Dugo G, La Pera L, Lo Turco V, Di Bella G
Department of Organic and Biological Chemistry, University of Messina, Salita Sperone 31, 98166 Messina, Italy.
Chemosphere. 2005 Dec;61(8):1093-101. doi: 10.1016/j.chemosphere.2005.03.049. Epub 2005 Apr 26.
The purpose of this research was to develop a sensitive and accurate chronopotentiometric method at a gold film electrode, to determine trace and ultra trace levels of As(III) and As(V) in alimentary and environmental water systems. As(III) was directly determined in the aqueous matrix at a deposition potential of -300 mV for 180 s and at a constant anodic current of 2.5 microA, without any sample pre-treatment; moreover the chronopotentiometric method did not require a time-consuming de-oxygenation step prior to the analysis. A 3M HCl solution was chosen as the best stripping medium. The direct analysis of As(V) required the application of a high negative over-potential and, thus, measurements were characterized by poor reproducibility; therefore As(V) was determined after reduction to As(III) with KI in a strong hydrochloric acid solution. Under the optimised electrochemical conditions, detection limits of 0.08 microg As(III) l(-1) were achieved and no significant interferences from Cd, Cu, Pb, Zn and organic substances were observed. As(V) was the most abundant species in all the studied environmental and alimentary aqueous matrices. Amongst the beverages, tea and coffee presented the As(V) highest concentration ranges (934-1740 microg l(-1) and 850-1290 microg l(-1), respectively) while bottled mineral water the lowest (<1.61 microg l(-1)); whereas As(III) levels lower than 5.0 microg l(-1) were detected only in wine samples.
本研究的目的是开发一种在金膜电极上灵敏且准确的计时电位法，用于测定食品和环境水体系中痕量和超痕量水平的As(III)和As(V)。As(III)在水基质中于 -300 mV的沉积电位下沉积180 s，并在2.5 μA的恒定阳极电流下直接测定，无需任何样品预处理；此外，计时电位法在分析前不需要耗时的脱氧步骤。选择3M HCl溶液作为最佳的溶出介质。As(V)的直接分析需要施加高负过电位，因此测量的重现性较差；因此，在强盐酸溶液中用KI将As(V)还原为As(III)后进行测定。在优化的电化学条件下，实现了0.08 μg As(III) l⁻¹的检测限，未观察到Cd、Cu、Pb、Zn和有机物的明显干扰。As(V)是所有研究的环境和食品水基质中含量最丰富的物种。在饮料中，茶和咖啡中As(V)的浓度范围最高（分别为934 - 1740 μg l⁻¹和850 - 1290 μg l⁻¹），而瓶装矿泉水中最低（<1.61 μg l⁻¹）；而仅在葡萄酒样品中检测到低于5.0 μg l⁻¹的As(III)水平。
