Development of a method for the determination of inorganic cadmium and cadmium metallothioneins in fish liver by continuous preconcentration on fullerene and flame atomic absorption spectrometry

Abstract

The adsorptive potential of C₆₀ fullerene for the preconcentration of metallothionein-bound cadmium (Cd-MT) traces was assessed for the first time in this work. A simple flow injection system for the on-line preconcentration of Cd-MT was developed. The compounds were directly retained on the sorbent column and subsequently eluted, by hydrolysis of the complexes with diluted HNO₃, and the cadmium was transferred to a flame atomic absorption spectrometer. Total cadmium (inorganic and Cd-MT) was also determined by preparing the sample in acid medium and complexing total cadmium with Na-DDC. The neutral chelates of cadmium, retained also on C₆₀, were eluted with IBMK and transferred to the atomic absorption instrument. By the difference between both determinations, inorganic and organometallic forms of cadmium could be distinguished. The analytical figures of merit of the proposed method are: linear range, 0.3–12 ng ml⁻¹ (using 10 ml of sample); limit of detection, 0.1 ng ml⁻¹ and precision (RSD), ca. 4%. No interferences from metals such as Zn, Fe, Pb, Cu and Hg, as inorganic salts, were observed in the determination of total Cd. The method was applied to the determination of inorganic and organometallic cadmium compounds in spiked fish liver samples, with acceptable recoveries.