Coulometric detection of an analyte in a liquid plug formed in a microflow channel

Applicability of coulometric detection was tested for the analysis of an analyte in a liquid plug confined in a PDMS microflow channel. A plug prepared in the flow channel was placed on a three-electrode system and hydrogen peroxide was detected. With plugs of a small volume, the depletion of the analyte was rapid, making reproducible amperometric detection difficult particularly when the flow channel was shallow. On the other hand, coulometric detection showed a clear relationship between the generated charge and the concentration. However, when the volume of the plug was large, only a part of the analyte was used for detection, suggesting the possibility to improve the detection sensitivity further. The device was also tested in the detection of L-glutamate.