Fibre optics photometric

Flow-through optical sensors bearing one or more immobilized enzymes at their sensing microzone can be classified according to the type of physical relationship between the microzone and the detection system or instrument used into those using fibre optics (photometric and luminemetric) and those integrating a biochemical reaction and detection (usually photometric). 

Initially fibre optic chemical sensors were simply devices for modifying the light path of a conventional spectrometer. The optical fibres were just used to conduct light to and from the sample. Sometimes conventional colorimetric reactions were carried out on the sample, and specialized probes could be used in conjunction with the optical fibres to make absorption measurements (for example). Such devices can be described as photometric or spectroscopic transducers. 

Radiometers consists of filters, a sensor (silicon radiation detectors, which are sensitive in the range 200-1100 nm, or vacuum photodiodes with specific photocathode materials) and an input optical attachment such a cosine correction diffuser or fibre optic assembly [1762, 1770]. The current of the sensor is converted to a voltage by the converter module . This output voltage (0-5 V) can monitor the relative intensity of emitted radiation of 0-100%. This value can simply be displayed using an analogue or digital instrument, calibrated in any radiometric and/or photometric units. 

The exploitation of a mini-chamber is the essence of the flow-batch system (5.5.3), and hence the implementation of LLE in this system is best accomplished with this device. This was demonstrated in the spectro-photometric determination of cocaine relying on the formation of a cocaine—cobalt thiocyanate complex and extraction into chloroform [191]. The solutions involved were inserted into a reaction chamber and an optical fibre allowed absorbance measurements without the need for phase separation. Good analytical figures of merit were reported. 

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