1. Good Laboratory Practice: Quality Assurance of Analytical Measurements
Section Four
Good Laboratory Practice:
Quality Assurance of Analytical Measurements

2. What is Good Laboratory Practice (GLP)?
The goal of GLP is to certify that every step of the analysis is valid.
Standard Operating Procedures (SOP)
Quality Assurance Unit (QAU)

3. Validation of Analytical Methods
Defintion
Example
Technique
Scientific principle gives compositional information
Spectrophotometry
Method
Distinct adaptation of technique selected measurement purpose
Pararosaniline method to determine SO2
Procedure
Written directions to use a method
ASTM D2914
Sulfur Dioxide
Protocol
Set of definitive directions that must be followed, without exception
EPA Reference Method Determine SO2 Atmosphere

4. Fig. 4.1. General process for evaluation/validation of methodology.
Validation involves determining:
selectivity
linearity
accuracy
precision
sensitivity
range
limit of detection
limit of quantitation
ruggedness/robustness
Standard reference materials (SRMs) best for determining accuracy.
Fig General process for evaluation/validation of methodology.
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)

5. Fig. 4.2. Response factor plot for Figure 3.8. (p. 104)
RF = (signal – y intercept)/(concentration).
A zero slope indicates linear response over the concentration range selected.
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)
Fig Response factor plot for Figure 3.8. (p. 104)

6. Fig. 4.3. Dependence of relative standard deviation on concentration.
The precision becomes poorer at low concentrations.
(Also sometimes at high concentrations, as in spectrophotometric measurements –see spectrometric error, Fig )
Fig Dependence of relative standard deviation on concentration.
©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley)

7. Fig. 4.4. Representative z-value distributions for
Z = (Xi-X)/s = (mean conc. of lab – accepted conc.)/(S.D. accepted conc.)
A z-value of 2 means a lab is two S.D. away from the accepted value (95% chance of systematic error).
Fig Representative z-value distributions for
proficiency tests with a series of laboratories.
©Gary Christian, Analytical Chemistry, th Ed. (Wiley)