High sensitivity voltammetric determination of sodium nitroprusside at acetylene black electrode in the presence of CTAB

A sensitive electroanalytical method for detection of sodium nitroprusside (SNP) was investigated, on the basis of the enhanced electrochemical response of SNP at an acetylene black electrode (ABE) in the presence of cetyltrimethylammonium bromide (CTAB). Voltammetric studies showed that SNP exhibited a pair of quasi-reversible redox peaks at ABE in the presence of CTAB while no any redox peak was observed in the absence of CTAB. This was attributed to the enhanced adsorption of SNP at AB through electrostatic interactions between SNP and CTAB as well as hydrophobic adsorption of CTAB at the hydrophobic surface of ABE. Under optimal working conditions, the reduction current was proportional to the concentration of SNP in the range of 1.0x10(-7) to 1.0x10(-5) mol/L and 1.0x10(-5) to 1.0x10(-2) mol/L. A low detection limit of 5.0x10(-9) mol/L was obtained for 2 min accumulation at open circuit (S/N=3). The proposed method was successfully applied to the determination of SNP in pharmaceutical dosage forms.