Electrochemical Behavior of Mitoxantrone and Its Determination at a Pt/C Implanted Modified Microelectrode

In a 0.02 mol/L Na_2HPO_4-KH_2PO_4(PBS) buffer solution(pH=6.82), the electrochemical behavior of mitoxantrone was studied by linear-sweep voltammetry and cyclic voltammetry at a Pt/C ion implantation modified microelectrode. A sensitive reduction peak was observed. The peak potential was \{-0.72 V\}(vs.SCE), the peak current was proportional to the concentration of mitoxantrone within the ranges of 7.0×10 -8—9.0×10 -7 mol/L and 1.0×10 -6—2.4×10 -5 mol/L, with a detection limit of 4.0×10 -8 mol/L. The linear correlation coefficients were 0.9994 and 0.9992, respectively. This method has been applied to the direct determination of mitoxantrone in simulated urine. The recoveries were in the range from 96.2% to 105.9%. The reduction process was a quasi-reversible one with adsorptive characteristics at the Pt/C microelectrode. The electrode reaction rate constant k_s and the electron transfer coefficient α of the system were determined to be 4.5 and 0.65 s -1, respectively. The experiments showed that Pt element had surely been implanted into the surface of the carbon fiber, and the atomic Pt improved the electrocatalytic activity. The Pt/C microelectrode had a good stability and reproducibility.

Use of microelectrodes for electrochemical measurement of nitric oxide in natural seawater

In this paper, the application of a homemade Nafion and Co(Salen) modified platinum microelec-trode and an ISO-NOPMC microsensor (World Precision Instruments, USA ) to measure nitric oxide in natural seawater is reported. These two microelectrodes are suitable for the measurement. In natural seawater, the sensitivity and stability of the ISO-NOPMC microsensor are higher than that of the homemade Nafion and Co(Salen) modified platinum microelectrode.

Decomposition mechanism of pentlandite during electrochemical bio-oxidation process

Electrochemical measurements were carried out to elucidate decomposition mechanism of pentlandite using modified powder microelectrode with Acidithiobacillus ferrooxidans attached or without on the mineral powder surface.Cyclic voltammetry（CV） results show that at a low potential of about-0.2 V（vs SCE）,the pentlandite was transformed to an intermediated phase like Fe4.5-yNi4.5-xS8-z when Fe and Ni ions were evacuated from mineral lattice;when the potential was changed from-0.2 V to 0.2 V,the unstable violarite（Fe3Ni3S4） and FeNi2S4 were formed which was accompanied by element sulfur formed on the mineral surface;when the potential increased over 0.2 V,the unstable intermediated phase decomposed entirely;at a higher potential of 0.7 V,the evacuated ferrous ion was oxidized to ferric ion.The presence of Acidithiobacillus ferrooxidans made the oxidation peak current increase with initial peak potential negatively moving,and the bacteria also contributed to the sulfur removing from mineral surface,which was demonstrated by the reduction characteristic at potential ranging from-0.75 to-0.5 V.Leaching experiments and electrochemical results show that the solution acidity increasing when pH2 may impede the oxidation process slightly.

Evaluation of adsorption capacities of humic acids extracted from Algerian soil on polyaniline for application to remove pollutants such as Cd(Ⅱ), Zn(Ⅱ) and Ni(Ⅱ) and characterization with cavity microelectrode

The adsorption capacities of new humic acids isolated from Yakouren forest （YHA） and Sahara （Tamenrasset： THA） soils （Algeria） and commercial humic acid （PFHA） on polyaniline emeraldine base （PEB） were studied at pH 6.6. Also the adsorption of heavy metals such as Cd 2＋ , Zn 2＋ and Ni 2＋ on humic acid-polyaniline systems （HA-PEB） was investigated at the same conditions. HA-PEB compounds were characterized by scanning electron microscopy （SEM）, infrared spectrometry and cavity microelectrode. In addition, batch adsorption and cavity microelectrode were used in the adsorption study of Cd 2＋ , Zn 2＋ and Ni 2＋ on HA-PEB. To develop biocaptors of polluting metals using a cavity microelectrode modified by HA-PEB systems, the adsorption kinetic and adsorption capacity were investigated. The SEM analysis showed that the presence of humic acid affected the PEB surface and caused the formation of a granular morphology. The maximum adsorption capacities （q max ） of PFHA, THA and YHA determined by adsorption isotherms were 91.31, 132.1 and 151.0 mg/g, respectively. Batch adsorption results showed that q max of Cd 2＋ , Zn 2＋ and Ni 2＋ on HA-PEB followed the order： THA-PEB YHA-PEB PFHA-PEB. The voltammograms obtained with HA-PEB modified cavity microelectrode showed the appearance of new redox couples reflecting the adsorption of HA on PEB. Metal-humic acid-polyaniline voltammograms were characterized by appearance of oxidation-reduction couples or reduction wave corresponding to metal. Finally, the result may be exploited to develop a biocaptor based on the cavity microelectrode amended by THA-PEB and YHA-PEB.