Analysis of spironolactone residues in industrial wastewater and in drug formulations by cathodic stripping voltammetry

The redox behavior of spironolactone（SP） drug in Britton-Robinson（BR） buffer of pH 2-11 was investigated by differential pulse cathodic stripping voltammetry（DPCSV） and cyclic voltammetry（CV） at hanging mercury dropping electrode（HMDE）.At pH 9-10.5,the DPCSV of SP drug showed two cathodic peaks at1.15 and1.38 V at the HMDE vs.Ag/AgCl reference electrode.In the CV,at pH 9-10,the dependence of the cathodic peak current,Ip,c and peak potential,Ep,c of the second peak（Ep,c2） on the scan rate（n） and on the depolizer（SP） concentrations was typical of an electrode coupled（EC） chemical reaction type mechanism.The plot of Ip,cat 1.380 V of the DPCSV vs.SP concentration at pH 9 was linear over the concentration range of 1.2×1010-9.6×107 M.The lower limit of detection（LLOD） and limit of quantification（LOQ） of the drug were 1.1×1011 and 4.14×1011 M,respectively.The method was successfully applied for the analysis of SP residues in industrial wastewater,in pure form（98.273.1%） and in drug formulations e.g.Aldactones tablet（98.3572.9%）.The method was validated by comparison with HPLC and the official data methods.

Preparation and Electrochemical Properties of Pb-0.3wt%Ag/Pb-WC Composite Inert Anodes

We prepared Pb-0.3wt%Ag/Pb-WC（WC stands for tungsten carbide,the same below） composite inert anodes by double-pulse electrodeposition on the surface of Pb-0.3wt%Ag substrates,and investigated the electrochemical properties of the composite inert anodes,which were obtained under different forward pulse average current densities from 2 A/dm2 to 5 A/dm2 and WC concentrations from 0 g/L to 40 g/L in bath.The kinetic parameters of oxygen evolution,corrosion potential and corrosion current of the composite inert anodes were obtained in a synthetic zinc electrowinning electrolyte of 50 g/L Zn2＋ and 150 g/L H2SO4 at 35 ℃,by measuring the anodic polarization curves,Tafel polarization curves and cyclic voltammetry curves.The results show that Pb-0.3wt% Ag/Pb-WC composite inert anodes obtained under forward pulse average current density of 3 A/dm2 and WC concentration of 30 g/L in an original acid plating bath,possess higher electrocatalytic activity of oxygen evolution,lower overpotential of oxygen evolution,better reversibility of electrode reaction and corrosion resistance in [ZnSO4＋H2SO4] solution.The overpotential of oxygen evolution of the composite inert anode is 0.926 V under 500 A/m2 in [ZnSO4＋H2SO4] solution,and 245 mV lower than that of Pb-1% Ag alloy;the corrosion current of the composite inert anode is 0.95×10-4A which is distinctly lower than that of Pb-1%Ag alloy,showing the excellent corrosion resistance.