镉(Ⅱ)-碘化钾-VBB体系的共振散射光谱及分析应用

Resonance Scattering Spectra of Cadmium(Ⅱ)-Potassium Iodide-VBB System and Its Analytical Application

镉是一种重金属污染物,它能通过食物链进入生物体内,从而影响人类健康,因此对环境中镉的检测引起了人们的广泛关注。在p H=4的弱酸性条件下,过量I^-与Cd^(2+)形成[CdI4]2^-,在疏水作用力和静电引力共同作用下进一步与维多利亚蓝B(VBB)形成三元离子缔合物[VBB]_2[CdI_4],该体系的共振瑞利散射(RRS)、二级散射(SOS)和倍频散射(FDS)信号均有明显增强,最大散射波长分别位于623 nm(RRS)、696 nm(SOS)、343 nm(FDS)处。通过实验条件优化,ΔI与Cd^(2+)浓度在一定范围内呈良好线性关系,且检出限分别为0.28μg/L(RRS)、0.17μg/L(SOS)、0.39μg/L(FDS)。将此方法用于实验室废水、涪江河水和自来水中Cd^(2+)的测定,回收率在95.1%~107.3%之间,效果令人满意。同时还对反应机理进行了初步讨论。

Cadmium is a heavy metal pollutant that can be stored in organisms through the food chain, thus affecting human health. Therefore, the detection of cadmium in the environment has aroused wide concern. In weak acidic environment of pH4, excessive I^-can react with Cd^2+to form [CdI4]^2-, it further reacts with Victoria Blue B(VBB) to form ternary ion association complex [VBB]2[CdI4] because of hydrophobic force and electrostatic attraction. In addition, resonance Rayleigh scattering(RRS), secondary scattering(SOS) and frequency-doubling scattering(FDS) signals of the system have been enhanced obviously, and the biggest scattering wavelength located at 623 nm(RRS), 696 nm(SOS) and 343 nm(FDS), respectively. Under the optimum experimental conditions, enhanced peak signal(ΔI) has a good linear relation with the concentration of Cd^2+within a certain range. The detection limits were 0.28 μg/L(RRS), 0.17 μg/L(SOS) and 0.39 μg/L(FDS), respectively. This method has been used for the determination of Cd2+in laboratory wastewater, Fujiang river water and tap water samples with recoveries of 95.1%107.3%. Moreover, the reaction mechanism has also been discussed preliminarily.