Determination of polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) in food and feed using a bioassay : result of a validation study

It is estimated that more than 90% of dioxins consumed by humans come from foods derived from animals. The European Commission through a Council Regulation (No 2375/2001) and a Directive (2001/102/EC), both revised by the Commission Recommendation (2002/201/EC), has set maximum levels for dioxins in food and feedstuffs. To implement the regulation, dioxin-monitoring programs of food and feedstuffs will be undertaken by the Member States requiring the analysis of large amounts of samples. Food and feed companies will have to control their products before putting them into the market. The monitoring for the presence of dioxins in food and feeds needs fast and cheap screening methods in order to select samples with potentially high levels of dioxins to be then analysed by a confirmatory method like HRGC/HRMS. Bioassays like the DR CALUX {sup registered} - assay have claimed to provide a suitable alternative for the screening of large number of samples, reducing costs and the required time of analysis. These methods have to comply with the specific characteristics considered into two Commission Directives (2002/69/EC; 2002/70/EC), establishing the requirements for the determination of dioxin and dioxin-like PCBs for the official control of food and feedstuffs. The European Commission's Joint Research Centre is pursuing validation of alternative techniques in food and feed materials. In order to evaluate the applicability of the DR CALUX {sup registered} technique as screening method in compliance with the Commission Directives, a validation study was organised in collaboration with CSL and RIKILT. The aim of validating an analytical method is first to determine its performance characteristics (e.g. variability, bias, rate of false positive and false negative results), and secondly to evaluate if the method is fit for the purpose. Two approaches are commonly used: an in-house validation is preferentially performed first in order to establish whether the method is mature enough for being tested in a collaborative trial. A number of reports have described the in-house validation of the DR CALUX {sup registered} -assay, thus allowing proceeding to the second step, an interlaboratory trial. In this step a set of chicken feeds and fish oil samples at four different levels of contamination were analysed by both experienced and newly trained laboratories.