Table of Contents

Abstract: Glassy carbon electrodes coated with Nafion are used for the ion-exchange voltammetric (IEV) determination of Fe(II) in the pore-waters and acidic extracts of sediments of the lagoon of Venice (Italy). The coated electrodes give reversible voltammetric signals, well resolved from background currents, which can be used for quantitative determinations. The yield of iron extracted by HCl from the sediment depends on the experimental conditions, in particular on the concentration of hydrochloric acid. By combining IEV on the acid extract with trapping and analysis of gaseous H2S evolved it is possible to obtain quantitative information both on the total content of iron dissolved by the acid attack and on the fraction of iron present in the form of acid volatile sulphides (AVS). As far as pore-waters are concerned, in this kind of samples the IEV determination of iron can be performed simply after dilution with HCl. The pore-waters here examined were sampled without alteration of their equilibrium conditions by using a suitable “in situ” sampler. IEV data obtained in samples from the lagoon of Venice (Italy) show satisfactory correlation with previous results obtained using different analytical techniques.

Abstract: A novel fiber-optic electrochemiluninescence sensor has been developed. It can be conveniently applied by placing into the sample solution in a manner similar to a conventional ion selective electrode, without requiring liquid luminous reagent and a flowing system. The sensor is consisted of an independent probe and a case for exclusion the ambient light, allowing the sample solution to pass through. Within the body of the probe, an optical fiber is utilized to collect and transmit light signal. In the three electrode configuration of the probe, a Pt electrode coated with Ru(bpy)₃²⁺- modified chitosan/silica gel membrane is used to give the electrolytic potential and provide a selective luminous membrane. The linear responses of the sensor to oxalic acid and amino acid were obtained in the concentration range of 2.0 × 10^-4 to 1.0 × 10 ^–2 mol/dm³ with the relative standard deviations of 3.5% and 5.7%, respectively. The response of the sensor was not less than 80% of the initial value after the service time was over one month.

Abstract: A system based on mechanical resonant filters is proposed that can be used for the detection of acoustical signals the frequency components of which vary according to specific periodic patterns. Usually, signals of this category produced by the siren of an emergency vehicle. The device essentially implements a mechanical narrow filter bank that covers the frequency range of a typical siren sound. Signal detection is obtained by measuring the time delay between successive activation of the filters of the bank. The whole analysis reveals how a set of simple, low-cost mechanical resonant filters can replace an electronic analog or digital system for the implementation of a filter bank. Moreover, a scaling down procedure is proposed so that a microsystem may be developed.