Design And Characterization Of An Embedded Amperometric Analyzer For Field-Portable Electrochemical Applications

A novel miniaturized amperometric analyzer with enhanced performance was developed to meet the need of field-portable, wide adaptable, user friendly, and cost effective electrochemical detection in various application fields. Based on the new MSP430FG479 microcontroller, the embedded system was designed to either operate as a stand-alone unit with an on-board fool-proof user interface, or run on the user’s PC for advanced data analysis. Amperometric detection is a powerful experimental approach for the study of electro-active compounds with clinical, industrial, environmental and agricultural importance. Inside the amperometric analyzer, a mini-potentiostat is designed to interface with a wide spectrum of electrochemical sensors. Implemented with grounded-auxillary electrode configuration, the mini-potentiostat controls oxidationreduction reactions of target analytes at the working electrode surface by accurately maintaining a preset potential between the working (WE) and the reference electrode (RE), while measuring the redox current response at the auxillary electrode (AE) using a low-side resistive sensing mechanism. In an unstirred solution, at steady state, the rate of electron transfer is directly proportional to the concentration of the reactant. Therefore, the steady state current is used as an accurate measure of the analyte concentration in the sample. Constructed using off-the-shelf IC chips and powered by a single 3V lithium coin cell battery, the potentiostat circuitry inside the amperometric analyzer is designed to meet potential control and current detection requirements for most existing electrochemical sensors. Featured with sub-picoampere sensitive, wide span and high accuracy current sensing, the specially designed current sensing block not only covers general application requirements, but it can also serve as a powerful tool in research efforts toward the next generation of ultra-sensitive detection systems in biomolecular sensing. In addition to the superior electrochemical related specifications, various lowpower design techniques have been applied to ensure a prolonged battery life, therefore making the system an ideal platform for amperometric monitoring in field appropriate applications. Confirmed with a systematic evaluation of the device prototype, the system features a 4-month battery life with a single 3V lithium battery (220mAh), accurate bidirectional redox potential control from -1.2V to +1.2V, high resolution current detection from ±5pA to ±1mA covered by 4 software selectable detection levels, improved stability unaffected by electrochemical sensor impedance, and high EMI immunity without external shielding. Finally, electrochemical analyses were also conducted using the device prototype. For a constant potential amperometric experiment, the experimental results of the system were compared with a standard bench top electrochemical workstation (the BAS Epsilon). Excellent agreement was attained over the whole detection range, which demonstrates the excellent potential control and current sensing abilities of the amperometric analyzer.