G. Micali

Vanadium Oxide Sensing Layer Grown on Carbon Nanotubes by a New Atomic Layer Deposition Process

A new atomic layer deposition (ALD) process was applied for the homogeneous coating of carbon nanotubes with vanadium oxide. It permits the coating of the inner and outer surface with a highly conformal film of controllable thickness and, hence, the production of high surface area hybrid materials at a so far unprecedented quality. The ALD-coated tubes are used as active component in gas-sensing devices. They show electric responses that are directly related to the peculiar structure, i.e., the p-n heterojunction formed between the support and the film.

Citrus waste recovery: a new environmentally friendly procedure to obtain animal feed

Citrus juice centrifugation pulp is the semi-solid product obtained from the industrial centrifugation of juices, to obtain a clear juice. This waste causes many economic and environmental problems because of its fermentability. In this paper we describe a method which makes it possible to obtain animal feed from citrus juice centrifugation pulp. To this end, alkaline and/or enzymatic treatments were carried out on the centrifugation pulp. These treatments facilitate pressing and so help to produce a material which, using suitable methods, may be dried. Enzyme treatment proved to be the most efficient of the methods under investigation designed to favour the pressing of the pulp. The product obtained with this method showed excellent digestibility in vitro and its protein content, although not especially high, compared favourably with that of many other agroindustrial waste products currently used as components of animal feed.

High-performance liquid chromatographic profiles of aloe constituents and determination of aloin in beverages, with reference to the EEC regulation for flavouring substances

Characteristic HPLC profiles of fresh and aged aloe solutions, detected at 360 and 220 nm, are presented and compared. Several aloe constituents (aloesin, aloeresin A, hydroxyaloin, aloin A and B and aloinoside A and B) were simultaneously separated and identified. The determination of aloin is described (detection limit 0.15 ppm) and discussed. In aloe-based alcoholic beverages, the aloins could not be detected, owing to their instability and degradation in solution; this is discussed in relation to the EEC Council Directive 88/388, which fixed the values of maximum allowable concentrations for aloin in food and beverages. Instead of aloin, other aloe compounds (e.g., aloeresin A or aloesin) should perhaps be used as an index of the presence of aloe in alcoholic beverages.

High-performance liquid chromatographic determination of the biologically active principle hypericin in phytotherapeutic vegetable extracts and alcoholic beverages

Hypericin was determined using an RP C18 (3 microns) column 8.3 x 0.4 cm I.D.), thermostated at 50 degrees C. The separation was achieved with programmed elution using phosphate buffer (pH 7)-methanol (3:7) and watermethanol (3:7) as eluents. Fluorimetric detection was carried out with excitation at 470 nm and emission at 590 nm. The analytical sample was prepared by simple dilution in methanol of the phytotherapeutic extract or of the alcoholic beverage. Hypericin can be rapidly and accurately determined at concentrations down to 0.1 mg/kg without any interferences.

Design and Development of a Breath Acetone MOS Sensor for Ketogenic Diets Control

The design of a handy and noninvasive measurement of acetone in the human breath, which is useful for ketosis monitoring and control, by means of MOS sensors is reported. For this aim, highly sensitive resistive sensors in thick film configuration, fabricated depositing sensing layers of In2O 3 and Pt-In2O 3 nanopowders by screen-printing, have been developed. The devices were calibrated using standard gases in the laboratory, showing high sensitivity and a linear response in the range of acetone concentration investigated (1-100 ppm). The results obtained indicate that MOS sensors based on Pt-In2O 3 nanopowders are promising as fast and quantifiable means of determining acetone in the breath, posing the advantages of real time measurements and low costs devices for the control of ketogenic diets.

High-performance liquid chromatographic separation and determination of fluorescent whitening agents in detergents

A simple, rapid, precise and accurate method for determining the fluorescent whitening agents commonly used in detergents is described. The method is based on simple extraction from the detergent by methanol and on direct injection of the extract, without further purification. The extracted whitening agents were separated using a reversed-phase column (RP-18) and by ion-pair formation. The mobile phase was methanol-water (43 + 57) containing 0.005 M triethylammonium chloride, 0.002 5 M sodium acetate and 0.002 5 M acetic acid. Depending on the type of whitening agent present, the determination can be simplified by using methanol-water (1 + 1) as the mobile phase. Fluorimetric detection makes the method highly sensitive and specific.

