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%.