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The detection of the aroma and flavour volatile compounds of spices is key in product quality control. Accordingly, it is necessary to develop new electronic sensing systems for food adulteration control and authenticity assessment for protecting customer's health.
In this work, the capability of the E-nose and VE-tongue in combination with SPME-GC-MS to correctly discriminate between several cumin samples of different geographical origins and to detect their adulteration, by using unsupervised and supervised chemometric tools, was evaluated. Regarding the aroma profile, eleven volatile compounds were characterized by SPME-GC-MS; all of them were found in cumin powder while only eight are found in cumin seeds. The main volatile compounds detected were b-pinene, m-cymene, g-terpinene, cuminaldehyde and cuminic alcohol, in different proportions depending on the cumin sample form (seed or powder). In summary, the results obtained are sufficiently encouraging as a starting point for the development of new electronic sensing systems with more improvement in the reliability of the sensor's performance as well as chemometric tools in order to deal with a complex dataset.
H2Sense - Cost-effective and reliable Hydrogen Sensors for Facilitating the Safe Use of Hydrogen
(2016)
The H2SENSE (Cost-effective and reliable hydrogen sensors for facilitating the safe use of hydrogen) project promoted hydrogen primarily, but not exclusively, for its use as an alternative fuel. It brought together different stakeholders including sensor manufacturers, end-users, certification bodies and independent evaluators to ensure the optimum use of low-cost and reliable hydrogen sensors.
Project partners analysed sensor performance in real-life applications in industrial environments and identified increased requirements for sensors and for regulations, codes and standards. H2SENSE also facilitated the safe use and implementation of hydrogen as an alternative fuel by ensuring the correct use of effective hydrogen detection devices.
European scientists worked together with colleagues from the National Renewable Energy Laboratory (NREL) in Colorado, USA. They pooled their knowledge of developments in hydrogen sensor technology as well as deployment and commercialisation strategies. These benefits will be continued through trans-Atlantic inter-laboratory sensor testing programmes in which EU and US laboratories perform complementary tests and exchange results.
The chapter describes the application of electronic noses (multigas sensors) for the quality control of spices and spice mixtures. Electronic noses were successfully applied for headspace analysis of spices. It was demonstrated in many investigations that electronic noses can contribute to the characterization of spices and spice mixtures in order to distinguish spices and spice mixtures, differentiate by origin, growth seasons,and processing,indicate adulteration from original, detect mold infestation. Electronic noses can be used as a fast screening method to provide information about the product quality. However, it needs samples and methods for reference, careful training, and complex calibration to consider influencing and disturbing effects as well as the possible limitations of the instrumentation. The correlation to classical chemical analysis methods is always advisable. Machined olfaction methods are capable to support the sensory analysis; however, they cannot yet substitute them.
A series of Mg₁₋ₓZnₓTiO₃, x = 0–0.5 (MZT0–MZT0.5) ceramics was synthesised and characterised. The dielectric properties of the samples in the frequency range of
1 Hz – 7.7 GHz were explored using three different methods:
a contacting electrode method, a parallel-plate method and a perturbed resonator method. The electrical properties in the space charge and dipolar polarisation frequency ranges are discussed in relation to the phase composition and microstructure data. Differences in the zinc Substitution divided the dielectrics into two groups, namely MZT0-MZT0.2 and MZT0.3–MZT0.5, each with different amount of a main Mg₁₋ₓZnₓTiO₃ solid solution phase and a secondary solid solution phase. Zinc substitution promoted the density of the ceramics, improved the purity of the main phase and increased the permittivity for frequencies up to 10⁸ Hz, but reduced the permittivity in the microwave range. In the MZT0.3–MZT0.5 samples, for frequencies less than 1 MHz the quality (Q x ƒ) factors were lower and log σ ₐ.c, the AC conductivity, was higher than for the MZT0–MZT0.2 samples. Above 10 MHz, the (Q x ƒ) factors and log σ ₐ.c of the two groups were similar.
