Laminar Flow\nInfrared Spectroelectrochemistry

In this work, we advance lab-on-chip electrochemistry\nand spectroscopy\nby combining these capabilities onto a single platform, thereby achieving\nmid-infrared spectroelectrochemistry (SEC) for the first time. The\nkey feature of this technique is the use of deterministic laminar\nflow patterns to precisely transport a reacted solution from upstream\nelectrodes to a downstream spectral detection region. Laminar flow\nspectroelectrochemistry (LF-SEC) is therefore a completely new approach,\nwhich derives its distinction and advantage over traditional SEC by\nphysically separating electrode and attenuated total reflection (ATR)\nelements. As such, these functional elements retain optimal properties,\nsuch as inert, highly conductive electrodes and a bare ATR element\nfor sensitive Fourier transform infrared (FTIR) spectroscopy. By combining\nATR-FTIR with a scanning aperture system, LF-SEC provides the additional\nadvantage of spectroscopically monitoring reactions at individual\nelectrodes. The LF-SEC system design is first optimized through a\nseries of targeted experiments using a ferricyanide/ferrocyanide redox\npair to validate electrochemical functionality, undertake spectroscopic\ncalibration, optimize experimental parameters, and finally validate\nthe quantitative relationship between FTIR results and the reaction\nrate under galvanostatic control. After optimization, we demonstrate\nthe technique by monitoring the oxidation of the therapeutic compound\nascorbic acid (vitamin C) in the presence of biomolecular interference\nfrom a molecule with an overlapping oxidation potential. We find that\nmolecular availability causes the reaction to switch between reaction\npathways, which we could finely monitor using LF-SEC. This work opens\nthe door to future developments that take advantage of the microfluidic\nreactor setup, with benefits ranging from portability to high-throughput\nstudies under precise reaction conditions.