1. Interlaboratory Comparison on Dioxins in Food 2007, eighth round of an international study (in cooperation with the Norwegian Institute of Public Health)

A cooperation between the Norwegian Institute of Public Heakth and the CRL for Dioxins and PCBs allowed the participation of NRLs in this proficiency test on three different matrices and analyte solutions:
- Salmon filet
- Chicken meat
- Butter

Further evaluation of the results of participating NRLs was performed by the CRL and compared to the individual and consensus concentrations of all participating laboratories.

2. Proficiency test on the determination of PCDD/Fs, PCBs (dioxin-like PCBs and indicator PCBs) and pentachlorophenol (PCP) in guar gum 2008

The proficiency test on the determination of PCDD/Fs, PCBs and PCP in guar gum was organized by the CRL for Dioxins and PCBs in Feed and Food in cooperation with the CRL for Residues of Pesticides - Single Residue Methods, Stuttgart, Germany. The concentration range and congener pattern of the two PT samples reflected the range of contamination of guar gum originating from India in 2007. More than 50 laboratories worldwide participated in this PT analyzing PCDD/Fs in both samples.
A summary of the PT and the results for PCDD/Fs was presented at the Dioxin conference in Beijing 2009 and published in Organohalogen Compounds.

3. Proficiency test on the determination of PCDD/Fs, PCBs (dioxin-like PCBs and indicator PCBs) in Fish Oil 2008

The proficiency test on the determination of PCDD/Fs, dioxin-like PCBs and indicator PCBs in fish oil was organized by the CRL in 2008. 51 national reference laboratories (NRLs) and official laboratories from EU member states reported results for the required parameters using screening and confirmatory methods. The fish oil sample contained WHO-PCDD/F and WHO-PCB-TEQ concentrations in the range of maximum and action levels defined for marine oils as foodstuff in Commission Regulation (EC) 1881/2006 and Commission Recommendation 2006/88/EC. A summary of the PT results was presented at the Dioxin Conference in Beijing 2009 and published in Organohalogen Compounds.

4. Proficiency test on the determination of PCDD/Fs, PCBs (dioxin-like PCBs and indicator PCBs) in Canned Sausage (Pork) 2009

The proficiency test on the determination of PCDD/Fs and PCBs in pork sausage was organized by the CRL between January and April 2009. 77 NRLs and official laboratories from EU member states reported results for the requested parameters. Besides the determination of PCDD/Fs and PCBs participants were also asked to report the lipid content of the sample. The WHO-PCDD/F- and WHO-PCB-TEQ concentrations were in the range of maximum levels defined for meat and meat products of pigs (Commission Regulation (EC) 1881/2006). More than 70 % of the laboratories reported results for the sum parameters WHO-PCDD/F-PCB-TEQ, WHO-PCDD/F-TEQ, WHO-PCB-TEQ and sum of six indicator PCBs as well as for the lipid content within a range of ± 2 z-scores of the assigned value.

1. Interlaboratory study on PCDD/Fs in Sepiolite 2006

The CRL for Dioxins and PCBs in Feed and Food perfomed a comprehensive study on extraction methods for PCDD/Fs in the mineral clay sepiolite in 2006. 17 laboratories participated in the study using well defined and routinely used extraction methods, focusing especially on the extraction solvents, methods and the sample pre-treatment before extraction. As a main conclusion from this comprehensive study, including further tests at the CRL, the best suitable extraction method for sepiolite is toluene mixed with a substantial fraction of a polar solvent. The results and conclusions of the study were also presented at the Dioxin conference in Tokyo 2007 and published in Organohalogen Compounds.

2. Interlaboratory study on PCDD/Fs in Fullers Earth and Maganese Oxide 2007

The process of harmonization of extraction methods for the determination of PCDD/Fs and PCBs in mineral feed, which was initiated with the interlaboratory study on extraction techniques for sepiolite in 2006, was continued with an interlaboratory study on extraction methods for fullers earth and manganese oxide. This study comprises the interlaoratory study with 23 participating laboratories and additional comprehensive tests at the CRL. The results of this study and main conclusions were presented at the Dioxin conference in Birmingham 2008 and summarized in an abstract in Organohalogen Compunds.

• Interlaboratory study on harmonization of extraction procedures for determination of PCDD/F and PCB in feedingstuff (Organohalogen Compd 70, 2008)