A multichannel closed bipolar platform to visual electrochemiluminescence sensing of caffeic acid as a model:...

In this study, a fully-featured electrochemiluminescence (ECL) sensing platform based on a multichannel closed bipolar system (closed-BP, C-BP) for the determination of caffeic acid (CA) was successfully developed. The system comprises three individual reservoirs connected to each other by two pairs of gold rods as bipolar electrodes. Moreover, a single pair of gold rods functions as the driving electrodes. Due to configuration consisting of three channels and double-bipolar electrodes, the detection of CA was accomplished in two oxidation and reduction pathways within a single device. Firstly, through close observation of the reactions occurring within the device and utilizing a universal pH indicator and bipolar electrodes, a precise mechanism for the current bipolar systems was initially proposed. Then, the concentration of CA was monitored in the reporting chamber through the following ECL intensities resulting from luminol oxidation and H₂O₂. The monitoring process was performed using both a photomultiplier tube (PMT) and a digital camera. In the process of analyte oxidation, the PMT and visual (camera)-based detection exhibited a linear response from 5 μmol L^-1 to 700 μmol L^-1 (limit of detection (LOD) 1.2 μmol L^-1) and 50 μmol L^-1 to 600 μmol L^-1 (LOD 14.8 μmol L^-1), respectively. In the analyte reduction pathway, the respective values were 30 μmol L^-1 to 450 μmol L^-1 (LOD 8.6 μmol L^-1) and 55 μmol L^-1 to 400 μmol L^-1 (LOD 21.2 μmol L^-1), for the PMT and visual-based detection, respectively. Our experiments have demonstrated the practical application of the sensor array for efficient and high-performance analysis. This innovative design holds significant potential for diverse fields and paves the way for the development of a user-friendly device.