Electrochemical reduction of nitroprusside on a glassy carbon electrode modified by poly-l-lysine films

A high-efficiency cathodic sodium nitroprusside/luminol/H2O2 electrochemiluminescence system in neutral media for the detection of sodium nitroprusside, glucose, and glucose oxidase

Sodium nitroprusside (SNP) is an anti-hypertension drug used in vascular surgery, chronic cardiovascular disease, and in the management of acute myocardial infarction by the spontaneous release of nitric oxide. Herein, for the first time, we extend its application to electrochemiluminescence (ECL). The NO generated from the electrochemical reduction of SNP reacts with H₂O₂ to generate reactive oxygen species, which subsequently reacts with luminol to produce intense ECL. The ECL signal of the new SNP/H₂O₂/luminol system under neutral conditions (pH 7.4) is almost equivalent to the classic luminol/H₂O₂ system at pH 10, making this system highly attractive for bioanalysis that directly or indirectly liberates H₂O₂ under neutral conditions. At the optimum experimental conditions, the ECL intensity increases proportionally with the log of H₂O₂ and SNP concentration over the range from 0.2 μM-1000 μM and 0.08 mM-1.8 mM with the detection limits of 0.078 μM and 0.038 mM, respectively. The RSD for ten analyses of H₂O₂ is 4.25%. Recoveries from 97.2% to 101.7% were obtained for real sample analysis. Since H₂O₂ participates in numerous important enzymatic reactions, the application of this system was further investigated using glucose oxidase (GODx) and glucose as a representative enzyme and substrate, respectively, thus liberating H₂O₂ as a reaction product. The concentrations of glucose and the activity of GODx were directly proportional to the ECL intensities over a range of 5-1000 μM and 0.0025-1 units per mL with the limits of detection of 2.65 μM and 0.0012 units per mL (S/N = 3), respectively.

Voltammetric Study of the Copper Pentacyanonitrosylferrate Adsorbed on the Silica Modified with a Poly(propylene)imine Hexadecylamine Dendrimer for Determination of Nitrite

Poly(propylene)imine hexadecylamine dendrimer (DAB-Am-16) was anchored on the surface of 3-chloropropylsilyl silica gel and subsequently interacted with copper nitroprusside. The composite was characterized by infrared (FTIR), energy dispersive X-ray (EDX), and cyclic voltammetry. The above techniques confirmed the successful anchoring of the dendrimer on the silica gel modified surface and its interaction with copper nitroprusside. The cyclic voltammogram of CuNPSD was found to exhibit two redox couples with (Eθ′)1= 0.30 V and (Eθ′)2= 0.78 V versus Ag/AgCl ( mol L−1;  mV s−1) attributed to the redox processes and , respectively. The CuNPSD-modified graphite paste electrode was found to show a linear response of to  mol L−1for nitrite determination with a detection limit (DL) of  mol L−1and an amperometric sensitivity of 25.0 mA/mol L−1. The CuNPSD-modified graphite paste electrode was found to show a good electrochemical stability and an excellent response to the electrocatalytic oxidation of sodium nitrite.