Departamento de Tecnologia e Ciência Dos Alimentos, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil; Departamento de Química, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil.
Instituto de Ciência e Tecnologia Dos Alimentos, Universidade Federal Do Rio Grande Do Sul, 91501-970, Porto Alegre, RS, Brazil.
Talanta. 2020 Aug 15;216:120975. doi: 10.1016/j.talanta.2020.120975. Epub 2020 Apr 5.
This work proposes a simple device for thermometric titration using a contactless sensor. A low-cost infrared sensor (around $5) was adapted in a disposable, polystyrene vessel for monitoring the temperature to determine the endpoint of neutralization, redox, and complexation titrations, using a homemade syringe pump to titration control. Open-source software was developed to control the device using the Raspberry Pi platform and to perform automatic endpoint determination. The influence of sample volume, the flow rate of titrant, and sensor distance from the solution were evaluated to lower the variation among measurements. The parameters chosen in this regard were 10 mL of sample, 0.8 mL min of titrant solution flow rate, and 3 cm of distance from the sensor to the solution. Results for the determination of the acidity of sauces and the ascorbic acid and calcium content of pharmaceutical products were compared with those from official compendia. The performance of the sensor also was compared with an infrared camera. The proposed method agreed with conventional ones to an extent ranging from 93% to 106%. The robust analytical performance and low cost of the system are essential features that could broaden the use of enthalpimetric analysis in several laboratories.
本工作提出了一种使用非接触式传感器进行量热滴定的简单装置。一个低成本的红外传感器（约 5 美元）被改装在一次性聚苯乙烯容器中，用于监测温度以确定中和、氧化还原和络合滴定的终点，使用自制的注射器泵进行滴定控制。开发了开源软件来控制使用 Raspberry Pi 平台的设备，并进行自动终点确定。评估了样品体积、滴定剂流速以及传感器与溶液之间的距离等因素对降低测量差异的影响。在这方面选择的参数是 10 mL 的样品、0.8 mL min 的滴定剂溶液流速以及传感器到溶液的距离为 3 cm。对酱汁酸度以及药物产品中抗坏血酸和钙含量的测定结果与官方药典进行了比较。还将传感器的性能与红外摄像机进行了比较。所提出的方法与传统方法在 93%到 106%的范围内一致。该系统具有强大的分析性能和低成本，这是在多个实验室中拓宽量热分析应用的重要特征。
