Review of Chemical Sensors for In-Situ Monitoring of Volatile Contaminants

Abstract

This report presents a review of sensors and technologies that are capable of detecting and monitoring volatile organic compounds. The scope of this review was limited to those sensors that have the potential to be used in geologic environments for long-term monitoring applications. Four general categories of sensor technologies were reviewed: (1) chromatography and spectrometry; (2) electrochemical sensors; (3) mass sensors; and (4) optical sensors. Based on the review criteria set forth in this report, the most viable sensors for in-situ chemical sensing appear to be electrochemical sensors (specifically conductometric sensors), fiber-optic sensors, and surface-acoustic-wave sensors. However, very few chemical sensors have been successfully demonstrated in realtime, continuous, in-situ applications.iv Acknowledgments

Untitled

“…A metaloxide sensor is a thick film detector made by coating a film of tin oxide sintered on a small ceramic tube [21,22]. When the sensor is exposed to an atmosphere containing gases, the tin-dioxide surface adsorbs these gas molecules and cause oxidation allowing a change in conductivity.…”

“…Un senzor pe bazã de oxid de metal este un detector cu peliculã groasã realizat prin acoperirea unui mic tub ceramic cu o peliculã de oxid de staniu sinterizat [21,22]. Când senzorul este expus la o atmosferã care conþine gaze, suprafaþa staniu-dioxid adsoarbe aceste molecule de gaz ºi determinã oxidarea, permiþând o modificare a conductivitãþii.…”

In-Situ Chemiresistor Sensor Package for Real-Time Detection of Volatile Organic Compounds in Soil and Groundwater

“…Ho et al [2] performed a review of chemical sensors that are potentially applicable to long-term insitu monitoring applications. Polymer-absorption conductometric sensors were found to be one of the most viable candidates for in-situ applications because of their simplicity, and they have been considered by the U.S. Environmental Protection Agency for use in detecting VOC spills from underground storage tanks [3][4].…”

“…An attractive alternative is the use of real-time sensors that can be placed in situ, which would reduce the need for manual samples and expensive offsite analyses. However, while technology exists to detect and analyze VOCs, very few systems are designed to be deployed in situ (e.g., in soil and water) while providing real-time, continuous, longterm monitoring [2]. Many of these devices include sensitive electronic components and require the flow of a carrier gas during operation, which may not be amenable to long-term in-situ monitoring applications.…”

Preparação e caracterização de sensores de amônia baseados em filmes ultrafinos de polianilina e polianilina-ftalocianinas.

“…Ho e colaboradores [8] realizaram estudos chegando a conclusão de que para aplicações in-situ em geral, como no caso de criação de frangos, os sensores mais apropriados são os eletroquímicos, especificamente os sensores baseados em variação de condutividade, devido à sua robustez e simplicidade. Dentre os tipos de sensores de gases eletroquímicos que trabalham com variação de condutividade, estão os sensores baseados em semicondutores e os baseados em filmes poliméricos, como a polianilina (PAni).…”