Reverse Current Pulse Method To Restore Uniform Concentration Profiles in Ion-Selective Membranes. 1. Galvanostatic Pulse Methods with Decreased Cycle Time
Reverse Current Pulse Method To Restore Uniform Concentration Profiles in Ion-Selective Membranes. 1. Galvanostatic Pulse Methods with Decreased Cycle Time
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DOI：
10.1021/ac801984d
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发表时间：
2009-07-01
影响因子：
7.4
通讯作者：
Lindner, Erno
中科院分区：
文献类型：
--
作者：
Zook, Justin M.;Lindner, Erno
离子选择电极（ISEs）的应用通过引入恒流电流脉冲方法在电位分析中得到了扩展。在这些应用中，一个重要的要求是在每次测量之间恢复ISE膜的均匀平衡浓度分布。最简单的恢复方法是零电流松弛，即膜在开路条件下在扩散控制过程中松弛。本文提出了一种利用逆电流脉冲进行恢复的新方法。这种恢复方法的分析模型被导出来预测在恒流电流脉冲后ISE膜内的浓度分布。该模型允许计算薄膜电压松弛回零电流平衡值时的电压瞬态。用光谱电化学显微镜（SpECM）对预测的浓度分布和电压瞬态进行了验证。本文所描述的反向电流恢复方法与零电流恢复方法相比，电压漂移和电压误差减小了10-100倍。因此，这种新方法在大多数时间电位测量ISE应用中提供了更快和更可重复性的电压测量，例如提高检测限和确定膜物种的浓度和扩散系数。反向电流恢复方法的一个限制是，它不能用于一些应用，需要背景电解质负载膜没有过量的亲脂性阳离子交换剂。
The applications of ion-selective electrodes (ISEs) have been broadened through the introduction of galvanostatic current pulse methods in potentiometric analysis. An important requirement in these applications is the restoration of the uniform equilibrium concentration profiles in the ISE membrane between each measurement. The simplest restoration method is zero-current relaxation, in which the membrane relaxes under open-circuit conditions in a diffusion-controlled process. This paper presents a novel restoration method using a reverse current pulse. An analytic model for this restoration method is derived to predict the concentration profiles inside ISE membranes following galvanostatic current pulses. This model allows the calculation of the voltage transients as the membrane voltage relaxes back toward its zero-current equilibrium value. The predicted concentration profiles and voltage transients are confirmed using spectroelectrochemical microscopy (SpECM). The reverse current restoration method described in this paper reduces the voltage drift and voltage error by 10-100 times compared to the zero-current restoration method. Therefore, this new method provides faster and more reproducible voltage measurements in most chronopotentiometric ISE applications, such as improving the detection limit and determining concentrations and diffusion coefficients of membrane species. One limitation of the reverse current restoration method is that it cannot be used in a few applications that require background electrolyte loaded membranes without excess of lipophilic cation exchanger.