A high-efficiency cathodic sodium nitroprusside/luminol/HO 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 HO to generate reactive oxygen species, which subsequently reacts with luminol to produce intense ECL. The ECL signal of the new SNP/HO/luminol system under neutral conditions (pH 7.4) is almost equivalent to the classic luminol/HO system at pH 10, making this system highly attractive for bioanalysis that directly or indirectly liberates HO under neutral conditions. At the optimum experimental conditions, the ECL intensity increases proportionally with the log of HO 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 HO is 4.25%. Recoveries from 97.2% to 101.7% were obtained for real sample analysis. Since HO 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 HO 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.