An integrated microfluidic device with solid-phase extraction and graphene oxide quantum dot array for highly sensitive and multiplex detection of trace metal ions.

An integrated microfluidic device, consisting of a solid-phase extraction (SPE) unit for metal ion pretreatment, a micropump, a micromixer, and a detachable graphene oxide quantum dot (GOQD) array chip was constructed for selective and sensitive detection of As3+, Cd2+, and Pb2+. The entire process could be sequentially and automatically completed by actuating a pneumatic micropump. Effect of the pH for metal ion capture and pumping scheme for recovery efficiency were investigated on a chip. The ion As3+, Cd2+, and Pb2+ whose concentrations ranged from 10-2 µM to 102 µM were successfully recovered with high efficiency over 80%. Monoplex and multiplex detection of As3+, Cd2+, and Pb2+ were then executed on a GOQD array chip. The target metal ions were specifically captured on the DNA aptamer linked GOQD array, which results in the fluorescence quenching of GOQD due to the electron transfer from the GOQD to metal ions under the laser irradiation. The proposed integrated SPE-GOQD array based microdevice could perform As3+, Cd2+, and Pb2+ detection with detection limits of 5.03 nM, 41.1 nM, and 4.44 nM, respectively. Simultaneous multiplex detection for binary or ternary mixture of As3+, Cd2+, and Pb2+ was performed, and the proposed integrated microdevice also showed high recovery values ranging from 83.52% to 128.3% from the environmental samples.