Effects of room temperature ionic liquids on fluorescence characteristics of 17β-estradiol and its derivative.

Previous reports have seldom concerned about the RTILs (Room temperature ionic liquids), and their effects on derivatization reaction or derivatives. In this study, we reported that the effects of four different RTILs, i.e., [EMIM]PF(6), [BMIM]PF(6), [HMIM]PF(6) and [OMIM]PF(6), on fluorescence spectra of 17 β-estradiol (E2), and its derivatization solvent dansyl chloride (DNSCl) and the derivative. [BMIM]PF(6) had a significant quenching effect on the fluorescence intensity of E2, suggesting the formation of [BMIM]PF(6)/E2 complexes and possible buried E2 molecular in a more hydrophobic microenvironment. The estimated Stern-Volmer quenching constant (Ksv=0.3519) proved that E2 quenching caused by [BMIM]PF(6) was a dynamic quenching process. Four RTILs, with different alkyl chain-length in imidazolium cation, resulted in different quenching intensities to E2 as follows: [EMIM]PF(6) > [BMIM]PF(6) > [HMIM]PF(6) > [OMIM]PF(6). At 5 mg L(-1) of DNSCl, [BMIM]PF(6), [HMIM]PF(6) and [OMIM]PF(6) increased the fluorescence intensities of E2 in water by 8.5, 7.6 and 6.1 times, respectively, and a 37-nm hypsochromic shift occurred. The fluorescence intensity for [BMIM]PF(6)-extracted derivative of E2 increased more than two times compared with that for the control. In conclusion, this study demonstrated that above four hexafluorophosphate salt ionic liquids could be used in derivatization reaction to enhance fluorescent sensitivity in E2 trace residual analysis. © Springer Science+Business Media, LLC 2011