Method performance terms trueness

The methods It is advised that, prior to the certification measurements, the participants discuss their methods so that all participants have confidence in each others methods and there is a good level of agreement between laboratories. As it is preferred to certify on the basis of the agreement between different methods applied in different laboratories, a proposal should indude, where relevant and possible, a group of laboratories offering a range of widely different measurement methods. Each laboratory should use well established method(s), with which it can demonstrate adequate performance in terms of trueness and in terms of reproducibility. 

If analytical methods are validated in inter-laboratory validation studies, documentation should follow the requirements of the harmonized protocol of lUPAC. " However, multi-matrix/multi-residue methods are applicable to hundreds of pesticides in dozens of commodities and have to be validated at several concentration levels. Any complete documentation of validation results is impossible in that case. Some performance characteristics, e.g., the specificity of analyte detection, an appropriate calibration range and sufficient detection sensitivity, are prerequisites for the determination of acceptable trueness and precision and their publication is less important. The LOD and LOQ depend on special instmmentation, analysts involved, time, batches of chemicals, etc., and cannot easily be reproduced. Therefore, these characteristics are less important. A practical, frequently applied alternative is the publication only of trueness (most often in terms of recovery) and precision for each analyte at each level. No consensus seems to exist as to whether these analyte-parameter sets should be documented, e.g., separately for each commodity or accumulated for all experiments done with the same analyte. In the latter case, the applicability of methods with regard to commodities can be documented in separate tables without performance characteristics. 

There is some help in terms of setting some of the performance characteristics. The European Community implementing Council Directive 96/23/EC has considered the level of bias (trueness) and precision appropriate for analytical methods used to monitor the concentrations of certain substances and residues of the substances in animal products for concentrations ranging from 1 ig kg-1 to 1 mg kg l. Their recommendations for the trueness and precision of analytical methods are shown in Tables 4.2 and 4.3, respectively. However,... 

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