Enhancement phenomenon

Kleinerman and co-workers (158) reported an enhancement of fluorescent yield of chelated lanthanide ions by Lewis bases. They observed that in liquid, plastic, and glassy solutions containing terbium europium, and samarium chelates, the use of Lewis bases accomplishes the same effect as substituting deuterium for hydrogen. Not all bases, however, are equally effective. The molecular size of the base does not appear to be particularly important, since strong enhancement effects can be obtained with both bulky and small molecules. The nature of the atom of the base having the unshared electron pair is not a determining factor in the enhancement phenomenon. 

Interactions of ofloxacin and levofloxacin with Al3+, Fe3+, and Mg2+ ions were investigated by capillary zone electrophoresis (07CHR489). A fluorescence enhancement phenomenon in the europium-ofloxacin-sodium dodecyl benzenesulfonate fluorescence system was observed when Gd3+ was added (07JFL105). A quantitative relation was found between the relative fluorescences of Zr, Mo, and V chelates of ofloxacin and the ionization of the carboxylic group and the calculated stability constants of the formed chelates (06MI34). Factors that significantly influence the stability of ofloxacin- and levofloxacin-metal (Al3+, Fe3+, Cu2+,... 

All recent studies indicate that cavitation plays an important role in the enhancing mechanism. Several attempts have been made to establish a suitable mathematical model that will describe the enhancement phenomenon and predict the enhancement ratio for different drugs in various conditions [64,65],... 

Nakajima A. A study of the system of pyrene and p-cyclodextrin in aqueous solution utilizing the intensity enhancement phenomenon, Spectrochim Acta A 1983 39 913-5. 

Spectral characteristics and selection of surfactant. Increase in the fluorescence intensity of the carbaryl solution was observed using SDS as surfactant at excitation and emission wavelengths of 281 nm and 349 nm respectively (Fig. 1). As can be seen from Fig. 1, Triton X-100 and dodecyl pyridinium chloride (DPC) decreased the fluorescence. This phenomenon clearly indicates that cationic surfactant (DPC) and neutral surfactant (Triton X-100) have negative effects on the fluorescence intensity for carbaryl while anionic surfactant (SDS) enhances the fluorescence intensity of carbaryl. This surfactant-enhanced phenomenon by SDS was used for the spectrofluorimetric determination of carbaryl. 

We noted that the enhancement phenomenon is diminished at higher gas phase concentrations. There may be a limit to the number of extra molecules that the condensing water is dragging along. 

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