聚合物膜钙离子选择性电极检测游离钙和总钙浓度

摘要

利用聚合物膜钙离子选择性电极,通过使用不同的内充液,分别实现了游离钙和在络合剂EDTA和腐殖酸存在下总钙浓度的检测.结果表明,采用0.1 mol·L-1 NaCl+1×10-3 mol·L-1 CaCl2作为内充液的电极,可以实现低至1×10-6 mol·L-1 游离钙活度的检测;而采用1×10-3 mol·L-1 CaCl2+5×10-2 mol·L-1 Na2EDTA (pH=9.0)作为内充液的电极,在1×10-6~1×10-5 mol·L-1 Ca2+浓度范围内有超能斯特现象发生,电位差值为180 mV,且在该范围内电位响应与总钙浓度呈线性相关,与游离钙活度无关.该研究为进一步开展形态分析提供了一种简单、有效的技术手段.%Two kinds of calcium-selective polymeric membrane electrodes (Ca2+-ISEs) with different inner filling solutions for the detection of free and total Ca2+concentrations in the presence of EDTA and humic acid are described.The results indicate that,the free Ca2+ activity,as low as 1×10-6 mol·L-1,could be detected by Ca2+-ISE (Ⅰ) with the inner filling solution of 0.1 mol·L-1NaCl and 1×10-3 mol·L-1 CaCl2,while Ca2+-ISE(Ⅱ) with the inner filling solution of 1×10-3 mol·L-1 CaCl2 and 5×10-2 mol·L-1 Na2EDTA adjusted to pH=9.0,exhibits an apparently super-Nernstian response(ΔE=180 mV) in the concentration range of 1×10-6 to 1×10-5 mol·L-1 Ca2+.In the super-Nernstian potential response range,the potential is linearly related to the total Ca2+ concentration,but not to free Ca2+ activity.This study provides a simple and effective method for speciation analysis.