Colorimetric determination of hydrazine and nitrite using catalytic effect of palladium nanoparticles on the reduction reaction of methylene blue

In this research, hydrazine and nitrite determination was performed based on the reaction of methylene blue with hydrazine in the presence of palladium nanoparticles (PdNPs) as catalyst. The system was monitored spectrophotometrically by measuring the decrease in the absorbance of the methylene blue at 662 nm. Subsequently the inhibitory effect of nitrite on this catalytic reaction was also used for nitrite determination. In fact the depigmentation of methylene blue was postponed by nitrite added to the reaction mixture containing methylene blue, hydrazine and PdNPs. This inhibitory effect enables us to measure nitrite. Several factors influencing the analytical performance of the kinetic method such as concentration of reactants and electrolyte, pH of the sample solution and temperature were studied to achieve the optimum conditions and highest sensitivity. The change in absorption intensity of methylene blue was linearly proportional to the concentration in the range of 6-600 mu mol L-1 and 0.3-14.2 mu mol L-1 with a limit of detection of 3.85 mu mol L-1 and 0.21 mu mol L-1 for hydrazine and nitrite, respectively. The method was successfully applied to the determination of hydrazine in water samples and nitrite in water, meat and saliva samples.