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1.
The determination of iron(II) with 1,10-phenanthroline in aqueous solutions was carried out exemplarily by thermal lens spectrometry. The peculiarities of analytical reactions at the nanogram level of reactants can be studied using this method. Under the conditions of the competing reaction of ligand protonation, the overall stability constant for iron(II) chelate with 1,10-phenanthroline was determined at a level of n x 10(-7) mol L(-1), logbeta3 = 21.3+/-0.1. The rates of formation and dissociation of iron(II) tris-(1,10-phenanthrolinate) at a level of n x 10(-8) mol L(-1) were found to be (2.05+/-0.05) x 10(-2) min(-1) and (3.0+/-0.1) x 10(-3) min(-1), respectively. The conditions for the determination of iron(II) with 1,10-phenanthroline by thermal lensing were reconsidered, and ascorbic acid was shown to be the best reducing agent, which provided minimum and reproducible sample pretreatment. Changes in the conditions at the nanogram level improved both the selectivity and sensitivity of determination. The optimum measurement conditions for thermal lensing were determined not only by the absorption of the analyte and reagents, but also by the background absorption of the solvent. The limits of detection and quantification of iron(II) at 488.0 nm (excitation beam power 140 mW) are 1 x 10(-9) and 6 x 10(-9) mol L(-1), respectively; the reproducibility RSD for the range n x 10(-8)-n x 10(-6) mol L(-1) is 2-5%.  相似文献   

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Thermal behaviour of the complexes [M(phen)3]X2·nH2O has been studied in static air and vacuum atmospheres (where M = Fe(II), Ni(II); phen = 1, 10-phenanthroline; and X = Cl, Br, I, SCN). The intermediate derivatives of the thermal decomposition of these complexes having composition M(phen)2X2 are isolated in the furnace of DTA-TG apparatus under vacuum atmospheric conditions. Structures are assigned to these intermediate complexes on the basis of analytical data, reflectance spectra, magnetic moments and X-ray powder diffraction patterns.  相似文献   

4.
Absorption at the excitation wavelength recovers in a sub-nanosecond, two stage process following bleaching of tris(1,10-phenanthroline) iron(II) by a single picosecond pulse at 530 nm. Absorption coefficients and decay times suggest that a CT and a dd excited state are consecutively occupied before ground state repopulation.  相似文献   

5.
A heat-induced refractive index change is used to increase the sensitivity of the spectrophotometric determination of iron(II) in a dual-beam system. An argon ion laser (514.5 nm) is used as the heating source and the intensity variation of a helium—neon laser (632.8 nm) is measured. The sensitivity is increased 7.3 times compared with spectrophotometry; the detection limit is 3 × 10-7 M.  相似文献   

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The thermal behavior of the Fe(II) iodide mixed complexes with 1,10-phenanthroline and 4,7-disubstituted phenanthrolines in nitrogen atmosphere is investigated.In order to determine to what extent small changes in ligand field symmetries influence the “activation energy” Ea, this energy is determined. The results are discussed in relation to the changes of the σ and π bonds.  相似文献   

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Summary A new procedure has been developed for the colorimetric determination of iron(III). It consists in the reduction of iron (III) in dilute sulphuric acid medium (0.1 to 1.0 N) with an excess of hypophosphite (1100) at room temperature using one or two drops of 0.1% PdCl2 solution as catalyst, and then complexing the reduced iron with 1.10-phenanthroline.Iron (III) can also be reduced with phosphite using the PdCl2 catalyst and boiling for 5 to 10 min on a hot plate. The molar concentration of phosphite is preferably kept 500 times that of ferric ion.
Zusammenfassung Es wurde ein neues Verfahren zur colorimetrischen Bestimmung von Eisen(III) ausgearbeitet. Dabei wird das Eisen in verd. Schwefelsäure (0,1–1,0 n) mit einem Überschuß von Hypophosphit (1100) bei Zimmertemperatur unter Verwendung von ein oder zwei Tropfen 0,1%iger PdCl2-Lösung als Katalysator reduziert und anschließend das zweiwertige Eisen mit 1,10-Phenanthrolin umgesetzt.Eisen(III) kann auch mit Phosphit reduziert werden, wenn man ebenfalls PdCl2 als Katalysator verwendet und 5–10 min erhitzt. Die molare Konzentration des Phosphits soll dabei das 500fache von der des Eisens betragen.
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10.
A study was made to establish proper conditions for the selective determination of Fe(II) by the 1,10-phenanthroline method in the presence of large amounts of Fe(III). It was shown that fe(III) is effectively masked by fluoride. The pH of the solution to be masked should be below 2.5 in order to prevent acceleration by the fluoride of aerial oxidation of Fe(II).  相似文献   

