ABSTRACT
Analysts are accountable for the quality of their work and responsible for producing correct results, which may provide the basis for making decisions with serious consequences. Fully validated methods should be applied, and their acceptable daily performance characteristics should be regularly verified with appropriate internal quality control carried out within well-designed quality assurance programmes. Very good and detailed guidance documents on the method validation and quality control of the pesticide residues analysis has been prepared and published by the Codex Committee on Pesticide Residues, the European Union, and several National Authorities. These documents are regularly updated and freely available from the Internet. This chapter refers to these relevant guidance documents, including the procedures for confirming the compliance with specified performance criteria, but it does not attempt to repeat part of them. Instead, it pays emphasis to some areas which are the primary precondition of exact results and often neglected by the analysts, such as obtaining good samples, performing correctly the subsampling, sample size reduction, testing the homogeneity of the comminuted matrix, testing the stability of pesticide residues during shipping, storage and sample processing, and accuracy of analytical standard solutions. Further on, the sources of bias and uncertainty of the measurement results, the methods for their quantification, and potential reduction are discussed.