A portable device for calibration of trace humidity sensors and an adopted calibration procedure have been developed. The calibration device is based on humidity generation by permeating water through polymeric membrane tubes. Water vapour transmission rates for various polymers were experimentally determined in order to select the most suitable polymeric material. The developed trace humidity generator consists of a gas-flow polymeric hose immersed in a water reservoir thermostated by a sensorcontrolled heater. Mole fractions of water vapour between 1 µmol/ molˉ¹ and 350 µmol/molˉ¹ (equivalent to frost-point temperatures from -76 °C to -31 °C) were generated by varying either the operating temperature or gas flow. The operating temperature can be varied from 20 °C to 60 °C and kept stable within 0.1 K. Uncertainty analysis indicated that the trace humidity generator produces gas flows of constant humidity amounts with a relative expanded uncertainty less than 3.4% (k = 2) of the generated value.
This book is on sensors which are regularly deployed in technologies and processes related to hydrogen production, storage, distribution, and use. Not all types of sensors are equally suitable for specific hydrogen applications. The information in this book is intended to help the reader understand the basics of sensors, sensing technologies, sensor applications, and to provide guidelines for choosing the right sensors and the use of them correctly. Correct deployment of appropriate sensors demands knowledge of the sensing principle and of the physical or chemical quantities being measured. Because of the properties of hydrogen, the potential for its vastly increased use in a future low-carbon economy and possible hazards associated with its use, special attention is paid to hydrogen sensors. This book will not focus on the details of the hydrogen technologies nor on the many safety-related aspects of these technologies. Many books are already available on these topics. Instead the detection principle of hydrogen sensors and other sensor types used, in the dynamic and rapidly developing field of hydrogen technologies, are treated in detail in this book.
In the first chapter a brief overview is presented on basic hydrogen properties and particularly on those properties which are most relevant for safety and for sensing. To illustrate the extensive field of contemporary applications and the exciting possibilities for near future sensor applications, existing and emerging markets using large quantities of hydrogen are mentioned. The role of sensors as devices for monitoring and control of processes and as safety monitoring devices is outlined.
The second chapter gives an introduction to sensing technology and provides the Reader with relevant information pertaining to sensor definitions and classification, sensor metrics, and performance arameters, in addition to background information on sensor preparation technologies and techniques. While there are many books available which provide more exhaustive information on each of these topics, e.g., the level of detail provided in this chapter is sufficient to appreciate the salient features of sensing and sensing Technology which are central to hydrogen safety and monitoring of relevant applications.
Chapter 3 provides a comprehensive overview of emerging and commercially available hydrogen sensors, an explanation of their sensing principle, and important aspects of their performance. A comprehensive and up-to-date account of the theory (physical or chemical principles), design, and practical implementations of hydrogen sensors for use in hydrogen related applications is presented.
Similar information on chemical sensors for other gases, such as oxygen and trace components, which are also highly important in hydrogen technologies because of potential hazards to human health, process safety or facility performance, is provided in Chapter 4.
In Chapter 5 descriptions of physical sensors for temperature, pressure, gas flow, and fire indication, which are also germane for the safe use of hydrogen, are provided.
Standards, codes, and regulatory documents, which provide practical advice and legislative requirements regarding sensor deployment and performance, are described in Chapter 6. This chapter also makes reference to the main procedures for sensor testing in gas Standards including precise analytical methods and reference methods. The chapter concludes with a discussion on sensor selection and some installation guidelines are provided.
In Chapter 7 traditional and emerging processes and technologies involving hydrogen are described. The application of sensors in processes for the production of hydrogen, hydrogen storage, distribution, and the use of hydrogen in stationary and mobile fuel cells is discussed. Furthermore, the use of hydrogen as a coolant and chemical reagent (medium) in various processes is described. The exploitation of sensors for replacing traditional analytical instrumentation is also discussed. Finally supplementary information is provided on hydrogen properties, measuring quantities, and sensor parameters.