Simultaneous Determination Of Cd²⁺ And Pb²⁺ Based On Graphene/L-cysteine/Bi Modified Electrodes

Heavy metal irons such as Cd²⁺ and Pb²⁺ are discharged along with emission of industrial wastewater,which may cause great pollution to environment and threaten human health.So it is of great importance to quantitatively detect the heavy metal irons in water.Compared with other detection methods of heavy metal irons,electrochemical method has the advantages of high sensitivity,excellent selectivity,low cost and easy operation.Glassy carbon electrodes were modified with graphene/L-cysteine/Bi?GR/L-cys/Bi/GCE?via casting method and electrostatic adsorption method.Optimum condition was obtained by studying four main influence factors.Under the optimum condition,GR/L-cys/Bi/GCE was successfully applied in the separated detection and simultaneous detection of Cd²⁺ and Pb²⁺.The results show linear relation of oxidation peak current with Cd²⁺concentration in the range between 0.5?g/L and 110 ?g/L,with the detection limits of 0.90 ?g/L.Similarly,the oxidation peak current was proportianal to Pb²⁺concentration in the range between 10 ?g/L and 80 ?g/L,with the detection limit of 0.96 ?g/L.The peak positions of cadmium ions and lead ions on the GR/L-cys/Bi/GCE can be separated clearly.The detection ranges of cadmium and lead ions were from 10 ?g/L to 70 ?g/L and from 10 ?g/L to120 ?g/L,respectively.With the increase of ion concentration,the corresponding oxidation peak current increased linearly.GCE modified with GR/L-cys/Bi was successfully applied to detect Cd²⁺and Pb²⁺,which shows potential to detect Cd²⁺and Pb²⁺ with GR/L-cys/Bi.In addition,screen-printing electrode?SPE?was modified with GR/L-cys/Bi/GCE via casting method and electrostatic adsorption method.Under the optimum condition,GR/L-cys/Bi/SPE was successfully applied in the separated detection and simultaneous detection of Cd²⁺ and Pb²⁺.The results show linear relation of oxidation peak current with Cd²⁺concentration in the range between 5?g/L and 100 ?g/L,with the detection limits of 3.32 ?g/L.Similarly,the oxidation peak current was proportianal to Pb²⁺concentration in the range between 10 ?g/L and 90 ?g/L,with the detection limit of 0.51 ?g/L.The GR/L-cys/Bi/SPE can be used as a sensor for simultaneous detection of Cd²⁺and Pb²⁺,the oxidation peakcurrent of Cd²⁺and Pb²⁺increased in proportion to concentration in the range from10 ?g/L to 50 ?g/L.Stability,repeatability and selectivity were investigated and the analytical applicability of the modified electrodes was evaluated.GR/L-cys/Bi modified electrodes show good stability,high selectivity,repeatability,wide detection window and low detection limit,which makes it hold huge potential to serve in the Cd²⁺ and Pb²⁺ detection.