Species-differentiable sensing of phosphate-containing anions in neutral aqueous solution based on coordinatively unsaturated lanthanide complex probes

A new chromogenic/fluorogenic molecular probe was developed for highly selective and species-differentiable detection of phosphate-containing anions in neutral aqueous solution. The coordinatively unsaturated lanthanide complex, made from Eu(III) ion and 2-[(8-hydroxy-5-sulfo-7-quinoline)azo]-1,8-dihydroxy-3,6-naphthalene disulfonic acid, changed its conformation when binding to the incoming target anions, which resulted in differential absorption or fluorescence responses. It was demonstrated that not only phosphate and pyrophosphate but also DNA and RNA could be clearly distinguished by visible absorption or fluorescence spectra. Also, differential responses in absorption spectra were observed when AMP, ADP, and ATP were added into the sensing system. Selective quantitation of these phosphate-containing anions in aqueous solutions, therefore, can be easily available. DNA and RNA were distinguished by different colors and independent fluorescence emissions due to their intrinsic differences in β- d-ribose residues. Simultaneous or independent quantitation of DNA and RNA in a mixture sample, therefore, is possible without pretreatment with nuclease. Furthermore, the influence from the base selectivity can be eliminated by the use of the probe. The detection limits of phosphate and 5 ′-ATP in neutral water were 6.0 × 10 −7 and 9.0 × 10 −7 M, respectively, by the UV/Vis spectrophotometric method; the detection limits were 12.3 ng/mL for DNA by fluorimetry and 2.3 mg/L for RNA by UV/Vis spectrophotometry.