Visible absorption spectra of the 4f electron transitions of neodymium, praseodymium, holmium and erbium complexes with fleroxacin and their analytical application.

The absorption spectra of the 4f electron transitions of neodymium, praseodymium, holmium and erbium complexes with fleroxacin in the presence of cetylpyridinium chloride were studied by normal and derivative spectrophotometry. Their molar absorptivity at the maximum absorption bands are about 5.3 (at 571 nm) times greater for neodymium, 2.8 (at 483 nm) times greater for praseodymium, 12.6 (at 448.5 nm) times greater for holmium and 9.7 (at 519 nm) times greater for erbium than those in the absence of complexing agents. The second-derivative spectrum is used both to eliminate the interference from other rare earths and to improve the sensitivity. Beer's law is obeyed from 3.0 - 70 microg ml(-1) for neodymium and holmium, from 6.0 - 70 microg ml(-1) for erbium, and from 12.0 - 70 microg ml(-1) for praseodymium. The relative standard deviations are 1.9% and 1.5% for 7.5 microg ml(-1) of neodymium and holmium, and 2.1% and 1.6% for 15.0 microg ml(-1) of praseodymium and erbium, respectively. Their detection limits (signal-to-noise ratio = 2) are 3.2 microg ml(-1), 1.3 microg ml(-1), (1.1) microg ml(-1) and 2.5 microg ml(-1) for praseodymium, neodymium, holmium and erbium, respectively. A new system for the simultaneous determinations of the praseodymium, neodymium, holmium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.     

Determination of neodymium, holmium and erbium in mixed rare earths by norfloxacin

Norfloxacin (NFX) is proposed as reagent for the derivative spectrophotometric determination of neodymium, holmium and erbium in mixed rare earths. The absorption spectra of 4f electron transitions of the systems of neodymium, holmium and erbium complexes with norfloxacin in presence of cetylpyridinium chloride were studied by normal and derivative spectra. The absorption bands found normally at 575 nm for neodymium, 450 nm for holmium and 523 nm for erbium were enhanced markedly. Using the second derivative spectrum, Beer’s Law is obeyed from 5.0 × 10^–5∼ 2.5 × 10^–4 mol dm^–3 for neodymium, holmium and erbium. The relative standard deviations are 1.0, 1.4 and 1.1% for 6.9 × 10^–5 mol dm^–3 of neodymium, 6.1 × 10^–5 mol dm^–3 of holmium and 6.0 × 10^–5 mol dm^–3 of erbium, respectively. A method for the direct determination of neodymium, holmium and erbium in mixtures of rare earth elements with good accuracy and selectivity, is described. Received: 18 December 1997 / Revised: 23 February 1998 / Accepted: 26 February 1998     

Determination of neodymium, holmium and erbium in mixed rare earths by norfloxacin

Norfloxacin (NFX) is proposed as reagent for the derivative spectrophotometric determination of neodymium, holmium and erbium in mixed rare earths. The absorption spectra of 4f electron transitions of the systems of neodymium, holmium and erbium complexes with norfloxacin in presence of cetylpyridinium chloride were studied by normal and derivative spectra. The absorption bands found normally at 575 nm for neodymium, 450 nm for holmium and 523 nm for erbium were enhanced markedly. Using the second derivative spectrum, Beer’s Law is obeyed from 5.0 × 10^–5∼ 2.5 × 10^–4 mol dm^–3 for neodymium, holmium and erbium. The relative standard deviations are 1.0, 1.4 and 1.1% for 6.9 × 10^–5 mol dm^–3 of neodymium, 6.1 × 10^–5 mol dm^–3 of holmium and 6.0 × 10^–5 mol dm^–3 of erbium, respectively. A method for the direct determination of neodymium, holmium and erbium in mixtures of rare earth elements with good accuracy and selectivity, is described. Received: 18 December 1997 / Revised: 23 February 1998 / Accepted: 26 February 1998     

Derivative Spectrophotometric Determination of Nd, Ho and Er in Rare Earth Mixtures with 1-Ethyl-6,8-difluoro-7-(3-methyl-1-piperazinyl)-4-oxo-1,4-dihydro-3-quinoline carboxylic acid

 The second derivative spectrophotometric method has been developed as a procedure for the determination of neodymium, holmium and erbium in mixed rare earths. It was found that the 1-ethyl-6, 8-difluoro-7-(3-methyl-1-piperazinyl)-4-oxo-1,4- dihydro-3-quinoline carboxylic acid forms stable complexes with neodymium, holmium and erbium ions in the pH 9.2–10.5 range. In the second derivative spectra the optimum analytical signals for neodymium, holmium and erbium are at 576.2 (+)−574.5 (−)nm, 444.2 (+) −447.8 (−)nm and 516.0 (+) −517.2(−)nm, respectively. Beer’s law is obeyed from 5.0×10⁻⁵ M to 2.5×10⁻⁴ M of neodymium, holmium and erbium. The quantification limits (10 Sb) were 1.2×10⁻⁵ M for Nd, 9.7×10⁻⁵ M for Ho and 3.0×10⁻⁶ M for Er. Received April 22, 1998. Revision March 8, 1999.     

Absorption Spectra of the 4f Electron Transitions of the Nd, Ho and and Er Complexes with 1-Cyclopyropyl-6-fluoro-1,4-dihydro-7- (4-ethyl-1-piperazinyl)-4-oxo-3-quinoline Carboxylic Acid Hydrochloride in the Presence of TX-100

The tripositive rare earth metal ions show comparatively little tendencies to form complexes with a variety of normally powerful coordinating agents due to their peculiar electronic configurations. However, certain chelating groups, notably the β-diketones1,2 and 8-quinolinols3,4, are capable of overcoming this difficulty through the formation of inner complex compounds. 1-Cyclopropyl-6-fluoro-1,4-dihydro-7-(4-ethyl-1-piperazinyl)-4-oxo-3-quinoline carboxylic acid hydrochloride (NN…     

Simultaneous determination of neodymium, erbium and holmium in rare earth mixtures with 2-phenyltrifluoroacetone and octylphenol poly(ethyleneglycol) ether by third-derivative spectrophotometry

The complexes of the rare earth metals with 2-phenyltrifluoroacetone in the presence of TX-100 are reported. The characteristic absorbances of neodymium, holmium and erbium complexes can be increased by factors of 8.5, 31 and 15 respectively, compared to those of the cholrides. The third-derivative spectra have been used to eliminate the interference of cerium, and the sensitivities are increased again by factors of 7.4, 5.5 and 6.5. A method for the direct determination of neodymium, erbium and holmium in rare earth mixtures is proposed.     

Spectrophotometric study and analytical application of rare-earth Tiron complexes-II Determination of europium

The absorption spectra of europium-Tiron complexes in aqueous solution have been measured from 340 to 600 nm. The absorbance at 390 and 420 nm follows Beer's law up to 0.8 mg ml (pH 6.2-6.6). Other rare earths except for cerium(III) did not interfere. The interference of cerium could be removed by addition of ascorbic acid. The combining ratio of Tiron to europium has been found to be 1:1.     

BODIPY chromophores as efficient green light sensitizers for lanthanide-induced near-infrared emission

A new boron dipyrromethene (BODIPY) modified 8-hydroxylquinoline ligand (8-HOQ-BODIPY) is synthesized for the sensitization of near-infrared emission of lanthanide(III) ions. The BODIPY unit, as revealed by single-crystal X-ray diffraction analysis, aligns almost perpendicularly to the 8-HOQ unit. The ligand exhibits strong absorption at ~506 nm and fluorescence at 510 nm in organic solvents with quantum yields ranging from ~0.45 in dichloromethane to 0.015 in ethanol. It forms stable ytterbium(III), erbium(III) and neodymium(III) complexes with 3:1 ligand-to-metal molar ratios. Upon excitation (~522 nm), the neodymium(III) and erbium(III) complexes emit weakly at 1060 and 1382 nm, respectively, whereas the ytterbium(III) complex exhibits strong emission at 976 and 1003 nm. The results demonstrate the potential of BODIPY dyes as efficient and robust visible light sensitizers for lanthanide-based NIR emitters in medical diagnosis.     

