The validity of aspecific method proposed to a particular analysis should be demonstrated inlaboratory experiments using samples or standards that are similar to unknownsamples analyzed routinely. The preparation and execution should follow avalidation protocol which is pre-documented, preferably written in a step-by-stepinstruction format.
Possible steps for a complete method validation are listedbelow. Develop a validation protocol, an operating procedure or a validation master plan for the validation. For a specific validation project define owners and responsibilities Develop a validation project plan. Define the application, purpose and scope of the method. Define the performance parameters and acceptance criteria. Define validation experiments. Verify relevant performance characteristics of equipment.
Qualify materials, e.g. standards and reagents for purity, accurate amounts and sufficient stability. Perform pre-validation experiments. Adjust method parameters or/and acceptance criteria if necessary. Perform full internal (and external) validation experiments.
Develop SOPs for executing the method in the routine. Define criteria for revalidation. Define type and frequency of system suitability tests and/or analytical quality control (AQC) checks for the routine. Document validation experiments and results in the validation report.This proposedprocedure assumes that the instrument has been selected and the method has beendeveloped. Instrument should meets criteria such as ease of use; ability to beautomated and to be controlled by computer systems; costs per analysis; samplethroughput; turnaround time; and environmental, health and safety requirements.
Method validationis not an individual’s responsibility. Successful acceptance of the validationparameters and performance criteria, by all parties involved, requires thecooperative efforts of several departments, including analytical development,QC, regulatory affairs and the individuals requiring the analytical data. Theoperating procedure or the Validation Master Plan (VMP) will clearly define theroles and responsibilities of each department involved in the validation ofanalytical methods. The scope of the method and its validation criteria are definedearly in the process. These include the questions like what analytes should bedetected, what are their expected concentration levels, what are the samplematrices, are there any expectation for interfering substances, and, if so,should they be detected and quantified or should not they, are there anyspecific legislative or regulatory requirements for the validation, wouldinformation be quantitative or qualitative, what are the required detection andquantitation limits for the selected method, what is the expected concentrationrange, what precision and accuracy is expected for the selected method, which typeof equipment should be used for the analysis, is the method is narrowed for onespecific instrument, or should it be used by all instruments of the same type,will the method be used in one specific laboratory or should it be applicablein all laboratories at one side or around the globe, what skills do the anticipatedusers of the method have etc.Characteristics ofthe method’s performance should be based on the intended use of the method.Validation of all analytical parameters that are available for a specifictechnique is not always necessary. For example, if the method is to be used forqualitative trace level analysis, there is no need to test and validate themethod’s limit of quantitation, or the linearity, over the full dynamic rangeof the equipment.
The method scopeshould also include the different types of equipment and the locations wherethe method will be run. For example, if the method is to be run on a specificinstrument in a specific laboratory, there is no need to use instruments fromother vendors or to include other laboratories in the validation experiments.In this way, the experiments can be limited to what is really necessary.Below table gives examples of which parametersmight be tested for a particular analysis task.