Stainless steel sheets as the substrate of disposable electrochemical sensors for analysis of heavy metals or biomolecules.

In this paper, low-cost stainless steel sheets with excellent electric conductivity were utilized as the robust substrate for fabrication of disposable working electrodes. The stainless steel electrodes were modified with carbon cement and then coupled in paper-based analytical devices for analysis of heavy metals (cadmium and lead) in toys or indole-3-acetic acid (IAA) in plants, respectively. For stripping analysis of cadmium and lead, the dilution ratio of the carbon cement, the pH value of the buffer solution, the pre-deposition potential and time, and the bismuth concentration were optimized with the detection limits reaching 1 μg•L-1. After optimization of the dilution ratio of carbon cement, the similar devices could also be used for analysis of IAA at the concentration of less than 0.5 μM. This strategy could be successfully applied for differentiation of migratable lead in toys or in situ amounts of IAA in root tips of Arabidopsis thaliana in real time, respectively. Our results implied that the electric conductivity of the substrate could possibly be critical for the improvement of the analytical performance of the modified electrodes. This study suggested that stainless steel could become a suitable and cost-effective substrate for fabrication of disposable carbon-based electrodes used in electrochemical detection.