Trace Determination of Cd,Cu,Br,and Cl with Electrothermal Vaporization into a Helium Microwave-Induced Plasma

Abstract

An electrothermal vaporization (ETV) system was used to introduce aqueous samples into a helium microwave-induced plasma (He-MIP). The plasma was operated at 2.45 GHz and 500 W. The sample introduction system consisted of a carbon-cup-type electrothermal vaporizer in a glass chamber. A vapor restriction device was used to enhance the efficiency of sample transport to the plasma. For obtaining the best detection limits, matrix modifiers were used for the nonmetals. Lead nitrate as a matrix modifier was found to be particularly efficacious for the determination of bromide and chloride. Detection limits with the ETV-He-MIP with 15-ML samples were: Cd, 10 pg (0.6 ppb) at 228.8 nm; Cu, 30 pg (2 ppb) at 327.4 nm; Br, 300 pg (20 ppb) at 470.5 nm; and Cl, 120 pg (8 ppb) at 479.5 nm. Although the detection limits for the two metals studied are greater than those that have been obtained by ETV-ICP-AES, the detection limits for Br and Cl are the best that have been obtained by an ETV-AES technique to date in the UV-VIS spectral region. Linear responses of analytes were obtained for each element. Matrix effects of selected metals and nonmetals on chloride were investigated and found to be insignificant.