STUDY OF INTERFERENCES FROM NA AND CL USING ETV-ICP-MS

The effect of Cl, Na and NaCl on the signal of the isotopes Ti-46, Ti- 47, Ti-49, Cr-53, Fe-54, Mn-55, Ni-62, were investigated comparing pne umatic nebulization versus electrothermal vaporization (ETV) as sample introduction systems for analysis by inductively coupled plasma mass spectrometry (ICP-MS). Signal suppression by Na and polyatomic ion int erferences produced by Na and Cl were quantified using pneumatic nebul ization. Using ETV, the Na and Cl polyatomics, which interfere at the m/z ratio of most of the isotopes, were not formed to a significant ex tent for concentrations up to 3000 mu g/ml Na and Cl of the potential interferents. However, above this concentration, significant signal su ppression was found for Zn-67 and Ge-70, even a high pyrolysis tempera ture. High blank values were found for Cl-53 and Fe-54 due to the form ation of ions involving H, C, and N. Two certified seawater samples we re analyzed directly using nitric acid as a chemical modifier and matr ix matching external calibration. The values obtained for Ni, Cu, V, f ind Mn agreed well with the certified concentrations. For As and Se, p alladium nitrate was used as the modifier. The calibration was perform ed by the method of standard additions. Selenium could not be measured in the seawater samples since the concentrations were below the limit of quantitation (LOQ).