pH-independent fluorescent chemosensor for highly selective lithium ion sensing

Daniel Citterio, Junichiro Takeda, Masaki Kosugi, Hideaki Hisamoto, Shin Ichi Sasaki, Hirokazu Komatsu, Koji Suzuki

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Abstract

Since lithium salts are used as pharmaceutically active compounds against manic-depressive psychosis, there is a demand to monitor the lithium concentration in blood in the narrow range of 0.6-1.2 mM effectively and safely. Here we report on an optical sensor approach for the determination of Li +, based on the design and synthesis of a novel lithium fluoroionophore KLI-1 and its polymer immobilizable derivative KLI-2, and the application to an optode. The novel lithium fluoroionophores rely on a tetramethyl "blocking subunit" bearing 14-crown-4 as a Li +-selective binding site and 4-methylcoumarin as a fluorophore, intramolecularly connected to show ICT-type wavelength shift for ratiometric fluorescence measurements. The fluoroionophores showed high selectivity for Li+ with binding-induced blue shift in the fluorescence spectra, no response to major biological interfering cations (K+, Ca 2+, Mg2+), a selectivity of log kLi+,Na+ = -2.4 over Na+ in solution, and no response to pH in the range of pH 3-10. A hydrophilic optode membrane with KLI-2 immobilized also showed good selectivity for Li+, pH independence in the physiological range (pH 6-8), and fully reversible signal changes. KLI-1 and KLI-2 are excellent Li + fluorescent chemosensors that can be applied to quantitative measurements of lithium in clinical samples, although possible interference from Na+ has to be considered at the lower therapeutic level of Li +.

Original languageEnglish
Pages (from-to)1237-1242
Number of pages6
JournalAnalytical chemistry
Volume79
Issue number3
DOIs
Publication statusPublished - 2007 Feb 1
Externally publishedYes

ASJC Scopus subject areas

  • Analytical Chemistry

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  • Cite this

    Citterio, D., Takeda, J., Kosugi, M., Hisamoto, H., Sasaki, S. I., Komatsu, H., & Suzuki, K. (2007). pH-independent fluorescent chemosensor for highly selective lithium ion sensing. Analytical chemistry, 79(3), 1237-1242. https://doi.org/10.1021/ac061674g