Borges Sivanildo S, Vieira Gláucia P, Reis Boaventura F
Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Avenida Centenário 303, 13400-970 Piracicaba, SP, Brazil.
J Autom Methods Manag Chem. 2007;2007:46219. doi: 10.1155/2007/46219.
In this work, an automatic device to deliver titrant solution into a titration chamber with the ability to determine the dispensed volume of solution, with good precision independent of both elapsed time and flow rate, is proposed. A glass tube maintained at the vertical position was employed as a container for the titrant solution. Electronic devices were coupled to the glass tube in order to control its filling with titrant solution, as well as the stepwise solution delivering into the titration chamber. The detection of the titration end point was performed employing a photometer designed using a green LED (lambda=545 nm) and a phototransistor. The titration flow system comprised three-way solenoid valves, which were assembled to allow that the steps comprising the solution container loading and the titration run were carried out automatically. The device for the solution volume determination was designed employing an infrared LED (lambda=930 nm) and a photodiode. When solution volume delivered from proposed device was within the range of 5 to 105 mul, a linear relationship (R = 0.999) between the delivered volumes and the generated potential difference was achieved. The usefulness of the proposed device was proved performing photometric titration of hydrochloric acid solution with a standardized sodium hydroxide solution and using phenolphthalein as an external indicator. The achieved results presented relative standard deviation of 1.5%.
在这项工作中，提出了一种自动装置，该装置能够将滴定剂溶液输送到滴定室中，并能确定所输送溶液的体积，其精度良好，与经过的时间和流速均无关。一根保持垂直位置的玻璃管被用作滴定剂溶液的容器。电子设备与玻璃管相连，以控制其用滴定剂溶液填充，以及将溶液逐步输送到滴定室中。滴定终点的检测是使用一个由绿色发光二极管（波长=545纳米）和一个光电晶体管设计的光度计来进行的。滴定流动系统包括三通电磁阀，这些电磁阀被组装起来，以使包括溶液容器装载和滴定运行的步骤能够自动进行。用于确定溶液体积的装置是使用一个红外发光二极管（波长=930纳米）和一个光电二极管设计的。当从所提出的装置输送的溶液体积在5至105微升范围内时，所输送的体积与产生的电位差之间实现了线性关系（R = 0.999）。通过用标准氢氧化钠溶液对盐酸溶液进行光度滴定并使用酚酞作为外部指示剂，证明了所提出装置的实用性。所获得的结果呈现出1.5%的相对标准偏差。
