Method validation is the process of demonstrating that an analytical method is suitable for its intended purpose. For standard methods, the laboratory performs method verification to confirm that it can achieve the expected performance. For non-standard or developed methods, full validation is required.
Key performance characteristics include accuracy, which measures closeness to the true value and is assessed using reference materials or recovery studies. Precision encompasses repeatability (same conditions, short time), intermediate precision (same lab, different days or analysts), and reproducibility (different laboratories). Precision is expressed as relative standard deviation.
Trueness is the closeness of agreement between the average of replicate measurements and the accepted reference value. The measurement uncertainty combines all sources of error into a single interval expected to contain the true value.
Specificity demonstrates that the method measures the analyte without interference from matrix components, degradation products, or related substances. The detection limit is the smallest quantity that can be detected but not necessarily quantified. The quantification limit is the smallest quantity that can be quantified with acceptable precision and accuracy.
Linearity shows that the response is proportional to the analyte concentration over the working range, evaluated by the correlation coefficient and residual analysis. The working range spans from the quantification limit to the highest concentration with acceptable performance. Robustness tests assess the method’s resistance to deliberate variations in parameters such as pH, temperature, flow rate, and column age.
Method validation follows guidelines from ICH Q2(R1) for pharmaceutical methods, AOAC for food methods, and ISO 17025 for general laboratory methods. The validation protocol specifies the performance characteristics to be evaluated, acceptance criteria, and statistical procedures. A validation report documents the results and conclusions.
