Detection of Heavy Metals By Anodic Stripping Voltammetry Using Nanocarbon Thin Film Electrodes in an Electrochemical Flow Cell

It is important to detect and quantify toxic heavy metals such as Pb in order to prevent damaging human health by their toxicities. A very small amount of heavy metals are included in food or water. The contamination of heavy metals into air, drinking waters, wastewaters and foods sometimes poses a serious threat to the problems on global health and environment. Conventional methods for the detection of heavy metals, such as atomic adsorption spectrometry, inductively coupled plasma mass spectrometry, and neutron activation analysis, require expensive and sophisticated instruments with the complicated sample preparation. Therefore, a simple, inexpensive and high performance analyzer for heavy metals is strongly desired. Anodic stripping voltammetry (ASV) is a standard methods for the analysis of heavy metals, because of several advantages, including high cost performance, high sensitivity resulted by its preconcentrating process, and suitability for a miniaturized system. In ASV, mercury film electrodes and the hanging mercury drop electrode had been widely used as the working electrode. However, more environmentally friendly electrode materials for use in ASV working electrodes has been strongly required, because of the increasing toxic risks on the used/disposed mercury. Here, an ASV-based Pb detection method using a nanocarbon thin film electrode with an electrochemical flow cell has been developed. The nanocarbon thin films were formed by unbalanced magnetron (UBM) sputtering, which is an exceptionally versatile technique for the deposition of high quality, well adhered films. UBM sputtering can be used to fabricate the hard films on silicon wafers that indicate the abrasion resistance and the sliding properties. The nanocarbon thin films comprise two types of carbon structure, diamond (sp 3 ) and graphite (sp 2 ), which have excellent properties including a wide potential window, the good electrode activity, and the superior stability. The sp 2 /sp 3 ratios of nanocarbon thin films were adjusted by the tuning of the ion irradiation energy between a silicon substrate and a carbon target. The surface fouling of the nanocarbon films were significantly suppressed because of extremely flat surface. It is the very suitable material for the ASV measurement of heavy metals such as Pb. A flow-type ASV-based Pb-detection method was studied. The flow cell was equipped with three electrodes consisted of nanocarbon film working electrode, an Ag/AgCl reference elec