Electrochemical Preconcentration of Trace Metals for Simultaneous Multielement Determination by Inductively Coupled Plasma-Atomic Emission Spectrometry Utilizing Graphite-Cup Direct-Insertion Technique

Abstract

Electrochemical preconcentration of trace metals on a graphite cup for multielement determination by inductively coupled plasma-atomic emission spectrometry (ICP-AES) is described, where controlled potential electrolysis of trace metals in an electrolyte solution similar to seawater has been examined by the use of a newly designed Teflon® cell to allow cathodic deposition. The characteristic of the present system is to make deposition of trace metals only inside a graphite cup, which is inserted into the plasma for the analysis by ICP-AES with the use of a computer-controlled graphite-cup direct-insertion technique. The electrolysis parameters and the solution circulation rates during electrolysis and washing of deposit have been optimized by a univariate search method. With the present experimental system, it is possible to preconcentrate trace metals by a factor of 30 to 300, and to separate them from the major matrix consituents, such as NaCl, KCl, and MgCl2, in artificial seawater. The detection limits for Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn at the pg/mL level can be obtained with relative standard deviation of 2 to 11%.