[en] A plot of Moessbauer isomer shift and quadrupole splitting for monosubstituted ferrocyanides gave straight line correlation. This has been used for predicting the sign of electric field gradient depending on the π-bonding nature of the substituted ligand. (F.G.)

No abstract available

[en] Moessbauer parameters of ferrocyanides of the type M₄sup(III)[Fesup(II)(CN)₆]₃xxH₂O (where M = Al, As, Sb, Bi) are reported. As a result of the dehydration of the ferrocyanides the isomer shift value increases. Antimony ferrocyanide has an absorption of 20.8%, which can be used for calibration in single line absorption spectrum. The value of isomer shift in the case of bismuth ferrocyanide is higher due to lesser number of coordinated water molecules. (author)

No abstract available

[en] In the present work the sign of Hsub(int) was measured for Ni₃[Fe(CN)₆]₂. The polycrystalline absorber was placed in an external longitudinal magnetic field of a superconducting solenoid. The temperature of the sample, 4.2K, was sufficiently below the Curie point Tsub(c)=19.5K and the magnitude of Hsub(ext) used was strong enough to orient the magnetic domains, also stronger than any possible induced fields. The Moessbauer experimental spectra are presented amounts to 265+-10 kOe, in agreement with earlier data. The observed expansion of the Zeeman pattern in the external field signifies the positive sign of Hsub(int)

[en] Detailed Moessbauer spectra of ⁵⁷Fe in the iron storage protein, ferritin, in the temperature range between 250 and 280 K reveal a first-order phase transition with a thermal hysteresis loop of 7 K width. While the temperature is raised from 90 K to 271 K, Moessbauer spectra composed of a narrow line quadrupole doublet, typical for solids, are observed. Above this temperature, each spectrum is composed of the narrow line subspectrum and a broad line subspectrum whose relative intensity increases with temperature. The intensity of the narrow line subspectrum decreases by a factor of five at the critical temperature and thus shows a large increase in the mean square displacements at T_up=271 K. While decreasing the temperature, the bounded diffusive motions, expressed in the spectra by the coexistence of the narrow and broad lines, survive down to T_down=264 K, where again the spectral shapes and areas undergo a discontinuous jump. The narrow line subspectrum increases in intensity and the broad line subspectrum disappears. These phenomena may be understood in terms of supercooling of the water in the free channels and in the cavity of the ferritin molecule. (orig.)

No abstract available

[en] Full text: The Moessbauer spectra of Prussian Blue have traditionally been fitted using one singlet and one doublet, to fit the ferrocyanide and ferric iron sites. However, it is widely accepted in the literature that there are several possible configurations for the ferric site, and each of these should be fitted individually to obtain a meaningful fit. According to the literature, there are two possible Prussian Blue structures, Insoluble Prussian Blue (IPB), Fe³⁺₄[Fe^II(CN)₆]₃.14H₂0, and Soluble Prussian Blue (SPB) KFe³⁺[Fe^lI(CN)₆]. In IPB there are ten uniquely different coordinations for the ferric site due to many different arrangements of cyanide and water ligands. In SPB there is a more continuous range of ferric sites, due to the presence of potassium ions in voids throughout the cubic lattice. A variety of samples have been prepared which, according to the literature, should have produced three IPB and three SPB samples. However, all the samples appear to be best represented by the IPB structure. A number of different methods have been used to fit the Moessbauer spectra of Prussian Blue, using both Gaussian and Voigtian line shapes. The point charge model has been used to calculate the quadrupole splitting for each ferric site, and the corresponding isomer shifts have been estimated from the partial isomer shifts for each ligand. These theoretical parameters have been used to obtain excellent fits to a range of Prussian Blue samples. Details will be given of improvements in our knowledge of the structure of these well known, but crystallographically complex compounds

[en] The kinetics, mass transport, and double layer features of the reversible ferro-ferricyanide redox couple were studied through intermodulated differential immittance spectroscopy (IDIS). The system is fully characterized by the quantification of the electron-transfer parameters (α, and i_0), the diffusion coefficients of the redox couple (D_r_e_d and D_o_x), together with the double layer capacitance and its variation (C_d_l and Δ_d_l) at the open circuit potential, without the need of assuming a particular dependence of these parameters on the potential. The result was achieved by implementing the mathematical framework developed previously in a fitting procedure, which takes into account simultaneously the impedance spectrum and several differential immittance spectra of the system

[en] Two simple and sensitive spectrophotometric methods for the determination of tinidazole in pure form and in dosage forms are described. Both methods are based on redox reactions and use Folin-Ciocalteu (Method A) and ferric ferricyanide (Method B) as chromogenic agents. Method A is based on the measurement of blue coloured species (max: 700nm) produced when the drug is reacted with Foin-Ciocalteu reagent in alkaline medium, whereas the method B involves treating the drug with Iron (III) in acid medium and subsequent interaction of iron (II) with ferricyanide to form Prussian blue measurable at 760nm. The working conditions of both methods have been optimized. Regression analysis of Beer's Law plots showed good correlation in the concentration ranges 5-50 and 5-40 ug ml for methods A and B, respectively. The apparent molar absorptivity and Sandell sensitivity values are calculated to be 5.02 x 1000 and 3.36 x 1000l mol cm, and 69.15 and 103.45 ng cm, respectively, for methods A and B. Detection and qualification limits for both methods are calculated. The methods were successfully applied to the determination of tinidazole in bulk drug and its formulations. Excipients used as additives in formulations did not interfere. Statistical treatment of experimental result indicates that the accuracy and precision of the methods are analytically acceptable. The validity of methods was evaluated by parallel determination by an established procedure, and by recovery studies. (author)