Flow injection determination of nitrite by graphene quantum dots

A simple, rapid and sensitive flow injection based spectrophotometric method has been applied for the determination of nitrite. The method is based on the fast reaction of nitrite with metoclopramide hydrochloride in acidic solutions to produce a diazonium cation which is subsequently coupled with graphene quantum dot, and forms a yellow colored azo product. The product absorbs electromagnetic radiation at 423 nm (λ_max). The dependency of absorbance to various instrumental and chemical parameters was investigated and the optimum condition was selected to prepare nitrite calibration graph. Beer's law was obeyed in the range of 0.02-7 μg mL-1. Various concentrations of nitrite were selected, and precision and accuracy of the method were evaluated. The obtained relative standard deviations and recoveries as percent were in the range of 1.5-6.1% and 97.8-99.2%, respectively. The method was successfully applied on the determination of nitrite in various water, sausage and cheese samples.