Selective fluorometric “Turn-off” sensing for Hg2+ with pyrazoline compound and its application in real water sample analysis

Abstract

In this study, a new pyrazoline derivative (4-(3-phenyl-3a,4-dihydroindeno[1,2-c]pyrazol-2(3H)-yl)benzenesulfonamide, K1) was described as fluorescent probe for fluorometric detection of Hg2+. This fluorescence probe had a high selectivity only toward Hg2+ ion in the 19 metal ions (Li+, Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Cd2+, Zn2+, Cu2+, Hg2+, Cr2+, Pb2+, Fe2+, Mn2+, Co2+, Fe3+, Al3+ and Cr3+). It was observed that Hg2+ ions significantly decrease the fluorescence intensity of K1, but the fluorescence intensity of K1 did not changed in the presence of the other metal ions. Limit of detection (LOD) value was calculated as 0.16 µM for Hg2+ while the binding constant was calculated as 4.69 × 105 M−2 via fluorescence measurements. The values obtained by this study were very good compared to our previous Hg2+ sensor study which was realized with a different pyrazoline compound. The interaction between of K1 and Hg2+ was not interfered by the presence of other metal ions. In addition, the type of interaction was reversible. It was found that the relative standard deviations (RSD) of three measurements were less than 15% with the real sample tests performed in the tap water and its response time was less than 0.5 min. In conclusion, the new pyrazoline derivative K1 is a highly selective and sensitive fluorescence probe for the detection of Hg2+ ion and it has a great chance for practical application.