Abstract
The development of chemical sensors for monitoring the levels of organic pollutants in the aquatic environment has received a great deal of attention in recent decades. In particular, the mid-infrared (MIR) sensor based on attenuated total reflectance (ATR) is a promising analytical tool that has been used to detect a variety of hydrocarbon compounds (i.e., aromatics, alkyl halides, phenols, etc.) dissolved in water. It has been shown that under certain conditions the MIR-ATR sensor is capable of achieving detection limits in the 10–100 ppb concentration range. Since the infrared spectral features of every single organic molecule are unique, the sensor is highly selective, making it possible to distinguish between many different analytes simultaneously. This review paper discusses some of the parameters (i.e., membrane type, film thickness, conditioning) that dictate MIR-ATR sensor response. The performance of various chemoselective membranes which are used in the fabrication of the sensor will be evaluated. Some of the challenges associated with long-term environmental monitoring are also discussed.
Highlights
Water is an essential commodity for all aspects of life and preserving the world’s natural water resources is one of the key issues of the 21st century
One particular analytical tool that does not appear to be severely affected by chemical interferences and turbidity is the mid-infrared (MIR) sensor based on attenuated total reflectance (ATR)
A number of sensors have been developed over the past several decades to directly measure BTEX levels in water, many of them are unsuitable for environmental monitoring since they struggle to clearly resolve and separate the signals arising from the various aromatic components
Summary
Water is an essential commodity for all aspects of life and preserving the world’s natural water resources is one of the key issues of the 21st century. One particular analytical tool that does not appear to be severely affected by chemical interferences and turbidity is the mid-infrared (MIR) sensor based on attenuated total reflectance (ATR). In recent years there has been a shift towards the use of IR for the detection of a number of environmentally relevant pollutants in water and this has paved the way for a wide range of applications in biomedical [9] and process monitoring [10]. Since a number of articles have been published in this area, it seems timely to review the development of IR-based sensors in addressing the issues and challenges facing environmental monitoring of hydrocarbon contaminants. This article will focus mainly on the MIRATR sensor that employs a trapezoidal IRE, noting that various reviews have been recently published discussing the development and application of optical fibers for mid-IR sensing [18,19]
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