Rotating electrode potentiometry: Lowering the detection limits of nonequilibrium polyion-sensitive membrane electrodes
Rotating electrode potentiometry: Lowering the detection limits of nonequilibrium polyion-sensitive membrane electrodes
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DOI：
10.1021/ac000756g
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发表时间：
2001-01-15
影响因子：
7.4
通讯作者：
Meyerhoff, ME
中科院分区：
文献类型：
--
作者：
Ye, QS;Meyerhoff, ME
旋转电极配置被评估为降低新设计的聚离子敏感膜电极（PSE）检测限的一种手段。平面电位聚阳离子和聚阴离子PSE通过分别将三十二烷基甲基氯化铵和二壬基萘磺酸钙掺入塑化PVC或聚氨酯膜中并将此类膜的盘安装在容纳于常规旋转盘电极装置中的电极体上来制备。 PSE 以 5000 rpm 的速度旋转，导致肝素（聚阴离子）和鱼精蛋白（聚阳离子）的检测限比使用搅拌棒评估相同电极的 EMF 响应以实现对流质量传输时观察到的结果提高至少 1 个数量级（肝素为 0.01 单位/mL；鱼精蛋白为 0.02 微克/mL）。观察到 omega (-1/2)（其中 omega 是旋转角频率）与 C-1/2（对应于对聚离子物质的总最大 Delta EMF 响应的一半的聚离子浓度）之间的线性关系。进一步表明，当用鱼精蛋白滴定低浓度肝素样品时，旋转聚阳离子传感器可以用作终点检测器，以大大提高（相对于非旋转指示电极）测量低浓度肝素的分析分辨率和精度。基于此类传感器独特的非平衡响应机制，讨论了通过旋转PSE降低检测限的理论依据。
A rotating electrode configuration is evaluated as a means to lower the detection limits of newly devised polyion-sensitive membrane electrodes (PSEs). Planar potentiometric polycation and polyanion PSEs are prepared by incorporating tridodecylmethylammonium chloride and calcium dinonylnaphthalenesulfonate, respectively, into plasticized PVC or polyurethane membranes and mounting disks of such films on an electrode body housed in a conventional rotating disk electrode apparatus. Rotation of the PSEs at 5000 rpm results in an enhancement in the detection limits toward heparin (polyanion) and protamine (polycation) of at least 1 order of magnitude (to 0.01 unit/mL for heparin; 0.02 mug/mL for protamine) over that observed when the EMF responses of the same electrodes are assessed using a stir-bar to achieve convective mass transport. A linear relationship between omega (-1/2), where omega is the rotating angular frequency, and C-1/2, the polyion concentration corresponding to half the total maximum Delta EMF response toward the polyion species, is observed. It is further shown that the rotating polycation sensor can be used as an end-point detector to greatly enhance (relative to nonrotated indicator electrode) the analytical resolution and precision for measurement of low concentrations of heparin when such samples are titrated with protamine. The theoretical basis for lowering the detection limits by rotating PSEs is discussed based on the unique nonequilibrium response mechanism of such sensors.