Gas-diffusion Flow Injection Research Articles

Potentiometric and conductometric determination of ammonium by gas-diffusion flow injection analysis

Considerable enhancement of selectivity in the potentiometric and conductometric determination of ammonium is provided by gas-diffusion separation in flow injection analysis. Ammonium and potassium selective liquid membrane electrodes can be used for determinations in the concentration range 10−7–10−2 mol/l with high precision and fast sample throughput. No interferences are encountered in the presence of ionic species and molecules that likely adsorb when the sensors are in direct contact with the sample. The selectivity over volatile amines is enhanced due to kinetic discrimination. Conductometric detection is shown to be as sensitive as the potentiometric detection. A major advantage, however, is the linear rather than logarithmic relationship between concentration and conductivity.

Indirect determination of chloride by gas-diffusion flow injection with amperometric detection

A rapid, indirect gas-diffusion flow injection (FI) method with amperometric detection has been developed for the selective and sensitive determination of Cl–. The method is based on permanganate oxidation of Cl– to chlorine. The chlorine diffuses through the micro-porous membrane and is quantified amperometrically at a platinum working electrode. Calibration graphs were linear up to the maximum concentration of Cl– investigated (10 mmol dm–3). The precision of the technique was better than a relative standard deviation of 1% at 2 mmol dm–3 levels and better than 2% at 10 µmol dm–3, with a throughput of 30 samples h–1. At elevated temperatures (50 °C) and higher acidities (5 mol dm–3 H2SO4), the detection limit was 0.1 µmol dm–3(0.7 ng of Cl–). The effects of temperature, sample acidity, working potential and interferents on the FI signals were studied. The method was successfully applied to the determination of Cl– in natural and tap waters.

Utilization of adsorption-immobilized urease in gas-diffusion flow injection

A gas-diffusion flow-injection system for the assay of urea is reported. Urea is enzymatically converted to ammonia, which is determined spectrophotometrically by detecting the change in absorbance of a mixed pH indicator. The enzyme is immobilized by addition of perfluoroalkyl chains to the free amine groups of the enzyme and then adsorption of this modified enzyme on a polytetrafluoroethylene gas-diffusion membrane. The method is applicable in the range 0.1–500 mM urea. The procedure was used in comparison assays using blood serum samples.

Gas-diffusion separation and flow injection potentiometry

The similarities and differences of the operation principle of gas-sensing electrodes and potentiometric detection coupled to gas-diffusion separation in flow injection analysis are discussed with special emphasis on selectivity and sensitivity aspects. Several examples of application are presented highlighting the improvements in detectability obtained by gas-diffusion flow injection potentiometry. High sensitivity determination of ammonium is achieved through accumulation of ammonia released from the sample stream in the small recipient volume of the gas-diffusion unit. A method for almost specific determination of cyanide is presented making use of gas-diffusion separation of hydrogen cyanide and potentiometric detection with a selective AgI membrane electrode. The interference of sulfide is totally prevented by its oxidation in the donor line. If applied to potentiometric measurement following gas diffusion separation an intrinsically non-selective metallic silver wire electrode turns out to enable the selective detection of sulfide with high sensitivity and fast response. A new approach for diffusive sampling and on-line detection of gas-phase contaminants is exemplified by the determination of NOx.

Flow injection gas-diffusion method for preconcentration and determination of trace sulfide

A preconcentrating gas diffusion flow injection analysis (FIA) method with amperometric detection has been developed for selective determination of sulfide. The method is based on using the acceptor stream of the diffusion unit in a closed-loop, mobile (recirculating) mode for the accumulation of the analyte. In the analysis step the contents of the acceptor loop are injected into a sodium carbonate stream and are carried to the amperometric detector. The various flow patterns required for this method are regulated by a single eight-port rotary valve. The method developed has very low detection limits of 0.15 ..mu..g/L. The relative standard deviation for a 1 ..mu..g/L standard is 4%, and of the potential interferences tested, only cyanide had an effect.

Utilization of Dual Phase Gas Diffusion FIA with a Mass Spectrometer as a Detector

Abstract The coupling of dual phase gas diffusion flow injection analysis with mass spectrometry has been shown to be feasible. This combined technique offers a high degree of selectivity and sensitivity. This technique was developed to determine whether volatile mixed arsenic selenium hydrides are formed in dual phase gas diffusion flow injection analysis hydride generation.

Selective chlorine determination by gas-diffusion flow injection analysis with chemiluminescent detection

L'incorporation d'une membrane de diffusion de gaz dans le systeme d'injection en ecoulement permet d'eliminer les interferences causees par les autres especes ioniques (metal de transition, ions chlorure, chlorite et chlorate)

Optimization of parameters for gas-diffusion flow-injection systems

The effects of flow rate, flow direction, flow ratio, pressure, membrane area, channel depth and channel shape on the optimization of gas-diffusion flow-injection systems are described in detail. A nonreacting chemical system, chlorine dioxide, was used to study the physical dispersion of the gas-diffusion systems. It was found that slow flow rates and shallow channels are optimal. Stopped-flow conditions in a nonreacting chemical system may not be worth the cost in time. For chemical systems in which the analyte is consumed, the optimized parameters included stopped flow.

Selective chlorine dioxide determination using gas-diffusion flow injection analysis with chemiluminescent detection

An automated chemiluminescent technique has been developed utilizing the advantages of gas-diffusion flow injection analysis. A gas-diffusion membrane separates the donor (sampling) stream from the acceptor (detecting) stream and removes ionic interferences. A novel chemiluminescence flow-through detector cell is used to measure the concentration of chlorine dioxide as a function of the intensity of the chemiluminescence produced from its reaction with luminol. The chemiluminescent reagent merges with the analyte directly in front of the photomultiplier tube in order to maximize the sensitivity of the system. The detection limit for chlorine dioxide is approximately 5 ppb. The method is over 1500 times more selective for chlorine dioxide than for chlorine on a mole basis. This method eliminates interference from iron and manganese compounds, as well as other oxychlorinated compounds such as chlorite ion and chlorate ion.

Selective determination of chlorine dioxide using gas diffusion flow injection analysis

An automated absorbance technique for the determination of aqueous chlorine dioxide has been developed by utilizing gas diffusion flow injection analysis. A gas diffusion membrane is used to separate the donor (sampling) stream from the acceptor (detecting) stream. The absorbance of chlorine dioxide is monitored at 359 nm. The first method uses distilled water as the acceptor stream and gives a detection limit of 0.25 mg/L chlorine dioxide. This system is over 550 times more selective for chlorine dioxide than chlorine. To further minimize chlorine interference, oxalic acid is used in the acceptor stream. The detection limit for this system is 0.45 mg/L chlorine dioxide. This second system is over 5400 times more selective for chlorine dioxide than chlorine. Both methods show excellent selectivity for chlorine dioxide over iron and manganese compounds, as well as other oxychlorinated compounds such as chlorite and perchlorate ions. 18 references, 7 figures, 3 tables.

Residual aqueous ozone determination by gas diffusion flow injection analysis

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTResidual aqueous ozone determination by gas diffusion flow injection analysisMichael R. Straka, Gilbert. Gordon, and Gilbert E. PaceyCite this: Anal. Chem. 1985, 57, 9, 1799–1803Publication Date (Print):August 1, 1985Publication History Published online1 May 2002Published inissue 1 August 1985https://doi.org/10.1021/ac00286a004RIGHTS & PERMISSIONSArticle Views218Altmetric-Citations43LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts