RESUMEN
Clinical studies had demonstrated that early diagnosis of lesion could significantly reduce the risk of cancer. Magneto-acoustic-electrical tomography (MAET) is expected to become a new detection method due to its advantages of high resolution and high contrast. Based on thinking of modular design, a low-cost, digital magneto-acoustic conductivity detection system was designed and implemented in this study. The theory of MAET using chirp continuous wave excitation was introduced. The results of homogeneous phantom experiment with 0.5% NaCl clearly showed that the conductivity curve of homogeneous phantom was highly consistent with the actual physical size, which indicated that the chirp excitation theory in our proposed system was correct and feasible. Besides, the resolution obtained by 1 000 μs sweep time was better than that obtained by 500 μs and 1 500 μs, which means that sweep time is an important factor affecting the detection resolution of the conductivity. The same result was obtained in the experiments carried out on homogeneous phantoms with different concentrations of NaCl, which demonstrated the repeatability of our proposed MAET system.
RESUMEN
By using Zinc nitrate as precursor and hydraZine hydrate as reducing agent, polydiallyl dimethyl ammonium chloride modified reduced graphene oxide/Zinc oxide composite materials ( PDDA-rGO/ZnO) were prepared by simultaneous reduction of graphene oxide ( GO) and Zinc nitrate.The composite materials were characteriZed by Fourier transform infrared ( FTIR ) spectroscopy, X-ray diffractometer ( XRD ) and transmission electron microscopy ( TEM) , and their electrochemical catalytic activity for uric acid was studied by cyclic voltammetry ( CV ) and linear sweep voltammetry ( LSV ) measurements.The result showed that PDDA-rGO/ZnO modified glassy carbon electrode prepared here was sensitive, reproducible and stable, and had significant electrocatalytic activity for UA.When using linear sweep voltammetry for detection of UA, the responses of modified electrode were linear with UA concentration in the ranges of 0.02-0.1 mmol/L and 0.1-1.0 mmol/L respectively, with detection limit of 15.9 nmol/L (S/N=3).
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This study was aimed to develop a simultaneous determination of zinc and cadmium with carbon fiber electrode by linear sweep stripping voltammetry. Effects of analytical base solution, accumulation potential, ac-cumulation time and scanning velocity were also investigated on the determination. The results showed that in 1 mol·L-1 H2SO4 medium solution, zinc and cadmium had good electrochemical response on the carbon fiber electrode and appeared sensitive anodic stripping peaks at-0.97 V and-0.77 V, respectively. The anodic stripping peak cur-rents and concentrations of zinc and cadmium showed good linear relationships, with correlation coefficients R2 of 0.996 5 and 0.995 4, respectively. The detection limits of zinc and cadmium (S/N=3) were 1.5×10-9 mol·L-1 and 1.0×10-10 mol·L-1, respectively. The average recoveries of zinc and cadmium were 98.9%and 98.1%with the rela-tive standard deviations (RSD) of 2.72%and 2.45%(n=6), respectively. It was concluded that the method of simul-taneous determination of zinc and cadmium with carbon fiber electrode was simple, sensitive and accurate.
RESUMEN
Objective To establish a new method for determination of Pb and Cd in sewage.Methods The contents of Pb and Cd in sewage were simultaneously determined by linear sweep anodic stripping voltammetry in0.1mol/L HCl -0.1mol/L KCl solution.Results The peak potentials of Pb and Cd appeared at-588mV and-780mV respectively.The recovery rates and precisions(RSD%)of Pb and Cd were90.0%-110.0%,91%-109.5%and0.41%-4.24%,0.56%-7.03%respectively.The lin-ear range of Pb and Cd was0.005-0.2mg /L.Conclusion This method could be applied for determination of Pb and Cd in sewage.