Use of light as a reaction ingredient

In contrast with the sensors described elsewhere in this Chapter, the device proposed by the authors group uses no reagent, but photons, to induce a photochemical reaction, and involves electrochemical detection of the photochemical product, which allows one to continuously monitor the formation of the electroactive product. Kinetic monitoring increases the selectivity of determinations by eliminating matrix effects and the contribution of side reactions, whether slower or faster than the main reaction. The electrochemical system chosen for implementation of this special sensor was the Fe(II)/C204 couple, which was used for the kinetic determination of oxalate ion based on the following reaction  

Sensors based on integrated reaction and detection are the most varied and numerous among flow-through sensors and those that will predictably experience the greatest development in the near future. Both enzyme sensors and immunosensors are bound to become virtually irreplaceable tools in some areas of social interest including clinical and environmental analysis. While other sensors inspired by those discussed in Sections 3.4 and 3.5 may 

Flow-through sensors based on integrated separation and detection 

One of the most topical ways of approaching this type of system, where separation and detection take place sequentially in space and time, to current trends in Science and Technology (e.g. automation and miniaturization) involves integrating both steps. Integrated systems of this type meet the requirements of chemical sensors [7,8] and differ clearly from conventional flow systems, where detection and mass transfer take place at different locations in the continuous configuration. In fact, the characteristic mass transfer of separation techniques takes place simultaneously with detection 

The above exceptions leave relatively few sensors based on integrated separation and detection, particularly of the types involving gas-liquid and liquid-liquid interfaces, which require the detector to be responsive to the gas or ion (molecule) transferred across the membrane. The scope of liquid-solid interactions is somewhat broader as it enables not only retention of the analyte and monitoring of some intrinsic property, but also to retain a product of a previous reaction, thereby substantially expanding the possibilities. 

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