11.
Poe DP  Diehl H 《Talanta》1974,21(10):1065-1071
Tris(4,7-dihydroxy-1,10-phenanthroline)iron(II) reacts rapidly and quantitatively with dissolved oxygen in alkaline aqueous solution. In ammoniacal solution, the reaction is accompanied by the disappearance of the intense red colour of the iron(II) compound, which gives way to the pale gray, slightly-dissociated ion tris(4,7-dihydroxy-1,10-phenanthrolinefiron)(III). By measurement of the absorbance of a solution containing the ferrous compound before and after the injection of an oxygen-containing solution, the concentration of dissolved oxygen in the sample can be accurately determined in the range 1-20 ppm.  相似文献   

12.
Infrared spectroscopic studies of 1:1 and 1:2 complexes of lead(II) bromide and lead(II) iodide with 1,10-phenanthroline were reported. Vibrational assignments are made by comparison to reported spectra of the uncomplexed 1,10-phenanthroline molecule. Small shifts of the ligand vibrational bands are characteristic of the complexes.  相似文献   

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The stability constants for copper(I) chelate with 2,9-dimethyl-1,10-phenanthroline are determined by thermal lensing, and the advantages over spectrophotometric determination of stability constants are shown. Changes in the photometric reaction when moving from the microgram to the nanogram level of reactants are discussed. The conditions for the thermal-lens determination of copper are optimized. The limit of detection of copper is 3x10(-8) mol dm(-3), and the linear calibration range 1x10(-7)-1x10(-5) mol dm(-3).  相似文献   

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Two types of mixed-ligand complexes, i.e. [M(phen)2 (dip)]2+ and [M(phen)(dip)2]2+ (M = iron(II) and nickel(II); phen = 1,10-phenanthroline and dip = 4,7-diphenyl-1,10-phenanthroline) have been prepared from their related tris-complexes, [M(phen)3]2+ by ligand substitution, and isolated by semi-preparative HPLC. Elemental and chromatographic analyses confirm the purity of the isolated complexes while u.v./vis and i.r. spectra were used to identify and characterize them. 1H-n.m.r. and room temperature Mössbauer spectra of the iron(III) complexes were also measured and the results are discussed. In addition, our preliminary results on hypochromicity in the MLCT band and circular dihroism (CD) emerging in the u.v./vis region upon addition of CT(calf thymus)-DNA to the racemic complexes indicated that the iron(II) mixed-ligand complexes interact with CT-DNA.  相似文献   

17.
Summary Kinetic parameters are reported for aquation of the tris-(4-methyl-1,10-phenanthroline) iron(II) [Fe(4-Mephen)3]2+, cation and for its reactions with hydroxide, cyanide, and peroxodisulphate. Activation volumes have been determined for the two last-named reactions; they reflect the importance of solvation changes in transition state formation.  相似文献   

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The electrochemical behavior of 5-amino-1,10-phenanthroline and tris[5-amino-1,10-phenanthroline]-iron(II) at carbon paste, glassy carbon, and platinum electrodes is reported. The iron complex undergoes electrochemically induced oxidative polymerization from acetonitrile solutions and the resulting polymers are very stable. Charge transport through the polymer films occurs with a charge transfer diffusion coefficient, Dct, equal to 3.1 × 10−8 cm2 s−1 corresponding to an electron self-exchange rate of 5.2×107M−1 s−1. The activation energy and the entropy change for the charge transfer diffusion process are (approximate values) 32.0 ± 0.12 kJ mol−1 and −24.7 ± 0.4 J K−1 mol−1, respectively.  相似文献   

20.
By the example of the analytical system based on the reaction of bismuth with iodide, it is shown that thermal lens spectrometry can be used for studying changes in analytical reactions at the nanogram level of reactants. The stability constants of bismuth(III) iodides at the concentration level are found. The solubility constants of iodides of metals interfering with bismuth determination are estimated. It is shown that the due regard to the new conditions could enhance the sensitivity and selectivity of determination.  相似文献   

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