A Prussian blue-carbon paste electrode for selective cathodic amperometric determination of nitrite using a flow-injection analysis system with carrier recycling

A selective, simple, and low cost method for nitrite determination was developed using an FIA system with a Prussian blue-carbon paste electrode (PB-CPE) as an amperometric detector. The electrochemical sensor was prepared by a fast, simple, and inexpensive procedure, and the long-term stability of the electrode was quite satisfactory as the performance was maintained over one year. PB acted as an effective redox mediator for nitrite electroreduction in acidic media, allowing nitrite detection at +0.2 V vs. Ag/AgClsat, a potential at which most possible interfering species are not electroactive. Consequently, the proposed method was completely free from interference from nitrate, dissolved oxygen, ascorbic acid, and other species usually present in water and food samples. The electrochemical cell used in the FIA system was similar to a batch injection analysis cell, enabling recirculation of the carrier solution. This is an attractive feature because it allows the use of a high flow rate (6 mL min(-1)) leading to high sensitivity and analysis speed, while keeping reagent consumption low. Under the optimized conditions, the proposed method had a detection limit of 9 mu mol L-1 and was successfully employed for nitrite quantification in water and sausage samples. For all analyzed samples, recovery percentages close to 100% were obtained, which is indicative of the accuracy and reliability of the proposed method. (C) 2015 Elsevier Ltd. All rights reserved.