A POLAROGRAPHIC CATHODIC WAVE OF VITAMIN C

The cathodic wave of vitamin C has not been reported in the literature so far.Its E_(1/2)was found at-1.85 volt vs.Ag/AgCl(25℃)in the base solution of 0.1mol/L Bu_4NI.Various electrochemical and spectral techniques were used for studying the electrode reaction. They all showed that the electrode reaction was quasi-reversible while C was more than 1.0×10^(-6)mol/L and mainly adsorptive while C was less than 1.0×10^(-6)mol/L at a mercury electrode.The electron transfer number was 2 and the electron transfer coefficient 0.57. Using DPP techniques,the linear response range was 5.0×10^(-7)-2.0×10^(-3)mol/L and the detection limit 1×10^(-7)mol/L.

A POLAROGRAPHIC CATALYTIC WAVE OF OXYGEN INDUCED BY DIPHENYLAMINE COMPOUNDS

It is reported in this paper a polarographic catalytic double wave of oxygen reduction caused by diphenylamine compounds(diphs).The electrochemical process of the wave includes the polarographic generation of the superoxide anion O_2^- and the dismutation of O_2^- catalyzed by diphs with redox pseudoreversibility.

Polarographic Catalytic Wave of Lysozyme

This paper reports a polarographic catalytic wave of lysozyme (LE) in the presence of KIO3. The mechanism of the catalytic wave was discussed. It is illustrated by the catalytic wave of LE that, besides the Brdicka current, there exists a new kind of catalytic wave of protein.

Microwave digestion polarography for determining seven trace elements in Salvia Miltiorrhiza Root and compound Salvia Miltiorrhiza Root injection simultaneously

The sensitive second derivative waves of Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ),Ni(Ⅱ),Zn(Ⅱ),Fe(Ⅱ)and Mn(Ⅱ),forming in the substrate solution(pH=9.26)consisting of ammonia,ammonium chlorid,gelatin and ascorbic acid were researched.The peak potentials of the polarographic waves of the seven ions are at about 0.48,0.63,0.79,1.04,1.28,1.44 and 1.60 V respectively.Combining with microwave technique,a new method for the simultaneous determination of the seven trace elements in Chinese traditional medicine was developed.The method is easy to operate,rapid,simple and convenient.When the signal-to-noise rate equals 3,the detection limits of Cu,Pb,Cd,Ni,Zn,Fe and Mn are 4.2×10 3,5.3×10 3,2.1×10 3,5.8×10 4,3.0×10 3,7.7×10 4 and 1.1×10 3 μg/mL respectively.Well linear relationships exist between the concentrations and the peak currents when Cu,Pb,Cd,Ni,Zn,Fe and Mn concentrations are within 8.5×10 3 10,9.7×10 3 10,4.5×10 3 10,1.2×10 3 10,6.4×10 3 10,1.5×10 3 10 and 2.8×10 3 10 μg/mL,respectively.The method has been used to the simultaneous determination of the seven trace elements in Salvia Miltiorrhiza Root and compound Salvia Miltiorrhiza Root injection,the relative standard deviations(RSDs)of the Cu,Pb,Cd,Ni,Zn,Fe and Mn in the two medicines are 3.9% and 5.8%,4.0% and 4.1%,4.3% and 5.7%,4.9% and 5.3%,4.4% and 4.7%,3.5% and 4.0%,0.51% and 2.8%,respectively;the comparisons of the determination results with the values obtained by the standard method indicate that the presented method has very well veracity.

Study on Electroanalytical Chemistry of Rare Earths Part 1 Catalytic Wave of Yb^(3+)-MnO_4^--HClO_4 System

In the present paper, linear sweep polarography (LPS) was employed to study Yb 3+ KMnO 4 system. Results show that this system is characterized as a catalytic wave. The first step of Yb 3+ reduction was the one electron reduction to Yb 2+ , and improvement in the sensitivity of Yb 3+ was studied. Convolution voltammetry and cyclic voltammetry were employed to determine the rate constant and to confirm the process of electrode. The effects of various parameters, including pH, electrolyte, catalyst concentration and surface active substance on the reduction process were examined.

Study and Application of Polarographic Catalytic Wave of Chlordiazepoxide in the Presence of Persulfate

Polarographic catalytic wave of chlordiazepoxide in the presence of K 2S 2O 8 was studied in aqueous and DMF/H 2O mixed solutions. The results showed that a single reduction wave in alkaline medium was the reduction of the N=C bond in 1,2 position of chlordiazepoxide via an intermediate free radical in two one electron successive additions. When K 2S 2O 8 was present, the free radical of the N=C bond was oxidized to regenerate the original, producing a parallel catalytic wave of chlordiazepoxide. It was determined that the apparent rate constant k f of the oxidation reaction was 3.2×10 3 mol -1 ·L·s -1 . Using the catalytic wave the trace of chlordiazepoxide can be determined by linear potential scan polarography. In NH 3/NH 4Cl (pH 10.2±0.1, 0.12 mol/L)/K 2S 2O 8 (0.016 mol/L) supporting electrolyte, the second order derivative peak current of the catalytic wave was rectilinear to chlordiazepoxide concentration in the range of 3.20×10 -8 -1.60×10 -7 , 1.60×10 -7 -1.44×10 -6 and 1.44 ×10 -6 -1.44×10 -5 mol/L, respectively. The limit of detection was 9.0×10 -9 mol/L.

Investigation and Application of Polarographic Catalytic Wave of Oxygen Reduction Caused by Mefenamic Acid

The polarographic catalytic wave of oxygen reduction caused by mefenamic acid (MA) with redox properties was reported in this paper. The electrochemical process of the catalytic wave was proposed that the superoxide anion O(?) was generated polarographically and the dismutation of the O(?) was catalyzed by MA to reproduce O_2 and H_2O_2. This explained chemically the scavenging of the O_2^- by MA im biomedical area. Based on the catalytic wave, a new method for the determination of MA by single-sweep polarography was developed.