Parameter Optimizations for Square-Wave Anodic Stripping Voltammetry for Cadmium Detection Using Boron-Doped Diamond Ele
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Parameter Optimizations for Square-Wave Anodic Stripping Voltammetry for Cadmium Detection Using Boron-Doped Diamond Electrodes with Different Doping Levels André F. Sardinha1,2, Lilian M. Silva1, Neidenêi G. Ferreira1 1 Associated Laboratory of Sensors and Materials, National Institute for Space Research, São José dos Campos, SP, 12227-010, Brazil. 2 Federal University of São Paulo, São José dos Camos, SP, 12247-014, Brazil.
ABSTRACT The parameter optimizations of square-wave anodic stripping voltammetry using boron doped diamond (BDD) electrodes with different doping levels for cadmium detection were studied. The optimized relation among the peak current with the pulse frequency, the amplitude, and the potential increment for highly (1019 cm-3) and heavily BDD (1021 cm-3) electrodes was considered. The peak currents were measured around -0.75 V vs. Ag/AgCl for Cd2+ concentration ranged from 1 to 20 ppb. Both BDD films provided detection limits lower than 5 ppb showing that these electrodes are suitable to use in a mercury-free method to determine cadmium trace levels in water.
INTRODUCTION Cadmium (Cd) is considered a highly toxic heavy metal, even at trace levels, and extended environmental exposure to it can cause serious health issues such as nephrotoxicity, bone demineralization, and cancer [1]. Cd monitoring with adequate selectivity, sensitivity and reproducibility is essential for the rules governing the maximum permissible exposure levels of these heavy metals in water to protect public health. Boron doped diamond (BDD) electrodes have been extensively studied due to their attractive electrochemical properties that have favored the evolution of their use to detect a variety of analytes, including heavy metals traces as well as pesticide determinations substituting the mercury electrodes in analytical techniques [2,3]. Regarding Cd detection, Sugitani et al. have studied an interesting methodology for the selective cadmium detection by controlling the diff usion profile of interference species [4]. Show et al. have studied differential pulse ASV for Pb(II) Cd(II) and (AgI) using boron doped nanocrystalline diamond. They showed that despite the intermetallic compound formation a linear response range occurred [5]. Zhang et al. have discussed with successes Cd trace levels determination by square wave anodic stripping voltammetry (SWASV) using an ultrasound power for solution stirring [6]. Also, McGrew and Swain have conducted a comparative study using Hg and BDD electrodes for heavy metal detections and discussed superior BDD properties [7]. In this work, BDD with two doping levels were produced and characterized. They were applied to Cd detection in water using SWASV. The voltammetric parameters were optimized for both electrodes taking into account the following results: (1) SWV curves for the net current (I), its forward (If) and its backward (Ib) components, (2) the dependence of net peak current of reversible reaction as a function of the frequency square-root, (3) the dependence of the net peak curren
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