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Proceedings Paper

Fluorescent ion indicators for detecting heavy metals
Author(s): Michael A. Kuhn; Brian Hoyland; Scott Carter; Cailan Zhang; Richard P. Haugland
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Paper Abstract

A series of fluorescent ion indicators were tested for their spectral response to submicromolar levels of 13 divalent and trivalent metal ions in aqueous solution. Upon binding their target ions, these fluorescent compounds exhibit changes in fluorescence emission intensity that are easily detectable, making them useful for direct the detection of soluble heavy metal ions including Hg2+, Cu2+, Ni2+ and Cd2+. The fluorescence response of these indicators to ion binding results from photoinduced electron transfer effects, fluorophore/quencher interactions, fluorescence quenching by heavy metal ions or a combination of these processes. The majority of the indicators we tested bind their target ions reversibly with dissociation constants (Kd) near 1 (mu) M (approximately 1 ppm) and detection limits near 100 nM (approximately 100 ppb) at pH 7. However, several indicators exhibit very high affinity for their target ion; for example, Magnesium GreenTM binds Zn2+ with a Kd near 20 nM. All the indicators synthesized and tested are based on water-soluble fluorophores that have high fluorescence quantum yields (from 0.3 to 0.7) and can be excited with an Ar laser, fluorometer or hand- held UV lamp. Furthermore, the excitation and emission spectra of these indicators are insensitive to pH changes over the range of 5 to 10, as well as to high concentrations of K+, Na+, Ca2+ and Mg2+. These properties make the indicators useful for the direct measurement of metal ions in solutions, such as biological fluids, sea water and waste streams, that contain high concentrations of salts.

Paper Details

Date Published: 8 May 1995
PDF: 7 pages
Proc. SPIE 2388, Advances in Fluorescence Sensing Technology II, (8 May 1995); doi: 10.1117/12.208483
Show Author Affiliations
Michael A. Kuhn, Molecular Probes, Inc. (United States)
Brian Hoyland, Molecular Probes, Inc. (United States)
Scott Carter, Molecular Probes, Inc. (United States)
Cailan Zhang, Molecular Probes, Inc. (United States)
Richard P. Haugland, Molecular Probes, Inc. (United States)

Published in SPIE Proceedings Vol. 2388:
Advances in Fluorescence Sensing Technology II
Joseph R. Lakowicz, Editor(s)

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