Spectrophotometric study and analytical applications of lanthanide-kojic acid complexes Direct determination of Nd, Ho and Er in mixtures of rare earths

The complexes of the rare-earth metals with kojic acid in weakly alkaline solution are reported. The characteristic absorbances of neodymium, holmium and erbium can be increased by factors of 4.3, 11.0 and 6.4 respectively, compared with those of the chlorides. The third-derivative spectra have been used to eliminate the interference of Ce, La and Y, and the sensitivities are again increased, by a factor of 6-9.     

Study of the absorption spectra of the 4f electron transition of the Nd and Er complexes with 2-isobutylformyl-1,3-dione-indane in the presence of TX-100 and its analytical application

The absorption spectra of 4f electron transitions of the systems of neodymium and erbium with 2-isobutylformyl-1,3-dione-indane and TX-100 have been studied by normal and derivative spectrophotometry. Their molar absorptivities at the maximum absorption bands are about 7.2 (at 571 nm) times greater for neodymium and 13.1 (at 519 nm) times greater for erbium than those in the absence of the complexing agents. Use of second derivative spectra both eliminates the interference from other rare earths and increases the sensitivity from neodymium and erbium. Beers law is obeyed from 020 g/ml for neodymium and 025 g/ml for erbium. The relative standard deviations are 1.2% and 1.6% for 5.0 g/ml of neodymium and 8.0 g/ml of erbium, respectively. The detection limits (signal-to-noise ratio=2) are 0.14 g/ml and 0.20 g/ml. A method for the direct determination of neodymium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.     

Structural studies of uranium and thorium complexes with 4,5-dihydroxy-3,5-benzenesdisulfonate (Tiron) at low and neutral pH by X-ray absorption spectroscopy

We have determined the structure of uranyl, UO(2)(2+), and Th(4+) complexes formed in aqueous solution with 4,5-dihydroxy-3,5-benzenedisulfonate (Tiron) as function of pH and concentration. At equimolar concentrations of 0.05 M UO(2)(2+) and Tiron, the predominant species was found to be aqueous uranyl at pH = 2.0. At pH = 6.0, the formation of a 3:3 UO(2)(2+):Tiron trimer (proposed in earlier studies) was observed. In this structure, bidentate catecholate complexation to Tiron as well as oxygen bridging between uranyl units is detected. Th(4+) structural changes were observed both as a function of pH and Th:L (L = Tiron) ratio. At Th:L = 1:1 and pH = 1.4, a monomeric complex is observed with each Th center complexing monodentate to approximately 2 sulfonate functional groups. At pH 4.0 similar sulfonate ligation is observed along with oligomer formation. At pH 6.0 thorium hydrolysis products are detected, with little evidence for inner-sphere Tiron coordination. When the Th:L is changed to 1:2 at pH = 6.0, a stable oligomeric complex is formed that dominates the speciation for Th:L ratios up to 1:5. This complex is characterized by bidentate catechol and monodentate sulfonate ligation to Tiron along with oxygen bridging between Th(4+) atoms and is consistent with the formation of the 2:3 Th:L polymeric species proposed from earlier work. At a Th:L ratio of 1:10, Th(4+) complexation is dominated by bidentate catechol ligation and the formation of a monomeric Th(Tiron)(x) species, where x > or = 2.     

UV and fluorescence spectral changes induced by neodymium binding of N,N'-ethylenebis[2-(o-hydroxyphenolic)glycine] and N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N' diacetic acid

In 0.01 M 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (Hepes), pH 7.4 and room temperature, the binding of neodymium to N,N'-ethylenebis[2-(o-hydroxyphenolic)glycine] (EHPG), or N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N' diacetic acid (HBED) had been studied from 210 to 330 nm by means of difference UV spectra. Two peaks at 240 and 292 nm appear in difference UV spectra after neodymium binding to EHPG or HBED. The 1:1 stable complex can be confirmed from spectral titration curves. The molar extinction coefficient of Nd-EHPG and Nd-HBED complexes are Deltaepsilon(Nd-EHPG)=(12.93+/-0.21) x 10(3)cm(-1)M(-1), Deltaepsilon(Nd-HBED)=(14.45+/-0.51) x 10(5)cm(-1)M(-1) at 240 nm, respectively. Using EDTA as a competitor, the conditional equilibrium constants of the complexes are logK(Nd-EHPG)=11.89+/-0.09 and logK(Nd-HBED)=12.19+/-0.15, respectively. At the same conditions, fluorescence measurements show that neodymium binding to EHPG leads to a quenching of the fluorescence of EHPG at near 310 nm. However, there is no obvious fluorescence change of HBED at 318 nm with the binding of neodymium to HBED.     

