Spectroelectrochemical detection using thermal lens microscopy with a glass-substrate microelectrode-microchannel chip

We have developed spectroelectrochemical detection using thermal lens microscopy (EC-TLM) with a microelectrode-microchannel chip (EMC). TLM has both high sensitive and spatial resolution comparable to fluorometry, while it can be applied to non fluorescent analytes. EMC provides an efficient electrolysis of the analyte and a controlled distribution of the redox product in the microchannel. Therefore, a combination of TLM and EMC enhance both the sensitivity and selectivity. To show the performance of EC-TLM, we fabricated a glass substrate EMC and constructed the detection system. Experiments showed that the potential dependence of the EC-TLM signal of o-tolidine agreed very well with the current signal obtained simultaneously. The EC-TLM signal depended on the detection point in the microchannel and was compared with distribution profiles of the oxidized species predicted by computer simulation. Under the present experimental conditions, EC-TLM could detect of the order of 10−6 mol dm−3o-tolidine in μm-sized space with both signal-to-background and signal-to-noise ratios of 10. The results clearly showed that EC-TLM worked as expected and had adequate potential for use in sub-nano molar detection in micrometer-sized space.