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Es wird ein Sensorsystem (HUMItrace III) zur Spurenfeuchtebestimmung in der Prozessmesstechnik vorgestellt. Die Bestimmung der Spurenfeuchte erfolgt mit neuentwickelten planaren Sensoren (HUMItrace-Sensoren) nach dem coulometrischen Messprinzip im Frostpunkttemperaturbereich von -80 °C bis -30 °C mit der Kalibriereinrichtung THG11 durch Mischen von trockenen und befeuchteten Teilgasströmen kalibriert. Die Gasfeuchte von Luft kann in diesem Bereich mit den HUMItrace-Sensoren mit einer erweiterten Unsicherheit von 2 K bestimmt werden. Die Sensoren können aber auch zur Gasfeuchtemessung in Wasserstoff, Stickstoff und Distickstoffmonoxid eingesetzt werden. Eine weitere Kalibriereinrichtung, THG-P12, generiert Prüfgase nach der Permeationsmethode; sie kann in das HUMItrace III Sensorsystem implementiert und zur vor-Ort-Kalibrierung der HUMItrace-Sensoren nach dem Standardadditionsverfahren genutzt werden.
A new planar sensor element for continuous coulometric trace humidity measurements in industrial gases has been developed. In order to ensure precise measurements a calibration facility including a precision dew point hygrometer as a reference device was developed. The sensor can measure the humidity in the frost point temperature range of -20 °C to -80 °C and has an expanded uncertainty of 2 K, a fast reaction time and a settling time of the entire system from 15 to 30 min.
Spices have an important impact on daily aliment. Changes of their quality resulting in far reaching consequences in different foodstuffs and imply financial losing and even health hazard. In this study it is demonstrated that application of two different portable multi gas sensors (electronic nose and ion mobility spectrometer) supported by multivariate data analysis can contribute to ensure quality control of spice mixtures and to find out product adulteration. Headspace above spice mixtures for sausages and saveloy and product counterfeitings was investigated by a metal oxide based electronic nose (e-nose of KAMINA-type). Linear discriminant analysis (LDA) of sensor resistivity data was performed for differentiation. Simultaneously an ion mobility spectrometer (IMS) was coupled to the emission chamber for detection of gaseous components above spice mixtures. The measured spectra show differences between the two spice mixtures and were discussed using a principal component analysis (PCA). The two multigas sensors permit discrimination between the types of spice mixtures and can indicate product adulteration. Additionally, a headspace gas analysis by gas chromatography was performed to identify the main volatile components and to prove the chemical basis for the observed differences of the multi gas sensors.
An experimental investigation has been carried out to characterize and discriminate seven saffron samples and to verify their declared geographical origin using a voltammetric electronic tongue (VE-tongue). The ability of multivariable analysis methods such as Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA) to classify the saffron samples according to their geographical origin have been investigated. A good discrimination has reached using PCA and HCA in the VE-tongue characterization case. Furthermore, cross validation and Partial Least Square (PLS) techniques were applied in order to build suitable management and prediction models for the determination of safranal concentration in saffron samples based on SPME-GC-MS and UV-Vis Spectrophotometry. The obtained results reveals that some relationships were established between the VE-tongue signal, SPMEGC-MS and UV-Vis spectrophotometry methods to predict safranal concentration levels in saffron samples by using the PLS model. In the light of these results, we can say that the proposed electronic system offer a fast, simple and efficient tool to recognize the declared geographical origin of the saffron samples.
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.
Application of electronic nose and ion mobility spectrometer to quality control of spice mixtures
(2009)
Traces of microbial volatile organic compounds (MVOCs) in air can indicate the presence of growth of moulds in the indoor environment. Ion-mobility spectrometry is a very promising method for detection of these MVOCs, because of its high sensitivity. For development of an in-situ method for detection of MVOCs, a portable ion-mobility spectrometer (IMS) was used and test gases of 14 MVOCs and their respective mixtures were investigated. IMS spectra were recorded as a function of concentration of MVOCs in air. Drift time and mobility of reactant ions formed in positive polarity mode were determined and correlated with the mass-to-charge ratio (m/z) of the MVOCs investigated. The estimated detection limit has a specific value for each MVOC and is in the range 3 to 96 µg m-3 (1 to 52 ppbV). Indoor trials show that IMS can indicate hidden mould growth.
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.
Technische Richtlinien enthalten Empfehlungen sowie Anforderungen zum Stand der Technik zur Aufstellung von Bewertungskriterien und Behandlung wissenschaftlich-technischer Fragen. Sie fördern den Erfahrungsaustausch und Technologietransfer zwischen Entwicklern und Anwendern.
In unserem Beitrag stellen wir die Richtlinie VDI/VDE 3518 vor. Diese Richtlinienreihe definiert Begriffe, beschreibt den Aufbau und klassifiziert Multigassensoren (Blatt 1), befasst sich mit den Anforderungen für das Unterscheiden, Erkennen und mengenmäßige Bestimmen von Gemischen gasförmiger Stoffe und die Prüfung von Multigassensoren (Blatt 2) und gibt Anleitung für geruchsbezogene Messungen mit „Elektronischen Nasen“ (Blatt 3). Multigassensoren können als elektronische Nasen in Anlehnung an den biologischen Geruchssinn zur Wahrnehmung und Charakterisierung von Gerüchen eingesetzt werden. Die Spezifik von Multigassensoren besteht darin, dass durch die Wahl und Betriebsweise der Sensoren eine Vielzahl von geeigneten Messsignalen erzeugt werden, aus denen mit mathematischen Verfahren die für die Anwendung gewünschten Informationen extrahiert werden. Dazu ist ein Training der Messeinrichtung mit Proben bekannter Eigenschaften notwendig.
Diese Richtlinie soll Herstellern, Anbietern und Nutzern als ein Leitfaden Informationen und Erläuterungen für die korrekte und sichere Arbeit mit Multigassensoren liefern. Sie soll Prüflaboratorien und Anwendern helfen, bei der Beurteilung von Qualitätsmerkmalen einheitlich vorzugehen und dafür gemeinsame Randbedingungen anzugeben