Fluorescent optical chemical sensors concentration

From a general point of view, a chemical sensor is a device capable of continuously monitoring the concentration of an analyte. The two main classes are electrochemical sensors and optical chemical sensors. The latter are based on the measurement of changes in an optical quantity refractive index, light scattering, reflectance, absorbance, fluorescence, chemiluminescence, etc. For remote sensing, an optical fiber is used, and the optical sensor is then called an optode because of... 

Major Applications pH Sensors, optical chemical sensors, biochemical sensors, biosensors," fluorescent pH detector system, measuring fluorescence lifetime in cells, determining concentration of a laminar sample stream, fluorescent reporter beads for fluid analysis, measuring ch ical analytes, intracellular pH in human sperms, " multidrug resistance," recording intramitochon-drial pH, fluorescent probes ... 

C. Ion sensing. Several different schemes can be applied to fiber-optic chemical sensors for detecting ions other than hydrogen. One approach is to design a system, similar to pH fiber-optic chemical sensors, in which a dye that selectively binds a metal ion of interest is immobilized in an ion-permeable polymer such as cellulose or a hydrogel at the tip of an optical fiber. The reaction between the dye and the ion changes the absorbance or fluorescence of such dyes. Absorbance or fluorescence intensity changes are measured as a function of ion concentration, but this... 

Lubbers D.W., Opitz N., Optical fluorescence sensors for continuous measurement of chemical concentrations in biological systems, Sensors Actuat. 1983 3 641. 

Optical sensors for oxygen measurement are attractive since they can be fast, do not consume oxygen and are not easily poisoned. The most common method adopted in construction is based on quenching of fluorescence from appropriate chemical species. The variation in fluorescence signal (I), or fluorescence decay time (x) with oxygen concentration [O2] is described by Stem-Volmer equation91 ... 

The intrinsic sensors are based on the direct recognition of the chemicals by its intrinsic optical activity, such as absorption or fluorescence in the UV/Vis/IR region. In these cases, no extra chemical is needed to generate the analytical signal. The detection can be a traditional spectrometer or coupled with fiber optics in those regions. Sensors have been developed for the detection of CO, C02 NOx, S02, H2S, NH3, non-saturated hydrocarbons, as well as solvent vapors in air using IR or NIR absorptions, or for the detection of indicator concentrations in the UV/ Vis region and fluorophores such as quinine, fluorescein, etc. 

In comparison to equivalent optical detection methods using whole cell biosensors for water toxicity detection, these results proved to be more sensitive and produce faster response time. Concentrations as low as 1% of ethanol and 1.6 ppm of phenol could be detected in less than 10 min of exposure to the toxic chemical, whilst a recent study [11] which utilized bioluminescent E.coli sensor cells, detected 0.4 M (2.35%) ethanol after 220 min. An additional study [1] based on fluorescent reporter system (GFP), enabled detection of 6% ethanol and 295 ppm phenol after more than one hour. Cha et al [12] used optical detection methods of fluorescent GFP proteins, detected 1 g of phenol per liter (1,000 ppm) and 2% ethanol after 6 hours. Other studies [13] could not be directly compared due to different material used however their time scale for chemicals identification is hours. 

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