Fluorimetry determination of trace Ce3+ with EDTP

Synthesis, structure, and fluorescence properties of coordination polymers of 3,5-bis(1′,2′,4′-triazol-1′-yl) pyridine

Four coordination polymers based on 3,5-bis(1′,2′,4′-triazol-1′-yl) pyridine were synthesized. Compounds [Cd₃(btc)₂(btap)(H₂O)₆] and [Cd(oa)(btap)] exhibited high sensitivity luminescence response towards Fe³⁺, Ce³⁺, Cr₂O₇²⁻ and MnO₄⁻ in aqueous solution.

A highly sensitive and selective spectrofluorimetric method for the determination of cerium at pico-trace levels in some real, environmental, biological, soil, food and bone samples using 2-(α-pyridyl)-thioquinaldinamide

A very simple, ultra-sensitive and highly selective non-extractive new spectrofluorimetric method is presented for the determination of cerium at pico-trace levels using 2-(α-pyridyl)-thioquinaldinamide (PTQA). PTQA has been proposed as a new analytical reagent for the direct non-extractive spectrofluorimetric determination of cerium(iv). This novel fluorimetric reagent, PTQA becomes oxidized in a slightly acidic (0.0005-0.0015 M H2SO4) solution with cerium(iv) in absolute ethanol to produce a highly fluorescent oxidized product (λ ex = 303 nm; λ em = 370 nm). Constant and maximum fluorescence intensities were observed over a wide range of acidity (0.0005-0.0015 M H2SO4) for the period between 5 min and 24 h. Linear calibration graphs were obtained for 0.001-600 μg L-1 of Ce, having a detection limit of 0.1 ng L-1; the quantification limit of the reaction system was found to be 1 ng L-1 and the RSD was 0-2%. A large excess of over 60 cations, anions and complexing agents (like, chloride, phosphate, azide, tartrate, oxalate, SCN- etc.) do not interfere in the determination. The developed method was successfully used in the determination of cerium in several certified reference materials (alloys, steels, noodles, ores and sediments) as well as in some environmental waters (potable and polluted), biological fluids (human blood, urine and milk), soil samples, food samples (vegetable, rice, corn and wheat), bone samples (human, cow, bull, fish, hen, goat, sheep), solutions containing both cerium(iii) and cerium(iv) and complex. The results of the proposed method for assessing biological, food and vegetables samples were comparable with ICP-OES and were found to be in excellent agreement.

Condensation Product of 4-Methoxybenzaldehyde and Ethylenediamine: "Off-On" Fluorescent Sensor for Cerium(III)

The condensation product (L) of 4-methoxybenzaldehyde and ethylenediamine has been synthesised and characterised. L showed a 21 times enhancement in fluorescence intensity on interaction with Ce³⁺ in CH₃OH at λ_max = 360 nm when excited with 270 nm photons. Metal ions K⁺, Na⁺, Al³⁺, Co²⁺, Hg²⁺, Cd²⁺, Ni²⁺, Zn²⁺, Mn²⁺, Mg²⁺ and Ca²⁺ do not interfere. The stoichiometry of binding and the binding constants were determined from spectroscopic data and found to be 1:1 and 10^4.8 M respectively. The detection limit was found to be 10^-5.2 M. The protonation/de-protonation of water molecules coordinated to Ce³⁺ was found to show interesting behaviour on the fluorescence of L:Ce³⁺.

A New Fluorescence Sensor for Cerium (III) Ion Using Glycine Dithiocarbamate Capped Manganese Doped ZnS Quantum Dots

A new fluorescence sensor for Ce(3+)ions is reported in this paper. This sensor is based on the fluorescence quenching of glycine dithiocarbamate (GDTC)-functionalized manganese doped ZnS quantum dots (QDs) in the presence of Ce(3+)ions. The synthesis of ultra-small GDTC-Mn:ZnS quantum dots (QDs) is based on the co-precipitation of nanoparticles in aqueous Solution. The nanoparticles are characterized with fluorescence spectroscopy, UV-vis absorption spectra, high-resolution transmission electron microscopy, X-ray power diffraction (XRD), and infrared spectroscopy. In the test carried out, it was found that the interaction between Ce(3+)ions and GDTC capped Mn:ZnS QDs quenches the original fluorescence of QDs according to the Stern-Volmer equation and the results show the existence of collisional quenching process. A linear relationship was observed between the extent of quenching and the concentration of Ce(3+)in the range of 2.0 × 10(-6) to 3.2 × 10(-5) mol.L(-1), with a detection limit of 2.29 × 10(-7) mol.L(-1). The relative standard deviation of 1.61% was obtained for five replicate measurements. The possible quenching mechanism was also examined by fluorescence and UV-vis absorption spectra. The interference of other cations was negligible on the quantitative determination of Ce(3+). This method proved to be simple, sensitive, low cost, and also reliable for practical applications.

Oxidation of an oligonucleotide-bound Ce(III)/multiphosphonate complex for site-selective DNA scission

Oligodeoxyribonucleotide conjugates of ethylenediamine-N,N,N',N'-tetrakis(methylenephosphonic acid) (EDTP) have been used to place a Ce(III)/EDTP complex in close proximity to predetermined phosphodiester linkages of a complementary target oligonucleotide. In the presence of atmospheric oxygen, the Ce(III) is oxidized into Ce(IV) which, in turn, efficiently cleaves the target phosphodiester linkage. No cleavage occurs at the other single-stranded regions, which suggests that the catalytic Ce species is strictly localized next to the target phosphodiester linkage. No decrease in the reaction rate is observed upon introduction of scavengers for hydroxyl radicals (such as DMSO or MeOH) or singlet oxygen (such as NaN(3)) to the system; this indicates that the reaction proceeds via a hydrolytic pathway. Any significant contribution by an oxidative pathway is further ruled out by the observation that nucleosides remain intact after incubation with Ce(IV)/EDTP complex for extended periods.