Abstract
A poly(N-methylpyrrole) based ion selective electrode (ISE) has been prepared by electro-polymerization of N-methylpyrrole using potassium nitrate as the supporting electrolyte. Electrochemical and chemical variables were used to optimize the potentiometric response of the electrodes and to maximize the selectivity for nitrate over potential interferences. The selectivity, longevity and stability of the ion-imprinted polymer give this electrode advantages over traditional nitrate ISEs. The best prototype electrode exhibits a linear potential response to nitrate ion within the concentration range of 5.0 × 10−6 to 0.1 M nitrate with a near Nernstian slope of −56.3 mV per decade (R2 = 0.9998) and a strong preference for the nitrate ion over other anions. The selectivity coefficients of the electrode were evaluated by the fixed interference method. The use of N-methylpyrrole has advantages over pyrrole in terms of selectivity and pH insensitivity.
Highlights
Nitrate is an important ingredient in fertilizers
It was originally thought that an organic modifier was needed to obtain dissolution of the N-methylpyrrole, so the solutions were made using a 50:50 mixture of acetonitrile and water. (It was later discovered that N-methylpyrrole would dissolve to the extent required in deionized water.) The current values ranged from 10 μA to 120 μA
Poly(N-methylpyrrole) can be ion imprinted by electro-polymerization of N-methylpyrrole using potassium nitrate as the supporting electrolyte
Summary
Nitrate is an important ingredient in fertilizers. many species are susceptible to nitrate poisoning. The Environmental Protection Agency (EPA) has set the Maximum Contaminant Level (MCL) of nitrate as nitrogen at 10 mg/L and for nitrite 1 mg/L for the safety of drinking water [1]. The flora in the digestive tract of ruminants produces a significant amount of nitrite. This may result in anoxia since nitrite can oxidize the ferrous ion in hemoglobin to produce stable methemoglobin that is unable to transport oxygen. Nitrate contamination in ground water can result in such a large decrease in oxygen carrying capacity of hemoglobin and in babies it may lead to death. The oral flora reduces some of the nitrate to nitrite. The bioavailability of ingested nitrate in vegetables has been determined to be 100% [3]
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