Chromotropic acid, a fluorogenic chelating agent for aluminium(III)

Abstract

Complexation of aluminium(III) with the fluorogenic ligand chromotropic acid (4,5-dihydroxynaphthalene-2,7-disulfonic acid) has been revisited with the aim of using enhancement of the fluorescence intensity as an analytical tool. Complexation at the optimum pH approximately 4 was shown to lead to a 1:1 complex with a stability constant log beta110=18.4 +/- 0.7. The fluorogenic effect was thoroughly investigated. Nearly selective excitation of the chelate rather than the ligand could be achieved at wavelengths longer than 360 nm. For analytical purposes the main interfering ion was Ga3+. The strongest competing ligand was shown to be citric acid. Competitive complexation by acetate or formate ions can also make their use in a buffer at the usual concentration, 0.2 mol L(-1), questionable, whereas a 10(-2) mol L(-1) formic acid buffer was shown to be a good alternative. The calibration plot showed that the dependence of response on Al(III) concentration was linear up to 500 microg L(-1); the detection limit was 0.65 microg L(-1) (3 SDblank, n=10, SD= +/- 1.4% at 10 microg L(-1) and +/- 0.8% at 100 microg L(-1)). The analytical procedure was successfully applied to several samples of tap water and the results were in good agreement with those from AAS determination.

A review of new methods of surface chemical modification, dispersion and electrophoretic deposition of metal oxide particles

“…It is known that CHR forms complexes with different metal ions and shows good adsorption on different surfaces. 99,[115][116][117][118] The adsorption mechanisms can be attributed to bidentate chelating bonding or bidentate bridging bonding, including inner sphere and outer sphere bonding (Fig. 5B), which involves two OH groups of CHR.…”

Water-soluble optical sensors: keys to detect aluminium in biological environment

“…However, discrepancies related to the absence of wide-range studies on the increase in emission intensity with Al 3+ ion, binding stoichiometry, and use of acetic acid/acetate buffer (pH = 4.0) made Bardez and coworkers revisit the sensing properties of 1 in 2004. 45 An increase in absorption at 360 nm ( Fig. 3a ) and a fluorescence enhancement at 387 nm ( Fig.…”

Valence Discriminative Detection of Metal Cations by a Chromotropic Acid-grafted Glassy Carbon Electrode

“…4 and 5(b), the CA moiety did not respond to trivalent cations both electrochemically and spectrophotometrically at pH 1.0. According to the literature, 22 optimum pH range for Al(III) determination with CA was reported to be from 3 to 4 in the spectrophotometric or spectrofluorometric measurement. Therefore, the pH value of the sample solution was varied from 1 to 4 to improve the response of the trivalent cations.…”