Evaluation of Three Electronic Noses for Detecting Incipient Wood Decay

Tree assessment methodologies, currently used to evaluate the structural stability of individual urban trees, usually involve a visual analysis followed by measurements of the internal soundness of wood using various instruments that are often invasive, expensive, or inadequate for use within the urban environment. Moreover, most conventional instruments do not provide an adequate evaluation of decay that occurs in the root system. The intent of this research was to evaluate the possibility of integrating conventional tools, currently used for assessments of decay in urban trees, with the electronic nose–a new innovative tool used in diverse fields and industries for various applications such as quality control in manufacturing, environmental monitoring, medical diagnoses, and perfumery. Electronic-nose (e-nose) technologies were tested for the capability of detecting differences in volatile organic compounds (VOCs) released by wood decay fungi and wood from healthy and decayed trees. Three e-noses, based on different types of operational technologies and analytical methods, were evaluated independently (not directly compared) to determine the feasibility of detecting incipient decays in artificially-inoculated wood. All three e-nose devices were capable of discriminating between healthy and artificially-inoculated, decayed wood with high levels of precision and confidence. The LibraNose quartz microbalance (QMB) e-nose generally provided higher levels of discrimination of sample unknowns, but not necessarily more accurate or effective detection than the AromaScan A32S conducting polymer and PEN3 metal-oxide (MOS) gas sensor e-noses for identifying and distinguishing woody samples containing different agents of wood decay. However, the conducting polymer e-nose had the greater advantage for identifying unknowns from diverse woody sample types due to the associated software capability of utilizing prior-developed, application-specific reference libraries with aroma pattern-recognition and neural-net training algorithms

A Compact Affordable Electronic Nose Device to Monitor Air Toxic Compounds: A Filter Diagonalization Method Approach

This paper introduces a compact, affordable electronic nose (e-nose) device which aim is to detect volatile compounds that could affect human health, such as carbon monoxide, combustible gas, hydrogen, methane, and smoke, among others. Such artificial olfaction device consists of an array of six metal oxide semiconductor (MOS) sensors and a computer-based system for data acquisition, processing, and visualization. This study further proposes the use of the Filter Diagonalization Method (FDM) to extract the spectral contents of the signals obtained from the sensors. Preliminary results show that the prototype is functional and that the FDM approach is suitable for a later classification stage. Example deployment scenarios of the proposed enose include indoor facilities (buildings and warehouses), compromised air quality places (mines and sanitary landfills), public transportation, mobile robots, and wireless sensor networks

Potential Applications and Limitations of Electronic Nose Devices for Plant Disease Diagnosis

Electronic nose technology has recently been applied to the detection of several plant diseases and pests, with promising results. However, in spite of its numerous advantages, including operational simplicity, non-destructivity, and bulk sampling, drawbacks include a low sensitivity and specificity in comparison with microbiological and molecular methods. A critical review of the use of an electronic nose for plant disease diagnosis and pest detection is presented, describing the instrumental and procedural advances of sensorial analysis, for the improvement of discrimination between healthy and infected or infested plants. In conclusion, the use of electronic nose technology is suggested to assist, direct, and optimise traditionally adopted diagnostic technique

Applications and Advances in Electronic-Nose Technologies

Electronic-nose devices have received considerable attention in the field of sensor technology during the past twenty years, largely due to the discovery of numerous applications derived from research in diverse fields of applied sciences. Recent applications of electronic nose technologies have come through advances in sensor design, material improvements, software innovations and progress in microcircuitry design and systems integration. The invention of many new e-nose sensor types and arrays, based on different detection principles and mechanisms, is closely correlated with the expansion of new applications. Electronic noses have provided a plethora of benefits to a variety of commercial industries, including the agricultural, biomedical, cosmetics, environmental, food, manufacturing, military, pharmaceutical, regulatory, and various scientific research fields. Advances have improved product attributes, uniformity, and consistency as a result of increases in quality control capabilities afforded by electronic-nose monitoring of all phases of industrial manufacturing processes. This paper is a review of the major electronic-nose technologies, developed since this specialized field was born and became prominent in the mid 1980s, and a summarization of some of the more important and useful applications that have been of greatest benefit to man

Assessment of Volatile Metabolites for In Situ Detection of Fungal Decay of Wood

Although incipient fungal decay of wood may be difficult to detect early, it causes a significant decrease in wood strength. Developing a reliable method of decay identifica-tion to overcome wood replacement costs by non-destructive methods is necessary. This study investigates a possibility of identifying fungal volatile organic compounds (VOCs) as means of fungal detection using solid phase micro-extraction (SPME) coupled with gas chromatography–mass spectrometry (GC-MS). Volatile emissions from two brown rot (Gloeophyllum trabeum and Postia pla-centa) and two white rot (Trametes versicolor and Irpex lacteus) fungi on pine and aspen and their profiles related to wood mechanical strength and mass loss were investigated over 12 weeks. Principal component analysis of VOCs spectra differentiated volatiles from decayed and sound wood. Volatiles from two fungal species revealed distinct pat-terns of early and late degradation stages. SPME combined with GC-MS showed promissing results for non-destructive identification of incipient decay in wood struc-tures

