Good Laboratory Practices GLP An Introduction GLP Objectives • To (quantitatively) describe instrument performance so that analytical measurements of unknowns can result in a quantitative result. • For example: Calibration of a spectrofluorometer with quinine, followed by the analysis of unknown concentrations of quinine in tonic water. Analytical Method Considerations COST SPEED NEEDS • COST: Training, equipment... • SPEED: When is it required... • NEEDS: E.g., required detection limit... • Overall: An equal balance among the three. Basic Terms Chapter 1 Page 11, Table 1-3 (Skoog Holler Nieman) • Precision (Reproducibility): Absolute or relative standard deviation, coefficient of variation, variance • Bias: Absolute or relative systematic error • Sensitivity: Calibration or analytical... • Response Factor: Response as a function of analyte concentration • Limit of Quantitation (LOQ): A numerical value usually directly related to LOD (>) • Detection Limit (LOD or MDL): Different methods (statistical) to establish LOD • Not Detected: Signal not discernible from noise using the given analytical system • Concentration Range: From LOQ to LOL • Selectivity: Coefficient of selectivity (%) t-Test - Comparison of Means • Mean of TEST METHOD #1 (sample) X 1 • Mean of TEST METHOD #2 (sample) X 2 • Are the means equal? The t-test we use is dependent on whether the variances of the two test methods are the same or different. Again, assume Gaussian Distributions. One-tailed t-test for equal variances, and two-tailed for unequal variances. The two-tailed presents more relaxed constraints on establishing equivalence.