Search

The article presents the results of the ascorbic acid (AA) determination with using a complex of an Tb (III) ion with ciprofloxacin (CF) as a lanthanide luminescent marker. The luminescent properties of the Tb (III)-CF complex in the presence of AA were studied. The excitation and luminescence spectra, triplet level of ligand, the kinetics of the luminescence decay of the Tb(III)-CF complex in the presence of AA were analyzed. The excitation spectrum of the Tb (III)- CF complex has broad bands with maxima at 302 and 355 nm that corresponding to the n^n* electronic transition in the absorption spectrum of ligand. The luminesce spectra demonstrate the emission transitions arising from 5D4 energy level to 7Fj multiplet ground state. The luminescence of the Tb(III)-CF complex was found to be quenched by AA. It was established that the lifetime of the excited 5D4 state of the Tb (III) ion decreases with AA concentration increasing up to 0,25 mg/cm3. Luminescence quenching of the Tb (III)-CF complex by AA follows the Stern-Volmer relationship of AA. The Stern-Volmer constant K is 2478 dm3/mol. The biomolecular quenching rate constant kq is 1,25-107 dm3/mol. The effect of luminescence quenching of the Tb (III)-CF complex was used to developing the procedure for determining of AA in the dietetic additives «Asvitol» and «Ascorbic acid». The linear calibration plot for AA was obtained over the concentration range of 0,02 to 0,25 mg/cm3. [ABSTRACT FROM AUTHOR]

Tb(IH)-2,2'dipyridyl complex is offered to be used as a luminescent sensor for methylparaben determination. The luminescent properties of the complex of Tb(IH) ion with 2,2'-dipyridil and methylparaben in a solid layer of sorbent were studied: absorption spectra, luminescence, excitation, the triplet levels of the ligands. It is established that the complex is efficient transfer of excitation energy from the ligand to the lanthanide ion, resulting in intense luminescence of the latter. The optimal conditions of complex formation were selected: the optimal concentration of solutions of terbium chloride (III), dipyridyl, methylparaben. The method of direct fluorescent determination of methylparaben in the means for removing makeup on the sensitized luminescence of ion Tb(III) was developed. The detection limit of methylparaben in means for removing makeup is 2,7 10-3 mg/sm3. This method advantageously differs from existing by absence of toxic reagents, expensive equipment, by short duration of analysis, allows to carry out rapid skrining of different cosmetic products. [ABSTRACT FROM AUTHOR]

As a luminescent sensor for citrate-ions definition it is suggested to use a complex yttrium (III) - routin - citrate-ion with a ratio of components 1:1:1. Optimum conditions of mixed-ligand complex formation are determined, his spectral and luminescent characteristics (wavelength maximum of luminescence and excitement) are defined. Optimum conditions of a complex formation are chosen: optimum concentration of solutions - yttrium chloride (III), routin, trisodium citrate. The method of luminescent determination of citrate - ions in sweet soft drinks, based on the use of a rutin's molecular luminescence in the mixed-ligand complex Y(III) - Rut - Cit is developed. The detection limit of citrate-ion in sweet soft drinks is 2,7 10-3 mg/ml. A method advantageously differs from existing by absence of toxic reagents, expensive equipment, by short duration of analysis, allows to carry out rapid skrining of different sweet soft drinks. [ABSTRACT FROM AUTHOR]