Sub-ppb mercury detection in real environmental samples with an improved rhodamine-based detection system

Abstract

A new procedure is described for the determination of Hg 2+ ions in water samples. A Rhodamine based fluorescent sensor was synthesized and the experimental conditions were specifically optimized for application to environmental samples, which requires low detection limits and high selectivity in competitive experiments with realistic concentrations of other metal ions. Incorporation of a Rhodamine-6G fluorophore to a previously described sensor and optimization of the buffer system (detection with acetic acid at pH 5.25) enabled significant enhancement of the sensitivity (detection limit = 0.27 µg.L -1 ) and selectivity. The optimized procedure using high-throughput microplates has been applied to tap and river waters with good results.

Characterization of a Hg2+-Selective Fluorescent Probe Based on Rhodamine B and Its Imaging in Living Cells

“…By contrast, other metal ions and anions had almost no influence on the fluorescent spectra of P ( Figure 2 ). Most likely, it was the addition of Hg 2+ to P that caused the opening of the spirolactam in the structure of the rhodamine part [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ], inducing an enhancement in fluorescence intensity. Furthermore, for the further study of the selectivity of P , a competition experiment was also conducted ( Figure S2 ); all the tested metal ions and anions did not show any obvious interference to the response of P with Hg 2+ , except I − had some influence on the response of P .…”

“…As to visualizing the subcellular distribution of metal ions in physiological processes, fluorescence imaging techniques have become a powerful tool [ 18 ]. Some Hg 2+ -selective fluorescent probes derived from rhodamine have been reported [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. However, these reported rhodamine-based Hg 2+ -selective fluorescent probes still have shortcomings that need to be overcome, such as cross-sensitivities toward other metal ions and anions [ 27 ], pH dependency [ 28 ], and non-suitability for cell imaging [ 22 , 23 ], which could lower the sensitivity and limit the practical application of probes in environmentally and biologically relative targets.…”

“…Some Hg 2+ -selective fluorescent probes derived from rhodamine have been reported [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. However, these reported rhodamine-based Hg 2+ -selective fluorescent probes still have shortcomings that need to be overcome, such as cross-sensitivities toward other metal ions and anions [ 27 ], pH dependency [ 28 ], and non-suitability for cell imaging [ 22 , 23 ], which could lower the sensitivity and limit the practical application of probes in environmentally and biologically relative targets. Compared with some successful fluorescence “turn-on” probes for imaging intracellular metal ions, such as Cu 2+ [ 29 ], Al 3+ [ 30 ], and Mg 2+ [ 31 ], the development of highly selective, sensitive, and cell membrane-penetrable Hg 2+ fluorescent probes with “off–on” signals is still a bottleneck.…”

Integrated microfluidic platforms for heavy metal sensing: a comprehensive review

“…Rhodamine and its derivatives are being used in detecting heavy metals like Cd 2+ and Pb 2+ , Cd 2+ and Hg 2+ . 63–65…”

Fabrication of a Label‐free Femtomolar Electrochemical Mercury Ion Biosensor Based on Oligonucleotide Receptor Layers Hybridized with Multi‐walled Carbon Nanotubes

“…Several traditional techniques like chromatography [5], atomic fluorescence spectrometry (AFS) [6], atomic absorption spectroscopy (AAS) [7], X-ray absorption spectroscopy (XAS) [8], cold vapour atomic fluorescence spectrometry (CV-AFS) [9,10], inductively coupled plasma atomic emission spectrometry (ICP-AES) [11,12], and inductively coupled plasma mass spectrometry (ICP-MS) [13,14], are developed to address the issue, but these techniques are less efficient, inconvenient, expensive, time consuming, and require skilled professionals. Meanwhile, various optical techniques including colorimetric [15][16][17][18], fluorescent [19][20][21] and several electrochemical techniques have also been demonstrated [22][23][24][25][26][27][28]. However, these techniques proved inconvenient for on-spot detection of mercury in an aqueous medium and also costlier.…”