Determination of cadmium, mercury and lead in soil samples by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry

Ultrasonic slurry sampling electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (USS-ETV-ID-ICP-MS) was applied to the determination of Cd, Hg and Pb in several soil samples. Palladium was used as the modifier. Since the sensitivities of the elements studied in soil slurry and aqueous solution were different, the isotope dilution method was used for the determination of Cd, Hg and Ph in selected soil samples. The influences of instrument operating conditions, slurry preparation and interferences on the ion signals and the accuracy and precision of isotope ratio determinations were reported. The isotope ratios of each element were calculated from the peak areas of each injection peak. The precision of the isotope ratio determinations was better than 4%. This method was applied to the determination of Cd, Hg and Pb in NIST SRM 2711 Montana soil reference material and several soil samples collected from the Kaohsiung area. The results for the reference sample NIST SRM 2711 Montana Soil agreed satisfactorily with the certified values. Results for other samples analysed by the isotope dilution method and the method of standard additions agreed satisfactorily. The precision was better than 5% and the accuracy was better than 2% with the USS-ETV-ID-ICP-MS method. Detection limits estimated from standard addition curves were in the ranges 4-24, 2-19 and 5-76 ng g(-1) for Cd, Hg and Pb, respectively, in different samples.