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This paper presents the VISTA (Volatile In Situ Thermogravimetry Analyser) instrument, conceived to perform planetary in-situ measurements. VISTA can detect and quantify the presence of volatile compounds of astrobiological interest, such as water and organics, in planetary samples. These measurements can be particularly relevant when performed on primitive asteroids or comets, or on targets of potential astrobiological interest such as Mars or Jupiter's satellite Europa. VISTA is based on a micro-thermogravimetry technique, widely used in different environments to study absorption and sublimation processes. The instrument core is a piezoelectric crystal microbalance, whose frequency variations are affected by variations of the mass of the deposited sample, due to chemical processes such as sublimation, condensation or absorption/desorption. The low mass (i.e. 40 g), the low volume (less than 10 cm(3)) and the low power (less than 1 W) required makes this kind of instrument very suitable for space missions. This paper discusses the planetary applications of VISTA, and shows the calibration operations performed on the breadboard, as well as the performance tests which demonstrate the capability of the breadboard to characterize volatile compounds of planetary interests.

Benzene, toluene and xylene (BTX) are an important part of the volatile organic compounds (VOCs) to be detected and monitored in the air, due to their toxicity towards human health. One of the most reliable technique used in BTX detection is gas chromatography (GC), which presents a high sensitivity. On the other hand, it has important drawbacks, such as high costs, the need for qualified personnel and frequent maintenance. To overcome these drawbacks, this work reports the development of a low cost and portable BTX gas detection system based on a mini chromatographic cartridge, a photo ionization detector (PID), a simple control unit (based on Arduino architecture) and a mini pump. In order to separate the BTX components, we propose the use of a cartridge 80 mm in length, composed of several commercial chromatographic column sections. To test the system performances, we have injected different amounts (from about 0.3 to 5.3 µg) of benzene, toluene and xylene and two of the most frequent possible interferents (ethanol, acetone). Experimental results have shown different retention time values (i.e., 25 ± 0.5 s, 51 ± 1.2 s and 117 ± 4 s, respectively) for benzene, toluene and xylene. [ABSTRACT FROM AUTHOR]

Structural and functional properties of polymer composites based on carbon nanomaterials are so attractive that they have become a big challenge in chemical sensors investigation. In the present study, a thin nanofibrous layer, comprising two insulating polymers (polystyrene (PS) and polyhydroxibutyrate (PHB)), a known percentage of nanofillers of mesoporous graphitized carbon (MGC) and a free-base tetraphenylporphyrin, was deposited onto an Interdigitated Electrode (IDE) by electrospinning technology. The potentials of the working temperature to drive both the sensitivity and the selectivity of the chemical sensor were studied and described. The effects of the porphyrin combination with the composite graphene–polymer system appeared evident when nanofibrous layers, with and without porphyrin, were compared for their morphology and electrical and sensing parameters. Porphyrin fibers appeared smoother and thinner and were more resistive at lower temperature, but became much more conductive when temperature increased to 60–70 °C. Both adsorption and diffusion of chemicals seemed ruled by porphyrin according its combination inside the composite fiber, since the response rates dramatically increased (toluene and acetic acid). Finally, the opposite effect of the working temperature on the sensitivity of the porphyrin-doped fibers (i.e., increasing) and the porphyrin-free fibers (i.e., decreasing) seemed further confirmation of the key role of such a macromolecule in the VOC (volatile organic compound) adsorption. [ABSTRACT FROM AUTHOR]

Abstract: In this work the ability to perform desorption studies by using a micro-thermogravimetric device is demonstrated. The instrument consists of an oscillating quartz crystal microbalance with an integrated micro-heater that might turn out to be extremely useful in the study of the desorption of volatile compounds from refractory materials. The experiment here discussed has been performed by studying the release of adsorbed water from clay. Clay has been principally chosen because it is a material known for its ability to desorb and subsequently re-adsorb water at low temperatures and it might be considered a test mineral for a large number of applications, from first guess analysis of agricultural soil to quick inspection of materials of planetological interest (e.g., asteroid regolith). Results show that the device can be in stable operative conditions at 100°C with 0.5W of power supplied, allowing to measure the amount of desorbed water. In particular, as expected, it has been possible to assess that the desorbed water amount depends upon the working temperature, being less than 3wt.% at 70°C and about 5wt.% at 90°C. [Copyright &y& Elsevier]

In this work we report the results concerning the integration of a thin layer of an organic polymer (pentacene) on a quartz crystal microbalance (QCM) used for pollutant detection at room temperature. Volatile organic compounds (VOC) are one of the major air pollutants. They are directly involved in the photochemistry of the ozone layer and can affect human health. Exposure to VOC may happen in indoor or outdoor environments, both for short or longer period of time in domestic or working conditions. Among VOCs, mono aromatic compounds such as benzene, toluene or xylenes (often referred as BTX) have carcinogenic, narcotic and neurotoxic properties. Thin films of pentacene were obtained by thermal physical vapor deposition both on transducers and silicon substrates. Structural and morphological characterizations by FTIR and AFM analysis confirm analogy between layered material before and after BTX exposition. QCM was chosen as a transducer due to the kind of interactions involved between material and the target gases. The device was exposed to BTX both in dry and wet conditions. The measurements results where compared also with those collected during the exposure toward humidity and ethanol. A clear discrimination between the different analytes was found. [ABSTRACT FROM AUTHOR]