Development of microfluidic analytical device for determination of heavy metals

Abstract

This research aimed to develop a microfluidic analytical device for determination of heavy metals, which can be divided into 3 parts. The first part is the development of microfluidic paper-based colorimetric device using thiosulfate catalytic etching of silver nanoplates for determination of copper. This device offers high sensitivity and selectivity for determination of copper over other metal ions. The color change can be monitored by the naked eye. The limit of detection was found to be 0.3 ng mL-1 and the relevant calibration curves was linear in the range of 0.5 - 200.0 ng mL-1 by ImageJ analysis. The second part is simultaneous determination of lead, cadmium and copper using microfluidic paper-based analytical device with dual electrochemical and colorimetric detection. Electrochemical detection was applied for determination of lead and cadmium using a bismuth film modified boron-doped diamond electrodes (Bi-BDDE). For the copper assay, the concentration of copper was measured by colorimetric detection based on the catalytic etching of silver nanoplates by thiosulfate. Under optimized conditions, the linear range obtained was found to be 0.5 - 70 ng mL-1 for lead and cadmium, 10 - 350 ng mL-1 for copper, and the detection limits were 0.1 ng mL-1 for lead and cadmium, and 5.0 ng mL-1 for copper. The final part is development of analytical method for the determination of heavy metal using a nafion/ionic liquid/graphene composite modified screen-printed carbon electrode. The composite-modified electrode was fabricated and evaluated for the highly sensitive simultaneous determination of zinc, cadmium and lead, which the detection limits of the simultaneous analyses were 0.09 ng mL-1, 0.06 ng mL-1 and 0.08 ng mL-1, respectively. This composite-modified electrode can be a candidate working electrode used in a microfluidic analytical device for determination of heavy metals in the future. Moreover, all proposed assays were applied to detect heavy metals in real samples (e.g. food, environmental and clinical samples), which the results were in good agreement with obtained from those of the standard methods.