Embedded mini-analyzer device for in situ wide range heavy metal identification and concentration detection

Metal toxicity is a critical concern in both human health and ecosystem. Many heavy metals are lethal at high concentration. It can also be harmful at trace concentration since accumulating such materials in human organs lead to longterm negative health effects such as cancer, heart disease and high blood pressure. Therefore, heavy metal detection of trace concentration is very important. Heavy metals can be detected using electrochemical detection system. It consists of electrodes, potentiostat that controls the electrode and signal processing block. With the advancement of integrated technology, in-situ electrochemical systems provide feasible solution for sensitive detection and miniaturized platform. The potentiostat as main part of the system; read, amplify and control the current flow through the electrodes. In this study, the fully differential variable gain potentiostat, would be able to measure wide range current of different types of electro chemicals, typically from 100 nA to 100 mA and can generate an excitation potential between -3V and +3V. This potentiostat is designed with a fully differential operational amplifier and rail-to-rail common-mode range buffer for linearity of output signal. Voltammetry as electrochemical technique is used in this project for the heavy metals detection. This designed device was able to perform differential pulse anodic stripping voltammetry (DPASV) as a sub techniques of voltammetry. Among many types of voltammetry techniques, differential pulse anodic stripping voltammetry (DPASV) technique was chosen where a pulse shaped voltage is applied on the sen- sor and the current through the sensor is measured to determine the concentration and types of heavy metal. To achieve the ability of in-situ processing of detection, embedded algorithms like digital FIR filter, multiple peaks finding, peaks classification and linear regressions have been implemented on an ARM processor. The resulted signals known as voltammogram and the concentration value will be displayed on a graphical LCD. Voltammogram is a plot of current reaction with applied voltage. Tests were carried out for solution with different heavy metals like cadmium (Cd), lead (Pb) and copper (Cu). A concentration range from 0.5 ppm to 10 ppm of lead have been used to test the system accuracy and detection limits. The system was able to detect the heavy metal with correlation factor of 0.99, between the concentration value and voltammogram current peaks.

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