Development of Zinc Ion Sensor for Monitoring of Surface Coating Processes and its Use in Practical Electroplating Solutions

研制了锌（II）电位传感器的两种变体，用于监测电镀液中锌的浓度。它们都是基于膜涂层碳棒电极，但在膜的传感成分的性质上有所不同。一种含有离子交换型，即双[二（2-乙基己基）二硫代磷酸锌](ZnDTP)，而另一种含有中性离子载体，即四异丁基硫代二硫化（TiBTDS）作为传感材料。两种传感器在较宽的浓度范围内对锌水溶液的检测均有良好的响应。ZnDTP传感器的检测限为6*10^<-6> M，工作pH范围为4.0-7.0。在工作pH 1.8 ~ 7.2范围内，TiBTDS电极的检出限为5 × 10^<-7> M。利用该电极获得的电位选择系数数据证明，基于离子载体的传感器对除Cu、Pb和Cd以外的大多数常见金属的锌的测定具有很高的选择性。另一方面，离子交换型传感器对其他干扰物的选择性较差。Cu、Pb和Cd对Zn (II)-TiBTDS传感器不可避免的干扰被认为是由于配体分子中存在软硫供体而产生的。将TiBTDS液膜与表面等离子体共振（SPR） Zn （II）传感器结合作为识别元件，获得了不同的锌选择性模式。这表明利用TiBTDS可以实现一个可靠的锌传感器。作为Zn-TiBTDS的实际应用，对电镀液中锌浓度的变化进行了5小时的监测。观测值与原子吸收光谱法测定值吻合较好。实验结果表明，TiBTDS是一种检测水中锌离子的良好传感材料。

Two variations of potentiometric sensors for Zn (II) were developed for monitoring of zinc concentration in electroplating bath solutions. They are based on membrane-coated-carbon rod electrodes but differ in the nature of the sensing component of the membrane. One contains an ion exchange type, viz. Zinc Bis [di (2-ethylhexyl) dithiophosphate] (ZnDTP) while the other incorporates a neutral ionophore i.e. tetra-isobutyl thiuram disulfide (TiBTDS) as the sensing material. Both the sensors showed good response to the detection of aqueous zinc (II) over a wide range of concentration. The ZnDTP sensor provided a detection limit of 6*10^<-6> M with the working pH range of 4.0-7.0. The detection limit for the TiBTDS electrode was 5*10^<-7> M in the operational pH of 1.8-7.2. Potentiometric selectivity coefficient data obtained with the present electrodes proves that the ionophore based sensor possesses high selectivity for determination of zinc over most of the commonly encountered metals except Cu, Pb and Cd. The ion exchange type sensor, on the other hand, is characterized by having poor selectivity against other interferants. The rather unavoidable interference of Cu, Pb, and Cd on the Zn (II)-TiBTDS sensor is thought to arise because of the presence of soft sulfur donors in the ligand molecule. When the liquid membrane of the TiBTDS was incorporated in a surface plasmon resonance (SPR) Zn (II) sensor as the recognition element, a different selectivity pattern was obtained for the determination of zinc. This indicates that a reliable zinc sensor could be realized using TiBTDS.As a practical application of the Zn-TiBTDS, the change in zinc concentration in an electroplating solution was monitored for five hours. The observed concentration values agreed well with the values measured by AAS.It can be concluded that TiBTDS forms a good sensing material for detection of zinc ions in aqueous media.