Improvement scheme for the determination of arsenic species in mussel and fish tissues

Six interlaboratory studies were organised by the Standard, Measurement and Testing Programme of the European Commission on the determination of arsen ic species (arsenobetaine, arsenocholine, monomethylarsonic acid, dimethyla rsinic acid, As(III) and As(V)) in marine matrices and soil. A step-by-step approach was used and a meeting was held at the end of each study to help the participants to discover errors and to improve their analytical methods . The successive steps investigated the calibration procedures on various s olutions, the separation and derivatisation techniques on solutions and ext racts and the extraction on mussel and fish tissues. All materials used for the study were monitored for their stability. Verified calibration solutio ns and compounds were distributed to the participants in each exercise in o rder to trace calibration problems. The agreement between the results impro ved regularly and at the end of the six campaigns allowed the certification of a reference material of tuna-fish tissue (BCR-CRM 627) for its total ar senic, arsenobetaine and dimethylarsinic acid contents.