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Guidance Document on the Estimation of LOD and LOQ for Measurements in the Field of Contaminants in Feed and Food

Abstract: 
The European Union Reference Laboratory (EURL) for Polycyclic Aromatic Hydrocarbons (EURL PAH), the EURL for Heavy Metals in Feed and Food (EURL HM), the EURL for Mycotoxins (EURL Mycotoxins), and EURL for Dioxins and PCBs in Feed and Food aim to provide with this document guidance to official food control in the EU on the estimation of the limit of quantification of analytical methods for the determination of individual substances in the field of contaminants in feed and food. The document focusses on estimation of the limit of detection (LOD) and/or limit of quantification (LOQ) of polycyclic aromatic hydrocarbons (PAHs), heavy metals (HM), mycotoxins, and polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs). The concept presented here consists of two major routes: The first route responds to the requirements for determination of PAHs, HMs and Mycotoxins. The second route corresponds to PCDD/F and PCB analysis, where results are calculated as sum-parameters and expressed in toxic equivalents (TEQs), converting thereby congener concentrations together with estimated LOQs using toxic equivalency factor (TEFs) into TEQs. Due to the nature of this more complex procedure, emphasis is put in the area of PCDD/F and PCB analysis on the LOQs, while LODs are of minor consequence. Terminology in this guidance document was adapted to the chemical analysis of contaminants in feed and food; hence, some of the general terms defined and used in international standards were replaced by more specific terms applicable to analytical chemistry. The presented statistical-mathematical approach is based on elements taken mainly from DIN 32645:2008-11 (DIN 2008) and ISO 11843-2:2000 (ISO 2000). This document covers only quantitative methods of analysis. The authors believe that LOD and LOQ values derived from the application of the presented experimental methodologies converge to a certain degree. Estimation of LOD/LOQ values based on blank measurements, and from calibration data is described. Signal-to-noise ratios are applied in the area of PCDD/Fs and PCBs. Mathematical terms and statistical background are presented as well. This guide document shall be applied systematically if measurement results are used for monitoring purposes and exposure modelling. However, authors are aware that precise knowledge of LOD/LOQ may not be required when assessing compliance with maximum levels exceeding LOD/LOQ. This guidance document shall be applied if maximum levels and analysis results are close to the expected LOQ.
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