Biosensing Of Glycerides And Phenolic Compounds Based On Enzymes Modified Electrodes

Recently, the enzyme sensors, as an important kind of biosensors, have beendeveloped in many research and applications fileds. For its high bioaffinity,sensitive, sepcific substrate molecular recognition, and even detect of mixedsamples without any sample pretreatment, the enzyme sensors may beccome moreand more important in many applications.This thesis includes:1. Development of monolein enzyme-biosensor using lipase modifiedscreen-printed electrode （SPE）Lipase modified SPEs were prepared with optimum concentration of optimalPBS pH value is6.0, the best modification amount of lipase is0.7798μg. Monoleinwas determinated by cyclic voltammetry. The calibration curve of oxidation peakswas: ipa=1.8578lgC-4.3144, the correlation coefficient R is0.9979,while thecalibration curve of reduction peaks was: i=-2.0265lgC+2.1723, R=0.9979, withlinear detection range from0.5to3.0g L^-1. By chronocoulometry method, thecalibration relationship between△Q and concentration of monolein was:△Q=0.512lgC-0.2815, R=0.9977, with linear detection range from0.5to3.0g L^-12. Glyceryltrioleate biosensor based on lipase modified SPEA rapid method for determination of glyceryltrioleate was designed by usingSPE modified by lipase as an electrochemical biosensor. Cyclic voltammetry andchronocoulometry were applied to characterize the reaction betweenglyceryltrioleate and immobilized lipase. The optimal reaction conditions such aspotential window, pH of buffer, amount of immobilized lipase were carefullyinvestigated. Under the optimized conditions, the linear ranges are0.01⁵mg·mL^-1with detection limit （DL） of2.5×10^-3mg·mL^-1（for CV）, and1.0×10^-35.50mg·mL^-1with DL2.0×10^-4mg·mL^-1（for CC）. The method was used in thedetermination of6sunflower seed oil samples with recoveries of94.4%¹05.2%,successfully.3. Catechol biosensor based on Tyr@SiO₂/NiO-SPEPreparing a catechol sensor based on tyrosinase modified screen-printedcarbon electrode. Tyr@SiO₂/NiO-SPE was prepared as follow: using an electrochemical oxidation method, NiO was modified onto surface of SPE（NiO-SPE）, and then, a mixture of tyrosinase and mesoporous silica was coated onNiO-SPE. The standard curve for i=4.34C+9.49×10^-6, the linear correlationcoefficient R=0.9896. The linear detection range of10^-910^-3mol L^-1, and a limitdetection of2.5×10^-10mol L^-1.4. Catechol biosensor absed on Tyr@SiO₂/GCEHere, a tyrosinase@mesoporous silica modified glassy carbon electrode wasintroduced as an electrochemical biosensor to determinate catechol. The standardcurve of catechol is i=212.589C+0.5973, linear correlationcoefficient R=0.9962.The linear dynamic range from10^-10to10^-2mol L^-1, and a limit of detection of0.52×10-11mol L^-1resulted from CV measurements; and the standard curve ofcatechol is i=-0.2631C+8.2162resulted from i-t method. Using CV with standardaddition recovery method, three real samples （teas） were investigated carefully.