SPEEDING-UP OF A 3-STAGE SEQUENTIAL EXTRACTION METHOD FOR METAL SPECIATION USING FOCUSED ULTRASOUND

The three-stage sequential extraction procedure, proposed by the Europ ean Community Bureau of Reference (BCR), has been applied for speciati on of copper, chromium, nickel, lead and zinc in a sludge sample colle cted from an urban wastewater treatment plant. The conventional BCR se quential extraction method has been modified, in each stage, applying ultrasonic energy by means of a probe (handling at an adequate sonicat ion power and time) in order to shorten the required operation time. E xtractable metal contents obtained by both the conventional and the ac celerated ultrasonic extraction method, were measured by Flame-Atomic Absorption Spectrometry. Results obtained in each fraction by both met hods were statistically compared (P=0.95) for all the studied elements and no significant differences were found except for chromium and zin c in the third fraction (oxidisable). For all metals the extraction pe rcentage was>95%. The proposed accelerated sequential extraction metho d could be a valid alternative to the conventional shaking with a much shorter operating time. (C) 1998 Elsevier Science B.V.