Electrochemical sample matrix elimination for trace-level potentiometric detection with polymeric membrane ion-selective electrodes.
Potentiometric sensors are today sufficiently well understood and optimized to reach ultratrace level (subnanomolar) detection limits for numerous ions. In many cases of practical relevance, however, a high electrolyte background hampers the attainable detection limits. A particularly difficult sample matrix for potentiometric detection is seawater, where the high saline concentration forms a major interfering background and reduces the activity of most trace metals by complexation. This paper describes for the first time a hyphenated system for the online electrochemically modulated preconcentration and matrix elimination of trace metals, combined with a downstream potentiometric detection with solid contact polymeric membrane ion-selective microelectrodes. Following the preconcentration at the bismuth-coated electrode, the deposited metals are oxidized and released to a medium favorable to potentiometric detection, in this case calcium nitrate. Matrix interferences arising from the saline sample medium are thus circumvented. This concept is successfully evaluated with cadmium as a model trace element and offers potentiometric detection down to low parts per billion levels in samples containing 0.5 M NaCl background electrolyte.
Chumbimuni-Torres
Karin Y
KY
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
Calvo-Marzal
Percy
P
Wang
Joseph
J
Bakker
Eric
E
D002104:Cadmium / Q000032:analysis; D004563:Electrochemistry; D017736:Ion-Selective Electrodes / Q000592:standards*; D008567:Membranes, Artificial; D011108:Polymers; D011199:Potentiometry / Q000379:methods*; D012623:Seawater / Q000737:chemistry*; D014131:Trace Elements / Q000032:analysis*
D008567:Membranes, Artificial; D011108:Polymers; D014131:Trace Elements; D002104:Cadmium