Pneumatoamperometric determination of nanogram amounts of cyanide

Abstract

Part-per-billion levels of cyanide react rapidly and quantitatively with excess Iodine at pH ~6.0 to form Iodine cyanide. The excess Iodine Is selectively removed from solution by nitrogen purging. Acidification of the resultant iodine cyanide solution with perchloric acid In the presence of iodide to a final concentration of 3.0 M HCI04 and 1.0 X 10~4 rapidly and quantitatively regenerates Iodine in an amount equivalent to the original cyanide. This iodine is transferred to the gas phase by purging with nitrogen, where It Is determined at a gold gas porous electrode by electro-oxidation to lodate. The detection limit for cyanide is estimated to be 5 ng In a 4-mL sample.

Microelectrodes coated with ionically conducting polymer membranes for voltammetric detection in flowing supercritical carbon dioxide

“…Several recent reports concerning voltammetry in resistive media suggested to us a way of achieving the goal of a voltammetric sensor in flowing supercritical fluid. Metal electrodes supported on ionically conducting polymer membranes have been used to conduct voltammetry of species extracted from gases (6) or electrolyte-free nonpolar organic solvents (7,8). In these studies, the membrane served as a separator between a vapor or solvent containing the electroactive substrate and an aqueous electrolyte solution containing auxiliary and reference electrodes.…”

“…The conversion of an analyte from a solution species to a gaseous product is the basis of cold vapor and hydride generation techniques. In both of these techniques, sensitivity and detection limits are significantly improved over more conventional nebulization modes (6). Gaseous analyte is also produced and quantified by using a heated graphite atomizer (7).…”

Voltammetry without supporting electrolyte using a platinum working electrode supported on an ion exchange membrane

“…Gas diffusion electrodes incorporating a solid polymer electrolyte (13)(14)(15)(16)(17) have found application in fuel cells and as gas sensors. A related concept is pneumatoamperometry in which volatile analytes pass through a hydrophobic porous membrane to reach the detection electrode (18)(19)(20)(21)(22).…”

Flow-injection analysis of volatile, electroinactive organic compounds at a platinum gas diffusion membrane electrode by the use of a redox mediator

“…This species either is the original sample component or is generated by a chemical reaction. It can either be in a gas (1)(2)(3)(4)(5)(6) or liquid (7,8) carrier stream and is determined after it passes through a gas-permeable, hydrophobic membrane to an electrode. This scheme is shown in Figure 1 of ref 7), where Y is the volatile species.…”