Determination of Cd, Cu, and Zn in fish and mussel by AAS after ultrasound-assisted acid leaching extraction

An ultrasound-assisted solid–liquid extraction procedure by using diluted mixed acid solution was developed for determination of cadmium, copper and zinc in fish and mussel samples. The effects of several parameters such as nitric acid concentration, hydrochloric acid concentration, hydrogen peroxide concentration, leaching solution volume, and sonication time have been investigated. A 30-min sonication, 56 °C operating temperature and 6 mL of 1:1:1 HNO3(4 M):HCl(4 M):H2O2(0.5 M) were used for 0.5 g of dried sample. Cadmium and copper were determined by graphite furnace atomic absorption spectrometry, and zinc was determined by flame atomic absorption spectrometry. The results obtained from the proposed procedure were evaluated by comparison with the results obtained by microwave-assisted digestion. Ratio (%) of metal amount obtained from leaching technique to amount obtained from digestion technique for cadmium, copper and zinc ranged from 92% to 114% for fish and from 88% to 103% for mussel samples. The MDL were 0.02, 0.13 and 0.63 mg kg−1 for cadmium, copper and zinc, respectively. The accuracy of the developed method was investigated by analyzing a dogfish muscle certified reference material (DORM-2). Recoveries were obtained in the order of 80.9 ± 0.3 and 87.2 ± 0.6%.