Fluorescent water-tracing compounds

Water-Tracing Compounds. Another application of these fluorescent pyridones has been the development of a series of coaipounds useful as ground-water tracers. Smart and Laidlaw have outlined several qualities desirable in fluorescent water-tracing compounds (.18). 

The increased use of IV-methyl carbamate insecticides in agriculture demands the development of selective and sensitive analytical procedures to determine trace level residues of these compounds in crops and other food products. HPLC is the technique most widely used to circumvent heat sensitivity of these pesticides. However, HPLC with UV detection lacks the selectivity and sensitivity needed for their analysis. In the late 1970s and early 1980s, HPLC using post-column hydrolysis and derivatization was developed and refined with fluorescence detection to overcome these problems. The technique relies on the post-column hydrolysis of the carbamate moiety to methylamine with subsequent derivatization to a fluorescent isoindole product. This technique is currently the most widely used HPLC method for the determination of carbamates in water" and in fruits and vegetables." " ... 

V. Sivaprakasam and D. K. Killinger, Tunable ultraviolet laser-induced fluorescence detection of trace plastics and dissolved organic compounds in water, Appl. Opt. 42,6739-6746 (2003). 

Another extremely useful method for cac determination, especially in the light of high sensitivity, is fluorescence emission spectroscopy [15]. Some aromatic water-insoluble dyes that are present in trace amounts in mixed polyelectrolyte-surfactant solutions have an ability to solubilize within the self-assembled surfactant aggregates and to change their photophysical properties because of the change of environmental polarity. Through this, they offer a very sensitive method for the determination of cac values. A typical and lately frequently used compound is pyrene, which is used as a fluorescence probe to assess various micellar properties. Pyrene exhibits a polarity dependent fluorescence spectrum with the ratio /,//3 (the ratio of the intensity... 

LLCs are promising candidates as probes for humidity sensors due to the distinct quenching effect of water molecules which can reversibly coordinate to lanthanide ions. The decrease in lifetime of the Dq transititMi of europiumflll) perchlorate was used for the determination of small amounts of water in DMF and DMSO [106]. Wang and Li have presented luminescent nanospheres for die determination of small amounts of water (0.05-3.0 vol%) in ethanol [107]. They coated silica nanoparticles with a thin layer of a salicylic acid-La /Tb " coordination compound. The green fluorescence peaking at 549 nm corresponds to the D4 transition of Tb and is strongly quenched by trace amounts of water. The nanoparticles can be excited at wavelengths around 350 nm. 

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