Screening Of Highly Sensitive Modified Electrodes And Their Application In The Detection Of Antibiotics In Cultured Seawater

Electrochemical analysis methods are well suited for the rapid detection of trace organic pollutants because of their high sensitivity,low cost and portability.In recent years,the overuse of antibiotics has exacerbated offshore pollution,and the residual antibiotics in seawater can damage the marine ecological balance on the one hand,and on the other hand,they can be enriched in organisms through the food chain,threatening the safety of aquaculture production and human health.To ensure the green development of aquaculture industry,the development of rapid detection technology for antibiotic residues in cultured seawater is a current research hotspot.Compared with freshwater environment,seawater composition is more complex,there are strong impurity interference,conventional chromatographic method is difficult to meet the field detection needs,and the application of traditional electrochemical sensors in the detection of seawater samples is limited,strengthen the study of electrode modification process,screening suitable modified electrodes to achieve the detection of trace antibiotics in cultured seawater,is of great significance to ensure the safety of aquaculture.In this study,based on electrochemical sensor detection technology,suitable modified electrodes were screened for three antibiotics,sulfadiazine,nitrofurazone and sulfadimethoxine,in the aquaculture water environment,and a rapid and convenient electrochemical detection method was established for the aquaculture seawater samples.The specific research results are as follows:(1)An electrochemical sensor for the detection of sulfadiazine(SDZ)in cultured seawater was constructed based on glassy carbon electrode(GCE).The electrochemical performance of the electrode was characterized using differential pulse voltammetry(DPV)and cyclic voltammetry(CV).Among the four substrates,NaCl solution,acetate buffer solution,artificial seawater and phosphate buffer solution,the acetate buffer solution was determined as the best substrate and the optimal pH value was 4.0.Under the optimal experimental conditions,the method showed good detection of sulfadiazine in cultured seawater with good linearity between sulfadiazine and peak current intensity in the concentration range of 20 to 300 μM with a correlation coefficient of R2=0.994,a limit of detection(LOD)of 6.14 μM,and a recovery of 87%-95%.In addition,it showed good reproducibility and interference resistance by deep polishing of the electrode.(2)An electrochemical sensor for the detection of nitrofurazone(NFZ)in cultured seawater was constructed based on a glassy carbon electrode modified with nanogold(AuPNs).The amplification of the electrical signal was achieved by electropolymerization of nanogold on the electrode surface,which was characterized by scanning electron microscopy.The experimental conditions were optimized using DPV and square wave voltammetry(SWV).The optimal number of turns of the polymerized nanogold was determined to be 10 and the optimal pH of the phosphate buffer electrolyte was 5.0.Under the optimal experimental conditions,the constructed electrochemical sensor had a high current response intensity to nitrofurazone,and the sensor response current of this method was linearly related to the nitrofurazone concentration in the range of 3 μM-100 μM with a detection limit of 0.24 μM.(3)A molecularly imprinted electrochemical sensor based on multi-walled carbon nanotubes/graphene quantum dots(MWCNTs/GQDs)was constructed for the selective identification and detection of sulfadimethoxine(SMZ)in cultured seawater.The MWCNTs/GQDs were immobilized on the electrode by drop coating method,and the molecularly imprinted polymer(MIP)was prepared by electropolymerization to modify the electrode for amplifying the electrical signal and specific recognition.Finally,by optimizing the detection conditions,the optimal drop coating volume of MWCNTs/GQDs was determined to be 8 μL,the optimal number of elution turns of the elution template was 50,and the optimal pH of the acetate electrolyte was 9.0.The method was suitable for the detection of SMZ in cultured seawater and showed good linearity in the concentration range of 0.5-200 μM,with the detection limit of 0.068 μM and relative standard deviation(RSD)less than 5%.