Tell me how handle failures during method validation
Please investigate into the matter thoroughly to identify the cause(s) of failure of method validation.
Generally, you may have to change the method parameters or steps such as solvents, dilutions / concentrations of solutions, pH of solution, extraction prodedure, interfering substances, chromatographic integration parameters & HPLC conditions, Resolution of chromatographic peaks, Flow rate, composition of mobile phase etc.
The type of change / modifications to be done will depend upon the cause(s) of failure of method validation parameters. (Accuracy, Precision, Specificity, Recovery, Stability of solutions, Linearity or range, Limit of detection, Limit of quantitation etc.)