Chronocoulometric determination of nitrate on silver electrode and sodium hydroxide electrolyte

Abstract

An electrochemical system that consists of a silver electrode in 0.01 M sodium hydroxide electrolyte was investigated in an effort to develop a sensitive in situ analytical method for nitrate. Cyclic voltammetry demonstrated that the proposed system has a high normalized sensitivity (2.47 A s(1/2) V(-1/2) M(-1) cm(-2)), compared to more complex electroanalytical schemes. Double-potential-step chronocoulometry was used to maximize the signal-to-noise ratio (SNR), and minimize interference from dissolved oxygen in the electrolyte. The integration period for double-potential-step chronocoulometry was determined by optimizing the extended Cottrell equation. The integrated current is proportional to nitrate up to 10 mM and the average detection limit is approximately 1.7 microM. Dissolved oxygen does not degrade performance. To examine the potential interference of other ions when analyzing nitrate, we measured the electrode response to 1000 microM each of NO(2-), Cl(-), PO(4)(3-), SO(4)(2-), F(-), CO(3)(2-), BO(2-), K(+), Ca(2+), and Sr(2+) with and without 1000 microM nitrate. Interference is negligible for most of the ions when nitrate is absent (i.e. <1% of the response to equimolar nitrate). However, interference is substantial (>20% increase or decrease in the electrode response to nitrate) for PO(4)(3-), Ca(2+), and Sr(2+) when equimolar nitrate is present.

Comparison of nanostructured silver-modified silver and carbon ultramicroelectrodes for electrochemical detection of nitrate

“…The main challenge that most polarography/voltammetry-based electrochemical sensors faces is the electrode material's low activity for nitrate reduction; a catalyst is often required to achieve direct reduction of nitrate at a less negative potential. Furthermore, dissolved O 2 could interfere with the analysis; purging the sample solution with an inert gas is thus required [17]. These challenges, if not mitigated or improved upon, could lead to poor sensor performance and inaccurate quantification of the target analyte.…”

Voltammetric determination of nitrate in water samples at copper modified bismuth bulk electrode

“…acidic solution [39][40] and nitrite in alkaline solution [21]. NO À 3 reduction in sufficient acidic conditions can occur as an eight-electron process according to the following equation [13]:…”

“…Comparatively, voltammetric/amperometric techniques depend on the electrochemical reduction of NO À 3 at electrode surfaces. Various substrate materials such as copper [9][10][11][12][13][14], nickel [15], copper-nickel alloys [16], copper-palladium alloys [17], platinum [18,19], lead [20], silver [21], rhodium [22], boron-doped diamond [23][24][25], gold [26,27] and integrated electronic tongue [28] have been used. But, owing to slow kinetics of charge transfer, direct reduction of NO À 3 on bare unmodified electrodes is usually difficult.…”

Microfluidic Polymer Chip with an Embedded Ion-Selective Electrode Detector for Nitrate-Ion Assay in Environmental Samples

“…The most pervasive source of contamination by nitrate for water supplies is fertilizer runoffs to streams, and diary farm feces that leach into groundwater. 1,2 The determination of nitrate in aqueous solutions is very important because nitrate ingestion above a critical level causes significant clinical problems, such as methemoglobinemia in infants, bladder cancer, gastric cancer, and leukocyte enzyme abnormality. [2][3][4] The determination method of nitrate ions, based on spectrometry, [5][6][7][8][9] fluorometry, 10,11 atomic absorption spectrometry 12,13 and ion chromatography, 14 requires expensive instrumentation.…”