Hussein M. Abdel-Fattah

A New Metformin Selective Plastic Membrane Electrode Based on Metformin Tetraphenylborate

Abstract A new metformin (Mf) ion selective PVC membrane electrode based on the ion-pair complex of Mf with sodium tetraphenylborate was prepared and its performance characteristics were studied. The electrode exhibited a linear response with a good Nernstian slope over a relatively wide range of concentration. The calibration graph slope was constant for up to 14 days with continuous soaking at 54 mv/ concentration decade at 30°C. Then the slope decreased as the time of soaking increased, reaching 42 mv/decade after 21 days. The changes in pH did not affect the electrode performance within the range 4.0–11.0. The standard electrode potentials were determined at different temperatures and were used to calculate the isothermal coefficient of the electrode (0.0004 V/°C). The electrode showed a very good selectivity for Mf with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were used to determine Mf in pure solutions and in pharmaceutical...

Synthesis, spectral, thermal and magnetic studies of Mn(II), Ni(II) and Cu(II) complexes with some benzopyran-4-one Schiff bases

The Schiff bases of N(2)O(2) dibasic ligands, H(2)La and H(2)Lb are prepared by the condensation of ethylenediamine (a) and trimethylenediamine (b) with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one. Also tetra basic ligands, H(4)La and H(4)Lb are prepared by the condensation of aliphatic amines (a) and (b) with 6-formyl-5,7-dihydroxy-2-methylbenzopyran-4-one. New complexes of H(4)La and H(4)Lb with metal ions Mn(II), Ni(II) and Cu(II) are synthesized, in addition Mn(II) complexes with ligands H(2)La and H(2)Lb are also synthesized. Elemental and thermal analyses, infrared, ultraviolet-visible as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. The structures of copper(II) complexes are also assigned based upon ESR spectra study. All the complexes separated with the stoichiometric ratio (1:1) (M:L) except Mn-H(4)La and Mn-H(4)Lb with (2:1) (M:L) molar ratio. In metal chelates of the type 1:1 (M:L), the Schiff bases behave as a dinegative N(2)O(2) tetradentate ligands. Moreover in 2:1 (M:L) complexes, the Schiff base molecules act as mono negative bidentate ligand and binuclear complex is then formed. The Schiff bases were assayed by the disc diffusion method for antibacterial activity against Staphylococcus aureus and Escherichia coli. The antifungal activity of the Schiff bases was also evaluated against the fungi Aspergillus flavus and Candida albicans.

Synthesis and characterization of tetradentate bis -Schiff base complexes of di- and tri-valent transition metals

The bis-Schiff bases of N2O2 dibasic ligands, H2La and H2Lb are synthesized by the condensation of ethylenediamine (a) and trimethylenediamine (b) with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzo-pyran-4-one. The ligands are characterized using elemental analysis, IR, UV–Vis, 1H-NMR and mass spectroscopy. The ionization constant pKa values are determined spectrophotometrically. The 1H-NMR spectra of the ligands show the presence of phenolic coordinating groups. New complexes of H2La and H2Lb with metal ions Cr(III), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) are synthesized. Elemental analyses, infrared, ultraviolet-visible, electron spin resonance and thermal analysis, as well as conductivity and magnetic susceptibility measurements, are used to elucidate the structures of the newly prepared metal complexes. Thermal degradation studies for some complexes show that the final product is the metal oxide. A square planar geometry is suggested for the Cu(II), Zn(II) (for H2La and H2Lb) and Ni(II) (for H2La) complexes; an octahedral geometry for the Co(II), Cr(III), Fe(III) (for H2La and H2Lb), and Ni(II) (for H2Lb) complexes. The coordination sites are two azomethine nitrogens and two phenolic oxygens in the tetradentate Schiff bases.

Structural studies on new diphenyl formazans and their lanthanide(III) complexes

SummaryPotentiometric, u.v., i.r., n.m.r. and t.g.a. studies have been carried out on 1,5-bis(o-carboxyphenyl)-3-acetyl-formazan and 1-(o-carboxyphenyl-5-(o-hydroxyphenyl)-3-acetylformazan and their complexes with trivalent lanthanide ions. The ionization constants of formazans and the formation constants of their complexes have been determined potentiometrically by the Bjerrum-Calvin method (Irving and Rossotti modification). Complexation has also been studied by a conductimetric titration method.

Construction and performance characteristics of new tetramisole selective plastic membrane electrodes.

New tetramisole (Tm) ion selective PVC membrane electrodes are constructed based on either the ion-pair complex Tm TPB (Electrode I) where TPB is tetraphenylborate or the ion associate Tm(3) PT (Electrode II) where PT is phosphotungstate. The rectilinear concentration ranges of Electrodes I and II are 4 x 10(-5)-10(-2)M (average slope = 55.7 mV/concentration decade) and 5 x 10(-5)-10(-2)M TmCl (average slope = 57.0 mV/concentration decade), at 25 degrees C, respectively. The life time of the two Electrodes I and II are 14 and 49 days of continuous working, respectively. The change in pH does not affect the electrodes performance within the range 3.0-5.5, 3.0-6.0 and 3.0-7.0 for Tm concentrations 10(-2) 5 x 10(-3) and 10(-3)M, respectively. The isothermal coefficients of Electrodes I and II are found to be 0.000667 and 0.001164 V/ degrees C, respectively. The electrodes proved to be highly selective for TmCl towards inorganic cations, sugars and amino acids. The standard addition method and potentiometric titration are used to determine Tm in pure solutions and in tetramisole 10% oral solution. Regeneration process for the exhausted Electrodes I and II is applied successfully by soaking them in a solution of NaTPB and PTA, respectively.

Thermogravimetric studies on lanthanide complexes of new derivatives of 1,5-diaryl-3-acetylformazan

Abstract Solid complexes of two new derivatives of 1,5-diaryl-3-acetylformazan with lanthanide metal ions were prepared and characterized by elemental and thermogravimetric analyses. The suggested formula of the complexes is ML 2 (H 2 O) x · y H 2 O where L = formazan, x = 0–2, y = 1–4 and M = trivalent lanthanide ion. Information about the water of hydration, the coordination chemistry and the thermal stability of these complexes was obtained. A general mechanism for the thermal decomposition of the complexes is suggested. A coordination number of ten is proposed for the lanthanide ions in these complexes which decreases from La to Lu due to the lanthanide contraction.