Separation of alkanes in Citrus essential oils by on-line coupled high-performance liquid chromatography-high-resolution gas chromatography

The development of gas chromatography (GC) and especially high-resolution GC (HRGC) has made it possible to study essential oils in depth. The high resolving power of capillary columns has allowed separations of the many components present, but the great complexity of the matrices often requires the use of different stationary phases and the use of mass spectrometry (MS) in order to identify the components accurately. Sometimes not even MS is able to identify all the components because similar components give similar fractionation patterns, e.g., as happens with sesquiterpenes’. The recently developed coupling of high-performance liquid chromatography (HPLC) with HRGC has been a great help towards improving our knowledge of the composition of essential oils ‘g3 because it is possible to use simultaneously the high , separating power of HPLC and HRGC to separate the numerous components which are present. The components are first separated by HPLC into relatively small volume of eluate which can be introduced on-line into the gas chromatograph, thus avoiding too much handling of the sample, which can lead to errors. The alkanes in Citrus essential oils have not been studied much up to now4-‘. On-line HPLC-HRGC with concurrent solvent evaporation’-” has been used in our research to study the alkane fraction of cold-pressed Citrus essential oils. The HPLC eluate is injected into the gas chromalograph by using the concurrent solvent evaporation technique. The temperature of the GC column is maintained at a higher value than boiling point of the HPLC eluent, taking into account both the composition of the eluent and the inlet pressure of carrier gas”*r2.

Sb-SnO2-Nanosized-Based Resistive Sensors for NO2 Detection

A study over Sb-promoted tin oxide nanopowders for sensing applications is reported. SnO2 nanopowders pure and promoted with 5 wt% of antimony were prepared by wet chemical methods and widely characterized by TEM, XRD, and XPS techniques. Thick film resistive sensors were fabricated by depositing the synthesized nanopowders by drop-coating on interdigited alumina substrates. The sensing characteristics of the pure SnO2 and Sb-promoted sensors for the monitoring of trace level of NO2 were studied. The response of the sensors to water vapor was also investigated, revealing that Sb acts favorably eliminating the interference of humidity.

Carbonyl sulphide (COS) monitoring on MOS sensors for biomedical applications

Resistive metal-oxide semiconductor (MOS) sensors have been tested in the monitoring of carbonyl sulphide (COS), a biomarker for acute rejection (AR) in lung transplanted patients. COS concentration in the breath of these patients (about 0.5 ppm) is in fact more higher than that found in healthy peoples, making possible the real time diagnosis of this pathology by breath analysis. In2O3-based MOS resistive sensors have been therefore tested at different temperatures and COS concentrations in order to optimize the sensor response and response/recovery time. The ultimate aim of this work is to develop a simple and cost-effective breath test for the acute rejection in lung transplanted patients.

Investigation of Permeation Tubes for Temperature-Compensated Gas-Sensor Calibrators

Ethanol permeation tubes have been proposed for a possible use in temperature-compensated gas-sensor calibrators. Two commercial tubes with a different geometric configuration of the polymeric membrane (wafer- and EL-type) have been tested. First, their permeation characteristics have been evaluated and, subsequently, their performances tested in an apparatus simulating programmed temperature cycles. Both tubes have shown a linear permeation rate in the range of temperature investigated and a low permeation temperature coefficient, with the EL-type tube showing also a very fast response to temperature variation. The integration of this latter tube with a flow-compensation controller has lead to the realization of a temperature-compensated calibrator device, allowing to maintain the ethanol concentration constant at the calibrator outlet by simply modulating the carrier flow through the permeation tube to compensate the temperature fluctuation. Results obtained in the generation of calibrated gas-phase ethanol concentrations, in the range from 1 to 500 ppm, suggest a promising use of these temperature-compensated permeation tubes as calibrators in portable gas-sensor devices