A novel third-generation hydrogen peroxide(H_2O_2) biosensor(Hb/CdS/MWNTs/GCE) was fabricated through hemoglobin(Hb) adsorbed onto the mercaptoacetic acid modified CdS QDs/carboxyl multiwall carbon nanotubes'(MWNTs) films.Cyclic voltammogram of Hb/CdS/MWNTs/GCE showed a pair of well-defined and quasi-reversible redox peaks with a formal potential(E^0) of-0.230 V(vs.Ag/AgCl) in 0.1 mol/L pH=8.0 phosphate buffer solution(PBS),which was the characteristic of the Hb heme Fe(Ⅲ)/Fe(Ⅱ) redox couple.The biosensor shows an excellent electrocatalytic activity to the reduction of H_2O_2.The response time of the designed biosensor to H_2O_2 at a potential of -0.30 V was less than 2 s and linear relationships were obtained in the concentration ranges of 2.0×10^(-6)—2.7×10^(-3) mol/L and 2.7×10^(-3)—7.7×10^(-3) mol/L with a detection limit of 3.0×10^(-7)mol/L(S/N=3).The apparent Michaelis-Menten constant K_m was estimated to be 1.324 mmol/L that illustrated the excellent biological activity of the fixed Hb.
Molecularly imprinted polymers(MIPs) were applied as molecular recognition elements to an electrochemical sensor for cinchonidine(CD).A kind of MIP was synthesized with cinchonidine as template,modified rosin(ethylene glycol maleic rosinate acrylate) containing the skeleton of phenanthrene rings as cross-linker and methylacrylic acid as functional monomer.MIP membrane was prepared on a glassy carbon electrode for the determination of CD via free radical polymerization method.Electrochemical impedance spectroscopy(EIS) and cyclic voltammetry(CV) were used to characterize the membrane electrochemical behavior in electrode fabrication process.The experimental conditions were discussed.Under optimum conditions,it was found that the response of peak currents was linear to the concentration of CD in a range of 0.013―2.26 mmol/L.The detection limit for CD is 1 μmol/L,the relative standard deviation for 100 μmol/L CD is 1.34% and the incubation time is 2 min.The sensor was applied to the determination of CD in urine samples with satisfactory results.
LIU LiTAN Xue-caiZHAO Dan-danWANG LinLEI Fu-houHUANG Zai-yin
A novel type of Fe3O4 nanoparticles modified glass carbon electrode(Fe3O4/GCE) was constructed and the electrochemical properties of N-(4-nitro-2-phenoxyphenyl)methanesulfonamide(nimesulide) were studied on the Fe3O4/GCE.In 0.4mol/L HAc-NaAc buffer solution(pH=5.0),the electrode process of nimesulide was irreversible at bare GCE and Fe3O4/GCE.The Fe3O4/GCE exhibited a remarkable catalytic and enhancement effect on the reduction of nimesulide.The reduction peak potential of nimesulide shifted positively from-0.683 V at bare GCE to-0.625 V at Fe3O4/GCE,and the sensitivity was increased by ca.3 times.Some experimental conditions were optimized.The linear range between the peak current and the concentration of nimesulide was 2.6×10-6 "1.0×10-4mol/L(R=0.993) with a detection limit of 1.3×10-7mol/L.This method has been used to determine the content of nimesulide in medical tablets.The recovery was determined to be 96.9% "101.9% by means of standard addition method.The method is comparable to UV-Vis spectrometry.
