On-line coupling of electrochemical preconcentration in trngsten coil electrothermal atomic absorption spectrometry for determination of lead in natural waters

摘要

A flow injection system was coupled to a tungsten coil electrothermal atomizer (150 W) for on-line separation and preconcentration of lead based on its electrochemical reduction on the atomizer surface. The electrochemical cell is built up inside the furnace by using a Pt flow-through anode and the atomizer itself as the flow-through cathode. The manifold and the tungsten coil power supply were controlled by a computer running a program written in Visual Basic, which was utilized in synchronism with the original software of the atomic absorption spectrometer. The flow-through anode (50 mm long, 0.7 mm i.d.) was inserted in tip of the autosampler arm by replacing the last section of the PTFE sample delivering tube. The tungsten coil atomizer and the counter electrode were easily connected to a d.c. power supply. An enrichment factor of 25 was obtained for lead after a 120-s electrodeposition for a sample flowing at 1.0 ml min~(-1). The method detection limit was 0.2 #mu#g l~(-1) Pb and the R. S. D. < 5% (N = 10 for 5 #mu#g l~(-1) Pb). Up to 2% m / v NaCl or KCl and 5% m / v CaCl_2 or MgCl_2 did not interfere on the separation and atomization of 5 #mu#g l~_(-1) Pb.