Sensors environmental considerations

Over the last decade, interest in release and delivery of VOCs has been steadily growing, with a particular focus on food, environmental and medical applications [186-190]. Consequently, considerable effort was invested to develop analytical methods capable of capturing such dynamic VOC release processes (Fig. 15.14) [179, 191]. This led to improvements in electronic sensor methods (often termed electronic noses ) [192]. 

A related problem associated with efforts to characterize redox conditions of environmental materials is the lack of equilibrium among the chemical constituents of an environmental system (138-141) or between the environmental constituents and a sensor material (142). Thus, even techniques that are based on specific redox active species—such as H2 (143-146), Hg (147), indicator dyes (148, 149), or other mediators (137)— cannot provide a general characterization of redox conditions. However, we do recommend techniques that quantify the activity of specific oxidants or reductants, because they are necessary for the rigorous application of the approach Section 5.1 describes. Similar considerations apply to the characterization of redox kinetics. 

The future of anion sensors is a very promising one. Greater interest and legal requirements for environmental, food and water monitoring will require the detection of anionic species, often at lower and lower concentrations. Technical problems, however, need to be overcome. These include some of the considerations below ... 

In the near future, the use of multifunctional polymer-based materials with separation/selective transport capabilities is also to be expected in the design of production systems with integrated environmental protection or inthe combination of chemical reactions and separation by attaching a catalytic functionality to the respective material [1]. Thus, those multifunctional materials should contribute materially to the development of clean energy and/or energy saving and therefore sustainable production technologies. In connection with these perspectives, there is considerable interest in new/modified polymer-based materials with tailored transport/catalytic properties. Also, many sensor applications are based on controlled permeation. 

Both empirical and rational methods have been successful in developing novel fluorescent sensors. However, on the one hand, empirical design and synthesis may require considerable trial and error. On the other hand, the rational design approach described above is limited to analytes that can sufficiently change the oxidation or reduction potential. Further, even in the case of theoretically designed molecules, the fluorescence properties may be unexpectedly influenced by environmental factors. The construction of libraries of fluorescent molecules is one way to overcome some of these problems in the development of novel fluorescent sensors. 

Much of the current agricultural abundance of the United States is due to the availabilty of chemical means of pest control. However, pesticides also represent a considerable threat to the environment when they are used improperly. For this reason the ability to measure pesticide residues at low concentrations in environmental matrices such as surface and groundwaters and soils is of great importance. In this paper we will describe a concept for a generic biosensor, the capacitive affinity sensor, capable of rapidly determining the concentration of many types of small molecules in the environment. 

Various analytical methods now employ amperometric measurements as part of their procedures. In particular, amperometric titrations have been widely used for the analysis of various substances in samples ranging from water to radioactive materials. Also, amperometric sensors, such as the dissolved oxygen probe and various amperometric biosensors, are widely used for clinical, environmental, and industrial monitoring. Furthermore, amperometric detectors have gained considerable use since the 1970s in high-performance liquid chromatographic determination of various substances and in flow injection analysis. 

---