Only the FDA has segregated the levels of method validation into four standard levels of performance, in which the key validation parameters for each level are well identified. The method validation levels consist of: (1) a single laboratory validation for emergency use or a method developed for a specific analyte in a matrix that is not previously validated, (2) a single laboratory validation for routine regulatory testing in which the originating lab has conducted a comprehensive validation study, (3) a multi-laboratory validation which employs a minimum of one collaborating lab-oratory in addition to the originating laboratory and (4) a full AOAC Collaborative study that can be adopted by the AOAC as a fully collaborated method. This allows the validation method to be performed more accurately by assigning the numbers of lab-oratories involved, matrix sources per matrix, spiking levels and number of replicates to be performed [18]. Unlike the FDA, AOAC,IUPAC and Eurachem describe the definition in more detail, and include a method of determining and assessing each characteristic of each parameter in the validation method.