DIRECT DETERMINATION OF NEODYMIUM AND ERBIUM IN RARE EARTH MIXTURE BY DERIVATIVE SPECTROPHOTOMETRY

The absorption spectra of 4f electron transitions of the complexes of neodymium and erbium with 8-hydroxyquinoline-5-sulphonic acid in the presence of diethylamine and ethanol have been measured by normal and third-derivative spectrophotometry. Their molar absorptivities are 70.7 l.mol~(-1).cm~(-1) for Nd and 62.5 l.mol~(-1).cm~(-1) for Er. They are 7.6 times and 14.9 times greater than those of corresponding chlorides, respectively. Use of the third-derivative spectra both eliminates the interference of Ce(Ⅳ) and increases the sensitivity for Nd and Er. Beer,s Law was obeyed from 0-10 ug/ml of Nd and Er. The method has been applied to the determination of neodymium and erbium in rare earth mixtures.     

Colorimetric recognition of Cu(II) by (2-dimethylaminoethyl)amino appended anthracene-9,10-diones in aqueous solutions: deprotonation of aryl amine NH responsible for colour changes

Chromogenic receptors 2 and 3 undergo distinct colour changes from magenta to blue on gradual addition of Cu(II) and can be used as colorimetric probes for spectrophotometric and visual analysis of Cu(II) in the presence of biological metal ions Na(I), K(I), Mg(II), Ca(II), Fe(II), Zn(II) etc. in aqueous solution (methanol-water 1 : 1 v/v). On addition of Cu(II), both 2 and 3 exhibit a bathochromic shift of Delta lambda(max) = 114 nm for 2 and Delta lambda(max)= 150 and 265 nm for receptor 3. The protonation constants and formation constants of Cu(II) complexes of receptors 2 and 3 (at pH 7) and the effect of pH on formation of these complexes has been determined by the combination of UV-vis-pH titrations of receptors 2 and 3 and their Cu(II) complexes. These results and the emergence of only one peak at 610 nm for 2 and two distinct absorption peaks at 715 and 800 nm for 3 on addition of Cu(II) unambiguously point to mono- and di-deprotonation for 2 and 3, respectively.     

The determination of fluorine in rare earth fluorides by high temperature hydrolysis

The technique of pyrohydrolysis has been applied to the determination of fluorine in the fluorides of scandium, yttrium, and the lanthanons. These fluorides have been divided into two classes according to their rate of hydrolysis. Lutetium, ytterbium, cerium(III), scandium, gadolinium, terbium, dysprosium, holmium, erbium, and thulium florides can be hydrolyzed in 30 min or less. Yttrium, lanthanum, praseodymium, neodymium, samarium, and europium fluorides require from 45 to 150 min for complete hydrolysis. Accelerators, such as uranium oxide (U₃O₈), chromium(III) oxide, and a mixture of these oxides have been used successfully to reduce the tune required for quantitative hydrolysis of the fluorides in the latter group. The use of the correct accelerator reduces the hydrolysis time to 30 min or less for all these fluorides except lanthanum, praseodymium and neodymium.     

IR luminescence of neodymium(III) and ytterbium(III) complexes with acylpyrazolones in solutions

Acylpyrazolones (L1–L5) have been synthesized and the conditions of their complexation with neodymium(III) and ytterbium(III) ions in aqueous solutions have been elucidated. The component ratio in the synthesized complexes is Nd(Yb): L = 1: 1. The conditions of excitation and luminescence of the ligands and complexes have been studied. The formation of mixed-ligand complexes upon the introduction of trioctyl- or triphenylphosphine oxide leads to a considerable rise of neodymium and ytterbium. In the presence of 1,10-phenanthroline and bathophenanthroline, competing complexation leads to a 20–70% decrease in luminescence intensity. The introduction of water-miscible organic solvents (30 vol %) decreases the Nd(III) and Yb(III) luminescence intensity by a factor of 9–20.     

