method validation for non-routine methods
TRANSCRIPT
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
