Yamada Akira, Suzuki Miho
Department of Mechanical Engineering, Graduate School of Engineering, Aichi Institute of Technology, Toyota 470-0392, Japan.
Sensors (Basel). 2017 Jul 4;17(7):1563. doi: 10.3390/s17071563.
The pH values of aqueous solutions are conventionally measured with pH-sensitive electrodes such as glass electrodes or ion-sensitive field-effect transistors (ISFETs) used in conjunction with Ag/AgCl reference electrodes and KCl solutions. The speed of pH measurement with these systems can be deficient, however, as the glass electrode responds slowly during measurements of sample solutions with low buffering capacities. Our group has constructed a new pH measurement system using a microfluidic device and ISFET sensors. The device has a channel with two inlets and one outlet, with a junction connected to a Y-shaped channel on the same plane. Two ISFET sensors and an Ag/AgCl pseudo reference electrode are fitted into the channel to construct a differential measurement device. A sample solution and baseline solution supplied into the inlets by gravity-driven pumps form a flowing liquid junction during measurement. The small size and fast response of the ISFET sensors enable measurement of about 2.0 mL of sample solution over a measurement period of 120 s. The 90% response time is within 2 s. The calibrated sensor signal exhibits a wide range (pH 1.68-10.0) of linearity with a correlation factor of 0.9997. The measurement error for all solutions tested, including diluted solutions, was 0.0343 ± 0.0974 pH (average error ± standard deviation (S.D.), n = 42). The new device developed in this research will serve as an innovative technology in the field of potentiometry.
水溶液的pH值通常使用pH敏感电极进行测量，如玻璃电极或与Ag/AgCl参比电极及KCl溶液配合使用的离子敏感场效应晶体管（ISFET）。然而，使用这些系统进行pH测量的速度可能较慢，因为在测量缓冲容量低的样品溶液时，玻璃电极响应缓慢。我们团队构建了一种使用微流控装置和ISFET传感器的新型pH测量系统。该装置有一个带有两个入口和一个出口的通道，在同一平面上有一个连接到Y形通道的连接点。两个ISFET传感器和一个Ag/AgCl伪参比电极安装在通道中，以构建一个差分测量装置。在测量过程中，由重力驱动泵供应到入口的样品溶液和基线溶液形成一个流动的液体连接点。ISFET传感器的小尺寸和快速响应使得在120 s的测量周期内能够测量约2.0 mL的样品溶液。90%的响应时间在2 s以内。校准后的传感器信号在很宽的范围（pH 1.68 - 10.0）内呈线性，相关系数为0.9997。包括稀释溶液在内的所有测试溶液的测量误差为0.0343 ± 0.0974 pH（平均误差±标准偏差（S.D.），n = 42）。本研究中开发的新装置将成为电位测定领域的一项创新技术。
