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Introduction

For the electrochemical detection system to achieve it's full potential, various conditions needed to be optimized for our purposes. These included the buffer solution present and the type of electrode plating used. The final conditions will be incorporated into the field-ready kit that can be used by anyone with minimal training.

Buffer solutions

We tested over 11 potential buffering systems to find the optimal graph for chlorophenol red detection. The hallmark of a good buffer is one that can conduct a current effectively and has no species present that will undergo a redox reaction at the voltage you are measuring. For our project, we were looking at an oxidation reaction at -0.7V on our detection system. A good buffer for us will have a consistent flat line between -1V and -0.5V. Another feature of a good buffer is that the difference between the cathodic and anodic sweeps is not large. This is easy to notice, as the larger the difference, the bigger the gap between upper and lower lines during the flat section around 0V. The results of our buffer screens are shown in Figure 1.

Based on the results show above, 0.1M CaCl₂ was the best buffering system, as it had consistently flat areas through the testing range and conducted large currents. It was also shown that acetonitrile at 0.01% was the worst solvent, and it cause massive electrode degradation during the test runs.

Plating methods

When electrodes are plated with certain metals they can perform redox reactions that can improve the resolution of the reading obtained. One example of this is silver/silver chloride electrodes. When a voltage is applied to Ag/AgCl electrodes, the silver that is bound to the chloride can become silver metal and release electrons. This is an important reaction, as the reference electrode used in our detection system is an Ag/AgCl electrode.

To test various plating methods, we chose common plating metals and tested them all in the same buffer solution. The metal that gave the best resolution and consistency would be the best metal to plate our electrodes with. Plating was achieved by applying a voltage of 1V to the solution and stirring to draw the metal ions to the desired electrode.