应用聚丙烯酸钠为结合相的薄膜扩散梯度技术测定水中Cd2+

摘要

研究了以聚丙烯酸钠(PAAS)溶液为结合相的薄膜扩散梯度(DGI)装置(PAASDGT装置)用于测定水中Cd2+的分析方法.考察了DGT技术的有效性、PAAS DGT装置饱和累积容量以及本体溶液pH值、离子强度对PAAS DGT装置累积Cd2+的影响.实验表明:PAAS DGT装置的饱和累积容量为278.88 mg/L,本体溶液pH值在4～10和离子强度在0.000 1～0.1 mol/L范围内基本不影响PAAS DGT对Cd2+的累积,以PAAS为结合相的DGT装置对合成水中Cd2+ 的累积量与时间呈线性关系,线性相关系数r为0.999 6,回收率为99.25%,RSD%为1.96%.PAAS DGT装置与火焰原子吸收光谱法相结合可用于水样中Cd2+的测定,测量结果与镉的离子选择电极法(Cd-ISE)相符,并具有比Cd-ISE更低的检出浓度.%The free cadmium ion in water was measured by using sodium polyacrylate (PAAS) as binding phase in the diffusive gradients in thin-films (DGT) device(PAAS DGT device). Multiple problems were discussed, such as the effect of DGT, the saturated cumulative capacity of PAAS DGT device, the pH value of bulk solution and the effect of ion intensity on the cumulation of Cd2+ in PAAS DGT device. The saturated cumulative capacity of PAAS DGT device were 278. 88 mg/mL. The cumulation capacity of PAAS DGT device for Cd2+ was not affected when the bulk solution was at pH 4-10 and ion intensity was from 0. 0001 mol/L to 0. 1 mol/L. The linear correlation coefficient (r) of cumulated mass of Cd2+ in synthetic water with time was 0. 999 6 with the recovery of 99. 25 ％ and the relative standard deviation (RSD) of 1. 96 ％. It was proved that PAAS DGT device could be applied to the determination of free Cdz+ ion in combination with flame atomic absorption spectrometry.The results were consistent with those by Cd ion selective electrode (Cd-ISE) , and the detection concentration was even lower.