Application Of Graphene Nanomaterials In Rapid Analysis Of Food Safety And Quality

There has been an increase in reports on food safety in the past few years,and the demands for the grasp of food safety in daily life has got an unprecedented attention.Traditional food analysis methods have the merits of high sensitivity,but they also suffer from high cost and time consuming.Compared with these traditional methods,electrochemical sensors are proved due to their advantages of low-cost,less time consuming and simple method of operation.They can also be highly sensitivity,accuracy and so on.However,traditional electrodes suffer from poor stability and reproducibility,which are the limit of its wider application.Utilizing the knowledge of electrochemical detection technology and nanotechnology,a gold nanoparticles and graphene nanomaterial modified glassy carbon electrode was developed for the determination of nitrite and heavy metal ions in food and water,and the levels of antioxidant epigallocatechin gallate(EGCG)was also analyzed with this electrode.Besides,a graphene-based freestanding flexible paper-like electrode was developed by vacuum filtration method for Pb2+determination in this paper,mainly including the following:1)A simple one-step in-situ synthesis method of gold nanoparticles and graphene modified glassy carbon electrode(AuNPs/GR/GCE)was studied in this part for the detection of nitrite ions in pickled food.Under the optimum conditions,the DPV results demonstrated that the electrode had a good linear relationship between peak current and nitrite concentration ranging from 0.4 μM to 2400μM with a limit of detection(LOD)of 0.098 μM(R2=0.997).Furthermore,the modified electrode was successfully applied to the determination of nitrite in the pickled food and had a good recovery in the range of 93.7%to 104.43%.2)In this part,an environmentally friendly method was established for the determination of Pb2+based on the AuNPs/GR/GCE without Hg or Bi ions.The analytical performances of electrochemical sensor are as follows:(1)Under all optimization conditions,the linear range for Pb2+ is 1-90 μg/L with the LOD of 0.27 μg/L(R2=0.985)(S/N=3);(2)The electrode is successfully applied for the analysis of Pb2+ in water and soil samples and the recovery ranges are 98.70%～102.73%and 93.82%-109.92%.with all RSDs are below 7%.3)The electrocatalytic oxidation of(-)-epigallocatechin gallate is investigated with AuNPs/GR/GCE in this part.Under the optimum conditions.DPVs are recorded and the peak current increased linearly with the concentration of EGCG changed from 0.5 to 40 μmol/L with a LOD of 0.162 μmol/L.Meanwhile,the electrode has the ability to accurately distinguish(-)-epigallocatechin(EGC),(+)-Catechin(C)and EGCG by different peak potentials.Finally,the electrode is successfully applied to the analysis of levels of EGCG in green tea infusing samples.4)A graphene-based freestanding flexible paper-like electrode(rGOP electrode)with double reduction processes is developed for the determination of Pb2+ in water.Compared with the AuNPs/GR/GCE mentioned above,the rGOP electrode has a lower deposition potential and long deposition time with no hydrogen evolution.Under the optimum conditions,the linear range for Pb2+is 5-55 μg/L with the LOD of 1.6 μg/L,and the results are basically free from interference from other metal ions.