Determination of Methyl Violet 2B using Polarographic and Voltammetric Methods at Mercury Electrodes

ABSTRACT

Direct current tast polarography and differential pulse polarography at a dropping mercury electrode and direct current voltammetry, differential pulse voltammetry, and differential pulse adsorptive stripping voltammetry at a hanging mercury drop electrode were employed for the electrochemical characterization and determination of methyl violet 2B in buffered aqueous media and model water samples. The optimum medium for all techniques was 0.04 mole per liter Britton-Robinson buffer at pH 4.0. The limits of quantification for methyl violet 2B were 1.7 micromole per liter (direct current tast polarography at the dropping mercury electrode), 0.16 micromole per liter (differential pulse polarography at the dropping mercury electrode), 65 nanomoles per liter (direct current voltammetry at the hanging mercury drop electrode), and 45 nanomoles per liter (differential pulse voltammetry at the hanging mercury drop electrode). The lowest limit of quantification of 13 nanomoles per liter was obtained using differential pulse adsorptive stripping voltammetry at the hanging mercury drop electrode with an accumulation potential of −500 millivolts and an accumulation time of 600 seconds. The optimized conditions were employed for the determination in drinking (limit of quantification of 40 nanomoles per liter) and river (limit of quantification of 20 nanomoles per liter) water.

KEYWORDS:

• Differential pulse adsorptive stripping voltammetry
• differential pulse polarography
• differential pulse voltammetry
• direct current tast polarography
• direct current voltammetry
• mercury electrodes
• methyl violet 2B