Ma. Nolan et Sp. Kounaves, Microfabricated array of iridium microdisks as a substrate for direct determination of Cu2+ or Hg2+ using square-wave anodic stripping voltammetry, ANALYT CHEM, 71(16), 1999, pp. 3567-3573
In this paper, we report for the first time the characterization and separa
te electrochemical determinations of Cu2+ and Hg2+ directly on a microlitho
graphically fabricated array of iridium ultramicroelectrodes (Ir-UMEA). Squ
are-wave anodic stripping voltammetry was used to optimize experimental par
ameters such as supporting electrolyte, square-wave frequency, and depositi
on time and potential. Reproducible stripping peaks were obtained for solut
ions containing low parts per billion (ppb) concentrations of either metal.
Excellent linearity was obtained for Cu2+ in the 20-100 ppb range and for
Hg2+ in the 1-10 ppb range when the bare iridium substrate was used. Detect
ion limits were calculated to be 1 ppb (0.1 M KNO3 and 0.1 M HClO4, deposit
ion time 180 s) and 5 ppb (0.1 M H2SO4, deposition time 120 s) for Cu2+ (S/
N = 3) and 85 ppt for Hg2+ (deposition time 600 s). The experimental detect
ion limits were determined to be 5 ppb for Cu2+ (deposition time 180 s) and
100 ppt for Hg2+ (deposition time 600 s). Interference studies were perfor
med, and it was determined that Pb, Zn, and Cd had little or no influence o
n the copper signal. Tap water and spring water samples were analyzed for c
opper, and good agreement was obtained with conventional methods. An unexpl
ained effect of chloride ions on the iridium surface was noted. Further inv
estigation;by atomic force microscopy determined that changes on the surfac
e occurred but could be eliminated when chloride leakage from the reference
electrode was minimized. The solid state construction of the Ir-UMEA makes
it a prime candidate for use in determining Cu(II) and Hg(II) in chemicall
y harsh environments.