pH-Independent Fluorescent Chemosensor for Highly Selective Lithium Ion Sensing

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+, b...

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Bibliographic Details
Published in:Analytical chemistry (Washington) 2007-02, Vol.79 (3), p.1237-1242
Main Authors: Citterio, Daniel, Takeda, Junichiro, Kosugi, Masaki, Hisamoto, Hideaki, Sasaki, Shin-ichi, Komatsu, Hirokazu, Suzuki, Koji
Format: Article
Language:English
Subjects:
Analytical chemistry
Binding Sites
Cations - analysis
Chemistry
Electrochemical methods
Exact sciences and technology
Fluorescence
Fluorescent Dyes
General, instrumentation
Humans
Hydrogen-Ion Concentration
Lithium
Lithium - analysis
Lithium - blood
Sensors
Spectrometric and optical methods
Spectrometry, Fluorescence
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Summary: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+, Ca2+, Mg2+), a selectivity of log k Li+,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+.
ISSN:0003-2700
1520-6882
DOI:10.1021/ac061674g