The Study And Application Of Microfluidic Electrochemical Sensor For Heavy Metal Ion

The on-chip electrochemical sensor is small and portable for on-site pollution detection,which is designed by integrating micro there-electrode with microfluidic chip.In addition,without the need of oxygen removal and complex pretreatment,heavy metal ions in a few microliters sample can be detected rapidly,sensitively and online in the on-chip electrochemical sensor.This paper focuses on the design and preparation of two kinds of on-chip electrochemical sensors for the detection of different heavy metal ions.It contains the following two parts:1.In this paper,an on-chip electrochemical sensor was designed by integrating an indium tin oxide(ITO)three-electrode with a low-volume cell,and trace Hg2+ was detected by differential pulse anodic stripping voltammetry(DPASV)after online flow accumulation in the sensor.The working electrode of the ITO three-electrode was composed of in-situ electrodeposited flower-cluster AuNPs microarray on the surface of the ITO,the reference electrode was Ag/AgCl,and the auxiliary electrode was ITO.The low-volume cell consisted of an ITO slide and a coverslip to form a ridge-rectangular chamber with a depth of 400 μm and a volume of 28.8 μL.The in-situ flow accumulation in the on-chip electrochemical sensor was used to detect the linear range of Hg2+ from 0.63 to 80 ppb with a detection limit of 0.11 ppb(S/N=3).The sensors had good selectivity towards Hg2+ in the interferences of eight common cations.The recovery rates of 1 ppb Hg2+ were 101%in the tap water and 106%in the lake water.Compared with the traditional detection method,the on-chip electrochemical sensor by the in-situ flow accumulation of Hg2+ required low-volume sample and got a more sensitive and stable signal,so it had the excellent potential for on-site and real-time detection of mercuric pollutant.2.In this work,a thin-layer electrochemical flow cell was prepared by integrating a screen-printed carbon electrode(SPCE)with a microfluidic chip.After on-line flow preconcentration by in-situ electrodeposition of bismuth film on the SPCE,Cd2+ was detected by square wave anodic stripping voltammetry(SWASV).Without any modification treatment on the SPCE and oxygen removal in the sample,we could process the entire detection automatically and get test results just by one-step.After the optimization in the concentration of Billachannel liquid velocity,preconcentration voltage and time,the thin-layer electrochemical flow cell was used to detect the linear range of Cd2+from 1 ppb to 80 ppb with a detection limit of 0.88 ppb(S/N=3).The same thin-layer electrochemical flow cell could be continuously used for more than 50 times,also good detection reproducibility could be got among different electrochemical flow cells.The recovery rate of Cd2+ obtained in tap water by standard sample addition method was 97%-107.5%.The thin-layer electrochemical flow cell based on SPCE has the advantages of lower consumption of sample and reagents(≤1.5mL),low cost and high degree of automation,which can be used for on-line and on-site detection of trace heavy metal ions.