Redox magnetohydrodynamic enhancement of stripping voltammetry: toward portable analysis using disposable electrodes, permanent magnets, and small volumes
by Weston, Melissa Christine; Anderson, Emily Clary; Arumugam, Prabhu U.; Narasimhan, Padhmodhbhava Yoga; Fritsch, Ingrid
The use of redox magnetohydrodynamics (MHD) to enhance the anodic stripping voltammetry (ASV) response of heavy metals has been investigated, with respect to achieving portability: disposable electrodes consisting of screen-printed carbon (SPC) on a low temperature co-fired ceramic (LTCC) substrate, small volumes, and permanent magnets. The analytes tested (Cd2+, Cu2+, and Pb2+) were codeposited on SPC with Hg2+ to form a Hg thin film electrode. High concentrations of Fe3+ were used to produce a high cathodic current which generates a significant Lorentz force in the presence of a magnetic field. This Lorentz force induces solution convection during the deposition step, enhancing the mass transport of analytes to the electrode and increasing their preconcentrated quantity in the mercury thin film. Therefore, larger ASV peaks and improved sensitivities are obtained, compared to analyses performed without a magnet. The effects on ASV signal of varying Hg2+ concentration (0.10 and 1.0 mM), deposition time ( 10 - 600 s), and electrode surface roughness were investigated. In addition, analyses were performed using a real lake water matrix. By using the disposable LTCC-SPC working electrodes in small volumes ( 150 mu L) and with small permanent magnets (0.78 T), peak areas were increased by 75% when compared to the signal obtained in the absence of a magnetic field. A limit of detection of 25 nM for Cd2+ was observed with only a 1 min preconcentration time.
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