Reliable e-nose for air toxicity monitoring by filter diagonalization method

This paper introduces a compact, affordable electronic nose (e-nose) device devoted to detect the presence of toxic compounds that could affect human health, such as carbon monoxide, combustible gas, hydrogen, methane, and smoke, among others. Such artificial olfaction device consists of an array of six metal oxide semiconductor (MOS) sensors and a computer-based information system for signal acquisition, processing, and visualization. This study further proposes the use of the filter diagonalization method (FDM) to extract the spectral contents of the signals obtained from the sensors. Preliminary results show that the prototype is functional and that the FDM approach is suitable for a later classification stage. Example deployment scenarios of the proposed e-nose include indoor facilities (buildings and warehouses), compromised air quality places (mines and sanitary landfills), public transportation, mobile robots, and wireless sensor networks

Bulk and Surface Acoustic Wave Sensor Arrays for Multi-Analyte Detection: A Review

Bulk acoustic wave (BAW) and surface acoustic wave (SAW) sensor devices have successfully been used in a wide variety of gas sensing, liquid sensing, and biosensing applications. Devices include BAW sensors using thickness shear modes and SAW sensors using Rayleigh waves or horizontally polarized shear waves (HPSWs). Analyte specificity and selectivity of the sensors are determined by the sensor coatings. If a group of analytes is to be detected or if only selective coatings (i.e., coatings responding to more than one analyte) are available, the use of multi-sensor arrays is advantageous, as the evaluation of the resulting signal patterns allows qualitative and quantitative characterization of the sample. Virtual sensor arrays utilize only one sensor but combine itwith enhanced signal evaluation methods or preceding sample separation, which results in similar results as obtained with multi-sensor arrays. Both array types have shown to be promising with regard to system integration and low costs. This review discusses principles and design considerations for acoustic multi-sensor and virtual sensor arrays and outlines the use of these arrays in multi-analyte detection applications, focusing mainly on developments of the past decade

Advances in Electronic-Nose Technologies Developed for Biomedical Applications

The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The purposes of this review are to present a comprehensive analysis of past and recent biomedical research findings and developments of electronic-nose sensor technologies, and to identify current and future potential e-nose applications that will continue to advance the effectiveness and efficiency of biomedical treatments and healthcare services for many years. An abundance of electronic-nose applications has been developed for a variety of healthcare sectors including diagnostics, immunology, pathology, patient recovery, pharmacology, physical therapy, physiology, preventative medicine, remote healthcare, and wound and graft healing. Specific biomedical e-nose applications range from uses in biochemical testing, blood-compatibility evaluations, disease diagnoses, and drug delivery to monitoring of metabolic levels, organ dysfunctions, and patient conditions through telemedicine. This paper summarizes the major electronic-nose technologies developed for healthcare and biomedical applications since the late 1980s when electronic aroma detection technologies were first recognized to be potentially useful in providing effective solutions to problems in the healthcare industry

E-Tongues/Noses Based on Conducting Polymers and Composite Materials: Expanding the Possibilities in Complex Analytical Sensing

Conducting polymers (CPs) are extensively studied due to their high versatility and electrical properties, as well as their high environmental stability. Based on the above, their applications as electronic devices are promoted and constitute an interesting matter of research. This review summa- rizes their application in common electronic devices and their implementation in electronic tongues and noses systems (E-tongues and E-noses, respectively). The monitoring of diverse factors with these devices by multivariate calibration methods for different applications is also included. Lastly, a critical discussion about the enclosed analytical potential of several conducting polymer-based devices in electronic systems reported in literature will be offered

Development of a Basic Biosensor System for Wood Degradation using Volatile Organic Compounds

