Telis Dimitrakopoulos

A Six Sensor Array of Coated‐Wire Electrodes for Use in a Portable Flow Injection Analyzer

An array of five photo-cured epoxydiacrylate membrane based coated-wire electrodes and a Ag/AgCl wire electrode used as a chloride sensor were all used simultaneously in a previously reported multielectrode flow cell and in a portable flow injection analyzer [1]. Photo-cured coated-wire electrodes for ammonium, calcium, hydrogen (pH), nitrate and potassium and Ag/AgCl wire based chloride electrode were developed for remote-site monitoring. The photo-cured membranes prepared exhibited strong adhesion to the metal substrate and showed improved mechanical strength compared to poly(vinyl chloride) based membranes. Each sensor in the present electrode-array exhibited near-Nernstian response over a log-linear range of between 0.1 mM and 10 mM with detection limits of 0.01 mM in the flow injection potentiometric mode. The flow injection cell was capable of determining the respective ions in various water samples and the results were in good agreement with comparative analytical methods.

Field-portable flow-injection analysers for monitoring of air and water pollution

There has been a rapid growth in the development of field-portable analytical instrumentation capable of in-situ and real-time feedback of data from remote sites. Advances have been made in applications for many technologies aided by developments in electronics, computing and telecommunications systems. This report presents a brief review of these developments and particularly of portable flow-injection systems applied in both the liquid and gas phase modes of operation with potentiometric sensors and gas sensors of the tin-oxide semiconductor types.

A tungsten oxide coated wire electrode used as a pH sensor in flow injection potentiometry

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.

Operational assessment of a potentiometric eight‐sensor flow cell in a portable flow injection analyzer

The evaluation of a novel eight-sensor flow cell used in a portable battery-powered flow injection potentiometry system is described. The portable flow injection system is small in size, light weight, requires low power, and uses a notebook computer for real-time display of data and data acquisition, making it practical for remote site monitoring. The electrode response for each sensor was evaluated in terms of flow rate and injection sample volume with silver and iodide standard solutions, each in a 0.1-M sodium acetate background. The mean electrode slopes observed for silver and iodide ions were 57.4 ± 1.0 and 47.5 ± 4.4 mV per activity decade, respectively. Potential applications include multiion capability with eight different liquid-membrane-based electrodes or operation of the measuring electrodes in an additive mode for improved sensitivity and detection limit for a single analyte.

Testosterone Determination Using Rapid Heterogeneous Competitive-Binding for Enzyme-Linked Immunosorbent Assay in Flow Injection.

The application of a rapid competitive enzyme-linked immunosorbent assay (ELISA) for the measurement of testosterone in flow injection (FI) is presented. The ELISA protocol for the determination of testosterone was performed in 60 min compared to the standard protocol time of 150 min. This was achieved by reducing the antibody incubation time. The ELISA was used successfully to determine testosterone levels in clinical samples of both male and female subjects, and were in good agreement compared to a pathology laboratory which employed an immunoradiometric assay (IRMA).

Simultaneous determination of total calcium and phosphorus in milk using flow-injection analysis

The design, development, and testing of a flow-injection analysis (FIA) manifold for the simultaneous determination of two species in milk samples is reported. Calcium is determined potentiometrically, and, following on-line sample treatment, spectrophotometric analysis of phosphorus is performed. Results obtained are consistent with manufacturers’ estimates and, in the case of calcium, with atomic spectrophotometric measurements. The combination FIA system is a rapid, low-cost, highly reproducible method that uses small sample volumes and could be used to provide on-site near-real-time measurements.