Effects of imidazolium room temperature ionic liquids on the fluorescent properties of norfloxacin.

The effects of 12 imidazolium room temperature ionic liquids (RTILs), including [C(n)mim]BF4, [C(n)mim]PF6, and [C(n)mim]Br (n = 4, 6, 8, 10), on the fluorescent properties of norfloxacin were examined. The fluorescence intensity of norfloxacin at 0.1 mg/L in methanol significantly increased with the addition of [C(n)mim]BF4 and [C(n)mim]PF6 into the solvent at 0.1-15.0%. The sensitizing effect may result from the higher viscosity of the RTILs-methanol mixture solvent than that of the methanol itself. However, the quenching effect on fluorescence of norfloxacin was observed in [C(n)mim]Br-methanol solvent. The fluorescence intensities of norfloxacin decreased with an increase in the alkyl chain length of the alkyl substituents of the imidazolium ring of RTILs. The main interaction between the RTILs and norfloxacin is not by hydrogen bonding. The fact, that some RTILs can significantly sensitize fluorescence of norfloxacin, indicates that RTILs could be a group of promising solvents for development of sensitive spectrofluorimetric methods for determination of norfloxacin at ultra-trace levels in environmental samples.