New method of vaporising volatile organics for gas tests

Bodenhöfer, K.; Hierlemann, Andreas; Schlunk, Rainer; Göpel, Wolfgang

doi:10.1016/s0925-4005(97)00319-5

Cited by 20 publications

(13 citation statements)

References 6 publications

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“…The analyte vapors were generated from specifically developed temperature-controlled ( T = 223 to 293 K) vaporizers using synthetic air as carrier gas and then diluted as desired using computer-driven mass-flow controllers. The internal volume of these vaporizers, which distribute the liquid over a large-area, packed-bed type support to maximize surface-to-volume ratio, was dramatically smaller than that of typical gas-washing bottles (“bubblers”) . By using these vaporizers, the noise in the sensor signals caused by concentration fluctuations or aerosol formation of the liquid analytes is reduced, and the reproducibility of the adjusted gas-phase concentrations is significantly enhanced.…”

Section: Methodsmentioning

confidence: 99%

Transient Signal Analysis Using Complementary Metal Oxide Semiconductor Capacitive Chemical Microsensors

2005

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This work explores the possibility to discriminate analytes based on their nonequilibrium signals in polymer-coated capacitive chemical microsensors. The analyte uptake in the chemically sensitive polymer layers of 3-7-microm thickness has been analyzed using a diffusion model and the dynamic sensor response data. The shapes of the response profiles have been calculated analytically. Despite the simplifications in the model, the observed transient signal profiles could be described accurately. Comparison of the measured diffusion coefficients (on the order of 10(-12) m2/s) with literature values measured at similar concentration levels showed good agreement. Concentration-independent diffusion coefficients for several analyte/polymer combinations (poly(etherurethane)/all analytes; poly(epichlorohydrin)/alcohols) as well as slightly concentration-dependent diffusion coefficients (poly(epichlorohydrin)/toluene or ethyl cellulose/toluene) have been found in the investigated concentration range of tens to hundreds of pascals gas-phase partial pressure. The diffusion times of water and the first aliphatic monohydric alcohols in the polymers are strongly correlated to their molecular size. The discrimination of these substances based on dynamic sensor data of a single sensor could be demonstrated. In particular, the analysis of mixtures of analytes with similar chemical behavior (water/ethanol or methanol/ethanol) by means of analyzing the response profile of single-exposure steps or by applying a series of decreasingly long alternating target gas exposure and carrier gas exposure steps has been performed.

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Section: Methodsmentioning

confidence: 99%

Transient Signal Analysis Using Complementary Metal Oxide Semiconductor Capacitive Chemical Microsensors

2005

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“…Vapors were generated from specially developed temperature-controlled ( T = 283−298 K) vaporizers using synthetic air as carrier gas and then diluted as desired using computer-driven mass-flow controllers. The internal volume of these vaporizers, which distribute the liquid over a large-area packed-bed type support to maximize the surface to volume ratio, was dramatically smaller than that of typical gas-washing bottles (“bubblers”); hence very small quantities of expensive chiral analytes could be released at constant concentration …”

Section: Methodsmentioning

confidence: 99%

Effective Use of Molecular Recognition in Gas Sensing: Results from Acoustic Wave and in Situ FT-IR Measurements

et al. 1999

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“…The analyte vapors were generated from specifically developed temperature-controlled ( T = 223−293 K) vaporizers using synthetic air as a carrier gas and then diluted as desired using computer-driven mass flow controllers. The vapor-phase concentrations at the respective temperatures were calculated following the Antoine equation .…”

Section: Methodsmentioning

confidence: 99%

Detection and Discrimination Capabilities of a Multitransducer Single-Chip Gas Sensor System

2006

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The performance of a single-chip, three-transducer, complementary metal oxide semiconductor gas sensor microsystem has been thoroughly evaluated. The monolithic gas sensor system includes three polymer-coated transducers, a mass-sensitive cantilever, a thermoelectric calorimetric sensor, and an interdigitated capacitive sensor that are integrated along with all electronic circuits needed to operate these sensors. The system additionally includes a temperature sensor and a serial interface unit so that it can be directly connected to, for example, a microcontroller. Several multitransducer chips have been coated with various partially selective polymers and then have been exposed to different volatile organic compounds. The sensitivities of the three different polymer-coated transducers to defined sets of gaseous analytes have been determined. The obtained sensitivity values have then been normalized with regard to the partition coefficients of the respective analyte/polymer combination to reveal the transducer-specific effects. The results of this investigation show that the three different transducers respond to fundamentally different molecular properties, such as the analyte molecular mass (mass-sensitive), its dielectric coefficient (capacitive), and its sorption heat (calorimetric) so that correlations between the determined sensitivity values and the different molecular properties of the absorbed analytes could be established. The information as provided by the system, hence, represents a body of orthogonal data that can serve as input to appropriate signal processing and pattern recognition techniques to address issues such as the quantification of analytes in mixtures.

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New method of vaporising volatile organics for gas tests

Cited by 20 publications

References 6 publications

Transient Signal Analysis Using Complementary Metal Oxide Semiconductor Capacitive Chemical Microsensors

Transient Signal Analysis Using Complementary Metal Oxide Semiconductor Capacitive Chemical Microsensors

Effective Use of Molecular Recognition in Gas Sensing: Results from Acoustic Wave and in Situ FT-IR Measurements

Detection and Discrimination Capabilities of a Multitransducer Single-Chip Gas Sensor System

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