Hypersensitivity and its application to structural analysis of lanthanide complexes

Hypersensitivity of the ternary complexes Ln(β-dik)4HMQ(where Ln=Nd, Ho, Er,β-dik=acetylacetonate(AA), dibenzoylmethanate(DBM) and MQ=4-methylquinoline) in acetone solution is studied based on the dynamic coupling model. The structures of these complexes in solution are deduced. Their coordination polyhedrons are all distorted square antiprism. Neodymium complexes have D2 symmetry, while holmium and erbium complexes have exact D2d symmetry.     

Spectrofluorimetric determination of copper(II) by its static quenching effect on the fluorescence of 4,5-dihydroxy-1,3-benzenedisulfonic acid

A spectrofluorimetric method has been developed for the determination of trace Cu(II) in real samples with 4,5-dihydroxy-l,3-benzenedisulfonic acid (Tiron) as a fluorimetric reporter. Tiron is very soluble in water and is a good fluorimetric reagent. However, as Tiron was complexed with Cu(II), the fluorescence intensity decreased proportionally to the concentration of Cu(II) by a static quenching effect. The excitation wavelength and the fluorescence wavelength of Tiron were 294 and 350 nm, respectively, as it was caused by a quenching effect from Cu(II) at pH 8.0. The highest sensitivity was shown at Tiron concentration of 5.0x10(-5) M. To enhance the quenching effect, the Cu(II)-Tiron complex solution was heated up to 80 degrees C for 90 min. As for Cu(II), the interference by Co(II) was very serious, which was eliminated by oxalate ion. The linear response to Cu(II) was shown at the concentration range between 5.0x10(-7) and 1.0x10(-5) M. With this proposed method, the detection limit of Cu(II) was 3.83(+/-0.09)x10(-7) M. Recoveries of Cu(II) in the diluted brass samples and the stream water samples were almost 100%. Based on results from the experiment, this proposed technique could be applied to the practical determination of Cu(II) in real samples.     

Simultaneous determination of neodymium and erbium in rare earth mixture with 5,7-dibromo-8-hydroxyquinoline and TX-100 by third-derivative spectrophotometry

The absorption spectra of 4f electron transitions of the complexes of neodymium and erbium with 5,7-dibromo-8-hydroxyquinoline in the presence of octylphenol poly(ethyleneglycol)ether have been studied by normal and third-derivative spectrophotometry. The proposed method is free of interference of other rare earths. The calibration graphs were linear up to 18 g/ml of neodymium and 21 g/ml of erbium (in the final solution). The derivative molar absorptivities are 395 l.mol^–1.cm^–1 for neodymium and 3421.mol^–1.cm^–1 for erbium. The corresponding values of Sandell's sensitivity were 0.36 and 0.49 g.cm^–1, respectively. The relative standard deviations evaluated from ten independent determinations of 2.5 g/ml of neodymium and erbium are 1.5 and 3.8% for neodymium and 1.8 and 4.1% for erbium in absence and presence of 70 g of lanthanum, respectively. The detection limits (signal to noise ratio=2) are 0.23 g/ml for neodymium and 0.30 g/ml for erbium. The method has been used for the determination of neodymium and erbium in mixed rare earths with satisfactory results.     

Furoin thiosemicarbazone as an analytical reagent for nickel(II), palladium(II) and copper(II)

Furoin thiosemicarbazone (FTS) reacts with Ni(II), Pd(II) and Cu(II) in aqueous medium, giving yellow solutions at pH 9, 6 and 3 respectively. The complexes have absorption maxima at 360 nm for Ni(II) and Pd(II) and 355 nm for Cu(II). At these wavelengths the reagent absorbance is negligible. The molar absorptivities are 1.54 x 10(4) [Ni(FTS)(2)], 1.98 x 10(4) [Pd(FTS)(2)] and 1.45 x 10(4) 1.mole(-1).cm(-1) (CuFTS). Beer's law is valid up to 4, 5 and 3 ppm for Ni, Pd and Cu respectively. The apparent instability constant of the Ni-FTS system is found to be 6.5 x 10(-11), of the Cu-FTS system 7.1 x 10(-7) and of the Pd-FTS system 3 x 10(-12) at the recommended pH values. The effect of various ions is reported.