Voltammetric Determination of Nitronaphthalenes at a Silver Solid Amalgam Electrode

Abstract

Electrodes based on amalgam materials were re-introduced in electroanalytical chemistry in the year 2000, partially as reaction to unsubstantiated public fears of liquid mercury. In this publication, the voltammetric behavior of 1-nitronaphthalene and 2-nitronaphthalene was investigated at a mercury meniscus-modified silver solid amalgam electrode. The reduction mechanism in mixed neutral buffer-methanol medium includes the four-electron reduction to hydroxylaminoderivative followed by a two-electron reduction to the amine in acidic medium, similarly to mercury electrodes. In alkaline media, both compounds show the splitting of the main four-electron reduction peak typical for mercury electrodes in two new ones, the first one corresponding to a one electron reduction of the nitroderivative to the nitro radical anion, which was confirmed by microcoulometry. Using optimized conditions (differential pulse voltammetry, Britton-Robinson buffer pH 7.0 – methanol (9:1) medium) the calibration dependences are linear in the range of 2·10⁻⁷ (4·10⁻⁷) to 1·10⁻⁴ mol L⁻¹ for 1-nitronaphthalene (2-nitronaphthalene). After preconcentration of the analytes from drinking and river water samples using solid phase extraction the limit of determination was lowered to ∼3·10⁻⁸ mol L⁻¹.

Keywords:

• Cyclic voltammetry
• differential pulse voltammetry
• elimination voltammetry with linear scan
• 1-nitronaphthalene
• 2-nitronaphthalene
• silver solid amalgam electrode
• solid phase extraction

This work was financially supported by the Czech Ministry of Education, Youth and Sports (projects LC 06035 and MSM 0021620857). T. N. and B. Y. thank the Grant Agency of the Czech Republic (project 203/07/1195) and the Grant Agency of the Academy of Sciences of the Czech Republic (project IAA400400806).

Notes

^a Relative standard deviation; limit of determination for SPE-DPV at ^b m-AgSAE, and ^c HMDE (Pecková, 2006).