INFLUENCE OF DIGESTION PROCEDURES ON THE DETERMINATION OF LEAD AND CADMIUM LEVELS IN THE LAMINARIALE UNDARIA-PINNATIFIDA (WAKAME) BY FLAME ATOMIC-ABSORPTION SPECTROPHOTOMETRY

The Laminariale Undaria pinnatifida (Harvey) Suringar was digested by eight different wet and dry ashing procedures and the lead and cadmium contents determined by atomic absorption spectrophotometry (AAS). Aft er statistical analysis (Student and Fisher tests), the procedures usi ng hot nitric and perchloric acids were found to be significantly diff erent from the other mineralisation methods tested. A dry ashing proto col using sample calcination at 450 degrees C followed by ash treatmen t with hydrochloric acid and silica elimination by hydrofluoric acid g ives the best reproducibility. However, the validation of this ashing procedure for toxic minerals analyses from the Laminariales will requi re inter-laboratory collaborations and the use of an appropriate refer ence algal material. Undaria pinnatifida, the only seaweed artificiall y cultivated in Europe, and main brown seaweed (Wakame) consumed in th e world could be proposed as a future reference biological sample for Laminariales analyses.