Circuit to control the reference and counter electrodes.

<p>One of two DACs can be used to control the voltage, based on if the external capacitor is installed. An Opamp buffers the DAC voltage and an analog multiplexer is used to select if 2 or 3 electrode experiments should be performed.</p

Comparison to a commercial potentiostat using standard electrodes.

<p>A) Raw current traces of cyclic voltammetry experiments in 5 mM ferricyanide using an EmStat (black) and PSoC-Stat (blue) with the voltage in reference to a Ag /AgCl reference electrode. B) Currents from A with the noise removed using a 10 point rolling sample.</p

PSoC-Stat: A single chip open source potentiostat based on a Programmable System on a Chip

<div><p>In this paper we demonstrate a potentiostat built with a single commercially available integrated circuit (IC) that does not require any external electronic components to perform electrochemical experiments. This is done using the capabilities of the Programmable System on a Chip (PSoC^®) by Cypress Semiconductor, which integrates all of the necessary electrical components. This is in contrast to other recent papers that have developed potentiostats but require technical skills or specialized equipment to produce. This eliminates the process of having to make a printed circuit board and soldering on electronic components. To control the device, a graphical user interface (GUI) was developed in the python programming language. Python is open source, with a style that makes it easy to read and write programs, making it an ideal choice for open source projects. As the developed device is open source and based on a PSoC, modification to implement other electrochemical techniques is straightforward and only requires modest programming skills, but no expensive equipment or difficult techniques. The potentiostat developed here adds to the growing amount of open source laboratory equipment. To demonstrate the PSoC potentiostat in a wide range of applications, we performed cyclic voltammetry (to measure vitamin C concentration in orange juice), amperometry (to measure glucose with a glucose strip), and stripping voltammetry experiments (to measure lead in water). The device was able to perform all experiments and could accurately measure Vitamin C, glucose, and lead.</p></div

Amperometric experiments.

<p>A) Current traces measure at +500 mV using Accu-Check Performa glucose strips. 3 strips were used for each glucose sample. B) Average current between 4.8 and 5 seconds of the amperometric currents is plotted versus the glucose in the samples. Our device measured a linear relationship (R² = 0.98) over the physiological range of glucose within the range of the FDA’s guidelines.</p

Cyclic voltammetry experiments.

<p>A) Raw current traces of cyclic voltammetry experiments in orange juice with different levels of added ascorbate. Voltage is in reference to a Ag /AgCl reference electrode. B) Standard addition results of the cyclic voltammetry experiments. The current value at +550 mV was used and a fitted line to the data was used to calculate the amount of ascorbate in the orange juice.</p

Current measuring circuit.

<p>A transimpedance amplifier (TIA) and a DAC are used to set the voltage and measure the current passing through the working electrode. The TIA output voltage is passed into a delta sigma ADC, which converts the analog signal into a digital signal. A current DAC is used to calibrate the TIA / ADC signal chain. If an increase in the maximum current is needed, pins are made available that external resistors can be connected to.</p

Anodic Stripping Electrode experiments.

<p>A) Raw current traces of the stripping step with added Pb²⁺. Voltage is in reference to a Ag /AgCl reference. electrode. B) Raw traces normalized to the -350 mV current level. C) Current with the average baseline subtracted from all traces. D) Relationship of the current at -175 mV of the baseline subtracted traces versus the Pb²⁺ concentration.</p

Screenshot of GUI to control the potentiostat.

<p>Different electrochemical techniques use different tabs in the main GUI. Important information for each experiment type is displayed to the user and a pop-up interface allows the user to change each parameter. The voltage source and electrode configuration settings are displayed to the user.</p

Comparison of different potentiostats.

<p>Comparison of different potentiostats.</p

Potentiostat parts and completed device.

<p>A) Photo of all the components needed to develop a single chip potentiostat and perform the experiments in this paper. <i>From the top</i>: EZ-Hook electrical connectors used to connect the device to glucose strips; CY8CKIT-059 that has the PSoC 5LP that contains all the electrical components needed for a potentiostat; headers that can be connected to the board, with either solder or conductive glue (Conductive glue is not as strong over time but requires less equipment and skill to use); The DVDAC capacitor is optional but will increase the resolution of the potentiostat; 3 alligator clips with female jumper cables ends to attach electrodes to the device; a pencil lead electrode attached to a jumper wire with electrical glue. B) Photo of the assembled device with a case. C) Device assembled in its case. D) Close up of the CY8CKIT-059 with labels for where the electrodes, capacitor and USB connections should be attached.</p