A matrix-considering in-house validation concept for analytical methods is presented which takes into account the uncertainty due to matrix-and time-induced deviations. It is based on a variance component model for univariate quantitative measurement data that can be adapted to both screening and confirmation methods and to both zero-tolerance and threshold decisions. The model allows the calculation of critical concentrations for given a-errors and the calculation of the corresponding power function to evaluate the performance of an analytical method. The model is applied to a real-life validation experiment.
This article presents the results of a comparative study of nine commercially available ELISA test kits for clenbuterol and other beta 2-agonists currently being used in veterinary drug residue control of live and slaughtered animals in the European Union (EU). By determining measuring ranges, B/B0-50% values, inter- and intra-assay variations and cross-reactions as well as limits of detection (LOD) and recoveries for clenbuterol in bovine urine it could be demonstrated that a number of test kits showed considerable quality defects, reducing their applicability to residue control. LODs for urine assayed without a previous clean-up (as recommended by all kit manufacturers) varied between 1.2 and 11.1 ng clenbuterol per ml urine and did thus not meet the requirement of 1 ng/ml of the official residue control plans of the EU Member States.
This report presents the results of an investigation on the accumulation of beta-agonist residues in the retinal tissue of food producing animals. Three different species, calf, pig and turkey, were treated with six different beta-agonists and analysed for beta-agonist residues in retinal tissue applying a newly developed retina preparation procedure which provides sufficient sample material for multiple analyses. The results show that all selected beta-agonists accumulate in the retina, though in varying concentrations. The results are discussed on the basis of existing binding theories and with regard to their impact on the existing residue control strategy for beta-agonists.
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