Rapid acquisition of absorption spectra to monitor proton migration in nanoliter space using the RGB-spectrum-conversion method with a 10 ms interval.

Acquisition protocol of absorption spectra at nanoliter spaces from the RGB values preserved in video data at 10 ms intervals was established using the principal-component-analysis-based RGB-conversion method. Proton behavior was monitored using a camera to acquire the video footage to monitor colorimetric change in the nanoliter space. The RGB values observed in the video were converted into a score vector using a conversion matrix. A linear combination of the predetermined loading vectors with the score values was calculated to reproduce the absorption spectra. The reproduced absorption spectra correlated well with those acquired using a conventional spectrophotometer during a short period. This method was applied to monitor the proton diffusion from a single cationic ion-exchange resin into hydrogels at low concentrations. The rapid acquisition and quick response of this method may enable the monitoring of the initial diffusion of protons, which is challenging with conventional spectrophotometry and electrochemical approaches.