Determination of Ca,K, Mg and Fe in four fish species by FAAS

A method for determining calcium(Ca), potassium(K), magnesium(Mg)and iron(Fe)in four fish species was optimized and validated. It included microwave mineralization of the samples and subsequent quantification by flame atomic absorption spectroscopy(FAAS)with Zeeman-effect background correction. Using HNO3(65%)and H2O2(33%)as extraction solutions, the optimal conditions of extraction were established as follows:0. 5 g of sample mass;microwave time program of 300 W/5 min and 600 W/5 min. The method was free of matrix interferences. The linear correlation coefficients were ≥0. 9991, the recovery percentage of analytes was from 99. 31% to 103. 70% and the RSD(relative standard deviation)was lower than 2. 06%. The detection limits obtained were 32. 3, 43. 2, 14. 0 and 68. 6ngmL-1 for Ca, K, Mg and Fe in FAAS respectively. It is shown that the method is rapid, simple, sensitive and accurate. The method was applied to the studies of digestibility and measurement of these nutrients in samples of fish collected from Norway, Japan and China.