Portable flow injection potentiometry (FIP) is described with a flow-through multi-ion sensor array system based on a planar design. Potassium, sodium and nitrate sensors are used as examples for simultaneous multi-ion determinations based on the availability of a planar sensor design for these ions. The miniaturized flow cell developed with thc three sensors in series in the FIP system is used to demonstrate the reliability of this portable design when using manual injection of the sample solution. The system is characterized by its small size, light weight and low power requirements, and makes use of a notebook computer for real-time display of data and data acquisition. Rapid FIP response characteristics are shown after optimization of flow carrier conditions, and are successfully applied to the analysis of mineral water samples.

An improved photo-cured membrane selective to calcium was developed based on the calcium bis[4-(l , I ,3,3-tetramethylbutyl)phenyl] phosphate ionophore and incorporates the lipophilic additive, potassium tetrakis(pchloropheny1)borate. The calcium electrode exhibited a hyper-Nernstian response of 31.0 mV change per activity decade and a log-linear range between 1 x lo-' to 0. I M in pure calcium chloride solution, in steady-state mode. The calcium electrode was fast responding, reaching 90% of steady-state value in 5 s making it ideal for flow injection measurements. The photo-cured electrode can measure calcium in a high perchlorate background, and was used to determine the total calcium level in full cream milk that was digested by a nitric/perchloric acid mixture. The results obtained were in good agreement with atomic absorption spectroscopy measurements.

No abstract

Nonactin and N,N-dioctadecylmethylamine ionophores, each in an epoxydiacrylate polymer, were photo-cured on silver wires (0.8 mm i.d.) and evaluated as ammonium and hydrogen (pH) coated wire electrodes. The photo-cured membranes prepared in this study exhibited excellent adhesion to the metal substrate and improved mechanical strength compared to PVC based membranes. The ammonium electrode exhibited a Nernstian response over a concentration range between 0.01 mM and 100mM with a detection limit of 0.0005mM. The ammonium electrode exhibited improved selectivity against most common interfering ions, including potassium compared to previous studies. The hydrogen selective electrode exhibited a near-Nemstian slope of 55.9 t 0.8 mV changellog a("+) between pH 4.0 and pH 1 I .O in the steady-state mode. The ammonium and pH sensors each responded quickly reaching 90 % of steady-state value in < 5 s, making these coated wire sensors ideal for flow injection potentiometry measurements. In the FIP mode, both the photo-cured ammonium and pH electrodes exhibited near-Nemstian responses of 49.2 t 1.0mV change I activity decade and 50.2 ? 0.4 mV change / log a(H+). respectively, over a similar concentration range as in the steady-state mode. The photo-cured ammonium and pH electrodes were used simultaneously in the analysis of hydroponic nutrient solutions and waste water samples obtained from a local greenhouse grower in the flow injection potentiometric mode.

In this study, a tungsten oxide wire electrode is described for use as a pH electrode in a portable battery-powered flow injection analyser described previously. 1 The tungsten oxide electrode exhibits a linear response of 44.8 ± 0.5 mV change per pH unit over a wide range, pH 2-11 in the steady-state mode. In the flow injection mode, the tungsten oxide wire electrode exhibited a slope of 42.4 ± 0.9 mV per pH unit. The tungsten oxide electrode was employed to determine the pH of various alcoholic beverages and environmental water samples.