Organic acids as the modifier to determine Zn, Cd, Tl and Pb in soil 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 determina tion of Zn, Cd, T1 and Pb in several soil samples. A mixture of 1% m/v EDTA and 1.5% m/v of ascorbic acid was used as the modifier to enhance the ion signals. The influences of instrument operating conditions and slurry prepa ration on the ion signals were reported. In this study, a relatively low va porization temperature was used which separated the analyte from the major matrix components and improved the ion signals significantly. With ETV samp le introduction device, spectroscopic and nonspectroscopic interferences we re alleviated significantly. Since the sensitivities of Zn, Cd, T1 and Pb i n various soil slurries and aqueous solution were different, standard addit ion method and isotope dilution method were used for the determination of Z n, Cd, T1 and Pb in these soil samples. This method has been applied to the determination of Zn, Cd, T1 and Pb in NIST SRM 2711 Montana soil reference material and several soil samples collected from Kaohsiung area. The analy sis results were agreed with the certified values. The precision between sa mple replicates was better than 9% with USS-ETV-ICP-MS method. Detection li mits estimated from standard addition curves were about 260-620, 3-5, 0.3-1 and 9-20 ng g(-1) for Zn, Cd, T1 and Pb, respectively, in different sample s. (C) 2001 Elsevier Science B.V. All rights reserved.