Thin Layer Coulometry of Nitrite with Ion‐Selective Membranes

Abstract

We report on a thin layer coulometric detection method based on an ion-selective membrane in view of a quantitative determination of nitrite in undiluted human urine and tap water. A cobalt(II) tert-butyl salophen compound, previously characterized by our group in ion-selective membrane electrodes, is used here as ionophore. The four orders of magnitude discrimination of chloride permits the detection of nitrite in samples that contain a large excess of chloride. The approach developed here allows one to determine nitrite within a concentration range of 20–100 µM for a 120 s current integration time. A modification of the reported electrochemical protocol to reduce the capacitive contribution diminishes the intercept of the calibration to −8.6 µC. This is especially important in view of reaching calibration free systems. Initial in-house validation exhibits a limit of detection of 10 µM in undiluted urine and in tap water. These values correspond to the regulation limits established in European Union and are adequate for the determination of nitrite for medical applications

Electroanalysis with Membrane Electrodes and Liquid–Liquid Interfaces

“…The methodology was also used to demonstrate the coulometric detection of nitrite, using a cobalt tert-butyl salophene ionophore in the membrane. 114 This work further reduced the nonzero intercept of the calibration curve by identifying the potential dependent charge as a capacitive contribution and subtracting its value from the observed charge to identify the faradaic contribution. Measurements in physiological samples were demonstrated, with detection limits on the order of 10 μM.…”

Reliable SERS detection of nitrite based on pH and laser irradiance-dependent diazotization through a convenient sampling micro-chamber

“…Nitrites as food additives have been strictly controlled under the safe level, because excessive nitrite intake can lead to the formation of a strong cancerogen nitrosamine, and reduce the ability of heme carrying oxygen. 1,2 Furthermore, food being stored for long periods also release nitrites by the nitro process of bacteria, which make the early, real-time and quantitative control of nitrites from food or drinking already a big issue. 3 Nitrite is usually detected and analyzed by the Griess reaction, 4 which involves the formation of a deep red-colored azo dye upon treatment of a nitrite-containing sample with sulfanilic acid and naphthyl-1-amine in the presence of acid.…”

From Molecular and Emulsified Ion Sensors to Membrane Electrodes: Molecular and Mechanistic Sensor Design

“…Different approaches have been proposed to decrease the sample phase dimensions, such as sampling with a paper support 44 or microfluidic devices with tubular shaped ISE membrane. 42,43,45 Alternatively, membranes thinner than 1 µm have allowed for the establishment of ion-transfer voltammetry as an alternative readout of ionophore-based ISEs.…”