EDTA as the modifier for the determination of Cd, Hg and Pb in fish by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry

Ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS) has been applied to the determination of Cd, Hg and Pb in several fish samples. The influences of the instrument operating conditions and slurry preparation on the ion signals were reported. In this study, a relatively low vaporization temperature was used which separated the analyte from the major matrix components and improved the ion signals significantly. EDTA was used as the modifier to enhance the ion signals. Since the sensitivities of Cd, Hg and Pb in various fish slurries and aqueous solution were quite different, the standard addition method and isotope dilution method were used for the determination of Cd, Hg and Pb in these fish samples. This method has been applied to the determination of Cd, Hg and Pb in dogfish muscle reference material (DORM-2) and a swordfish sample purchased from the market. The analysis results agreed with the certified values. The precision between sample replicates was better than 14% with the USS-ETV-ICP-MS method. Detection limits estimated from standard addition curves were about 3-6, 3-9 and 6-7 ng g(-1) for Cd, Hg and Pb, respectively, in different samples.