ruggedness)

✓ The degree to which a method responds uniquely to the required analyte

✓ Typical studies investigate the effects of likely interferents by adding the potential interferent to both blank and fortified samples and observing the response

✓ Normally used to demonstrate insignificant effects

✓ Can use the data to estimate the uncertainty associated with potential interferences

Selectivity/specificity

Method validation for non-routine methods

Non-routine

methods

Standard method

Performance data

Bias

Duplicate analysis

Standard method

Weigh 0,5 g aliquot of soil

sample

Add 8 mL HNO3, 5 mL

HCl, 3 mL HF

Leave overnight

First microwave

digestion step

Add 1 mL HF, 15 mL 5%

H3BO3

Second microwave

digestion step

Add internal standard

Matrix matchFill to the

mark

DiluteICP-MS analysis

Standard method

Weigh 0,5 g aliquot of soil

sample

Add 8 mL HNO3, 5 mL

HCl, 3 mL HF

Leave overnight

First microwave

digestion step

Add 1 mL HF, 15 mL 5%

H3BO3

Second microwave

digestion step

Add internal standard

Matrix matchFill to the

mark

DiluteICP-MS analysis

Standard method

Weigh 0,5 g aliquot of soil

sample

Add 8 mL HNO3, 5 mL

HCl, 3 mL HF

Leave overnight

First microwave

digestion step

Add 1 mL HF, 15 mL 5%

H3BO3

Second microwave

digestion step

Add internal standard

Matrix matchFill to the

mark

DiluteICP-MS analysis

Standard method

Weigh 0,5 g aliquot of

rock sample

Add 8 mL HNO3, 5 mL

HCl, 3 mL HF

Leave overnight

First microwave

digestion step

Add 1 mL HF, 15 mL 5%

H3BO3

Second microwave

digestion step

Add internal standard

Matrix matchFill to the

mark

DiluteICP-MS analysis

Standard method

Weigh 0,5 g aliquot of

rock sample

Add 10 mL HNO3, 6 mL

HCl, 5 mL HF

Leave overnight

First microwave

digestion step

Add 1 mL HF, 15 mL 5%

H3BO3

Second microwave

digestion step

Add internal standard

Matrix match Fill to the mark

DiluteICP-MS analysis