Analytical Sciences

Effect of the sp²/sp³ Ratio in a Hybrid Nanocarbon Thin Film Electrode for Anodic Stripping Voltammetry Fabricated by Unbalanced Magnetron Sputtering Equipment

Hiroyuki YANAGISAWA,*,** Ryoji KURITA,* Tomoyuki KAMATA,* Kyoko YOSHIOKA,* Dai KATO,* Ayumi IWASAWA,*** Tetsuya NAKAZATO,*** Masaki TORIMURA,*** and Osamu NIWA*,**

*National Institute of Advanced Industrial Science and Technology (AIST), Central 6, 1-1-1 Higashi, Tsukuba 305-8566, Japan
**Institute of Materials Science, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Japan
***National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba 305-8569, Japan

The effect of the sp²/sp³ ratio in an unbalanced magnetron sputtered nanocarbon film electrode was studied for determining Cd²⁺ and Pb²⁺ by anodic stripping voltammetry (ASV). The signal-to-noise ratio in the ASV measurement improved as the sp³ concentration in the carbon film increased because the noise current decreased with the increasing sp³ concentration. The detection limits with a carbon film containing 50% sp³ were 0.25 and 1.0 μg L⁻¹ for Cd²⁺ and Pb²⁺ with high repeatability (Cd: 4.6% and Pb: 6.4%, n = 3). For a real sample measurement, a pretreatment system combining a photooxidation reactor and a cation exchange column was used to eliminate the interference from EDTA and Cu²⁺, which forms a stable complex or alloy with Cd²⁺ and Pb²⁺. More than 99% of the interference was eliminated, and accurate signal currents for Cd²⁺ and Pb²⁺ were successfully obtained with the pretreatment system.

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