Air & Waste Management Association (A&WMA)

Development of a novel odor measurement system using gas chromatography

This paper describes a novel odor measurement system for creating arrays of virtual chemical sensors with nonoverlapping responses using ultrahigh-speed gas chromatography with a surface acoustic wave sensor (GC/SAW). This GC/SAW system provides high-resolution twodimensional olfactory images for easy recognition of many complex odors. Separation and quantification of the individual chemicals within an odor is performed in seconds. Using a solid-state mass-sensitive detector, picogram sensitivity, universal nonpolar selectivity, and electronically variable sensitivity are achieved. An integrated vapor preconcentrator coupled with the electronically variable detector allows the system to measure vapor concentrations spanning 6 or more orders of magnitude. The system attributes of high speed, accuracy, and precision provide a cost-effective and complimentary tool for traditional sensory evaluations.


Odor or malodor, which refers to unpleasant smells, is nowadays considered an important contributor to environmental
pollution. The public is keenly aware of odor pollution events and they often act as first indicators of air quality problems in their community. Resolution of odor pollution is often difficult because the behavioral responses to odor vary from person to person, and also because it is generally difficult to quantify the presence of odor-causing chemicals. Although the human nose is used as a way to quantify odor impacts, the quantification of odor-causing compounds responsible for causing odor complaints is required to solve odor problems. Typically, these odorous compounds are present in small
quantities and hence are difficult to quantify. Conventional technologies require large sample collection over a long period of time and extensive sample preconcentration before any analysis is done using instruments such as gas chromatographs and mass spectrometers. Fortunately, there have been recent advances in measurement technologies such as the invention of electronic noses. Conventional electronic noses (eNoses) produce a recognizable response pattern using an array of dissimilar but not specific chemical sensors. Electronic noses have interested developers of neural networks and artificial intelligence algorithms for some time, yet physical sensors have limited performance because of overlapping responses and
physical instability. eNoses using physical sensor arrays cannot separate the chemicals within vapors and hence cannot quantify the chemistry of aromas. This paper describes a new type of electronic nose, based upon high-speed gas chromatography with surface acoustic wave sensor (GC/SAW). This simulates an almost unlimited number of specific virtual chemical sensors and produces olfactory images based upon aroma chemistry. This research work describes analytical measurements of odors conducted in near real time with partsper- billion sensitivity.

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