Die Prüfung von Holz und ein Test seiner Beständigkeit gegen Mikroorganismen wie Pilze spielen eine wichtige Rolle in der Forstwirtschaft und der holzverarbeitenden Industrie. Um solche Prüfungen zu erleichtern und präzise Bewertungen zu ermöglichen, ist eine effiziente Testmethode erforderlich. Flüchtige organische Verbindungen (volatile organic compounds VOCs), die vom Holzsubstrat und vom pilzlichen Metabolismus erzeugt werden, sind Marker für den Zustand des Holzes, d.h. sie zeigen Art und Stadium einer Pilzinfektion an. Insektenantennen, die für ihre hohe Sensitivität und Selektivität in der Duftwahrnehmung bekannt sind, stellen eine alternative Methode zur Holzprüfung dar. Ein Biosensor auf der Basis intakter Insektenantennen ermöglicht es, vom Holz freigesetzte VOCs mit hoher Selektivität nachzuweisen. Diese Methode kann eine Ergänzung zu den traditionellen Prüfverfahren darstellen und bietet einen hohen Probendurchsatz sowie ein zerstörungsfreies Verfahren. Als Beginn dieser Arbeit wurden die VOCs verschiedener Proben mit Gaschromatographie-Massenspektroskopie untersucht. Zuerst wurden die VOCs von Buchenholz (Fagus sylvatica) analysiert, das mit drei holzzersetzenden Pilzen (Trametes versicolor, Poria placenta und Gloeophyllum trabeum) infiziert war. Diese Pilze werden häufig verwendet, um die Beständigkeit von Holz gegen Mikroorganismen zu testen. Die vom pilzinfizierten Buchenholz freigesetzten VOCs zeigten artspezifische Muster. Die Volatile lassen sich gruppieren in Stoffe mit fünf bis acht Kohlenstoffen (C5-C8) sowie Terpenoide. 1-Octen-3-ol, 3-Octanon und 3-Octanol (C8-Verbindungen) waren allgemein in allen Proben enthalten, während Terpenoide artspezifisch auftraten. α- und β-Barbaten waren charakteristisch für eine Infektion mit T. versicolor, Protuillud-6-en war charakteristisch für G. trabeum und Daucen war charakteristisch für P. placenta. Als Zweites wurden VOCs identifiziert, die von verschiedenen Stadien von Trametes gibbosa mit schwacher bis vollständiger Kolonisierung durch den Käfer Cis boleti freigesetzt wurden. Die schwach besiedelten Fruchtkörper setzten den typischen Pilzduftstoff 1-Octen-3-ol in fast zwanzigfach höherer Menge frei als vollständig besiedelte Fruchtkörper. Als Drittes wurden die VOCs untersucht, die während der Fruchtkörperentwicklung vom Stadium des Myceliums bis zur Autolyse von Coprinopsis cinerea freigesetzt werden. Die VOC-Muster von C. cinerea änderten sich spezifisch mit den Entwicklungsstadien. 1-Octen-3-ol und 3-Octanon zeigten während der Bildung der Primodia eine starke Freisetzung, die in späteren Stadien abnahm. Die Terpenoide β-Himachalen und Cuparen wurden während Wachstum und Reifung des Stängels von C. cinerea drastisch erhöht. Zum Abschluss wurden die autolytischen Fruchtkörper der Tintlinge Coprinus comatus, Coprinopsis atramentaria und C. cinerea untersucht. Als zusätzliche Stoffe wurden hier stickstoff- und schwefelhaltige Verbindungen freigesetzt. Der fungivore Käfer Cis boleti (Coloptera: Ciidae) und die pilzassoziierte Fliege Suillia mikii (Diptera: Heleomizydae) wurden ausgewählt, um ihre geruchliche Wahrnehmung zu untersuchen, da ihre Lebenszyklen einen starken Bezug zu Pilzen haben. Zum Beispiel kolonisiert C. boleti vorzugsweise Pilze der Gattung Trametes und S. mikii landen gezielt auf Tintlingen in spezifischen Entwicklungsstadien. Gaschromatographie-Massenspektrometrie mit paralleler elektroantennographischer Detektion (EAD) wurde eingesetzt, um zu demonstrieren, dass beide Insektenarten in der Lage sind, den typischen Pilzgeruchsstoff 1-Octen-3-ol mit hoher Selektivität und Sensitivität nachzuweisen. Zusätzlich zeigten Verhaltenstests, dass C. boleti in der Lage ist, die Enantiomere von 1-Octen-3-ol zu unterscheiden, wobei weibliche Käfer signifikant stärker vom (S)-(+)-Enantiomer angelockt wurden und dies schon bei geringeren Konzentrationen als die männlichen Käfer. Die Fliege S. mikii reagierte in EAD-Tests reproduzierbar auf die VOCs 1-Undecene, 2-Butanon und Dimethyl-Trisulfid, die bei der Autolyse der Fruchtkörper von Tintlingen freigesetzt werden. Die Antennen von C. boleti detektierten den typischen Pilzgeruch 1-Octen-3-ol mit hoher Selektivität und Sensitivität bis zu einer Konzentration von 5 ng ml-1 in Luft. Die Lebensdauer der Antennen betrug bis zu ein Tag. Als grundlegender Test wurden Antennen von C. boleti als Biokomponenten eines Biosensorsystems benutzt, um Buchenholzproben mit Infektion durch T. versicolor zu untersuchen. Dazu diente ein Biosensorsystem, das auf der Überlagerungsmethode in Verbindung mit einem Rekalibrierungssystem basiert. In dieser Konfiguration lieferten die Antennen von C. boleti reproduzierbare Reaktionen auf die pilzlichen Markerstoffe, die von pilzinfiziertem Buchenholz freigesetzt werden. Zusammengefasst führen diese Ergebnisse zu einer aussichtsreichen Möglichkeit, einen Biosensor auf Basis von intakten Antennen als hoch empfindliche und selektive Testmethode für die Holzbeständigkeit gegen zersetzende Pilze zu entwickeln