Adel F. Shoukry

Ionization of some derivatives of benzamide, oxamide and malonamide in DMF–water mixture

The ionization of six compounds of bis-phenolic amides was studied spectrophotochemically in DMF-water mixture. The compounds showed two pK(a) values in the range of 5.97-7.32 for pK(a(1)) and 7.61-8.44 for pK(a(2)). The obtained values of K(a) were normalized using the distribution diagrams of the different species and found to be in the range of 5.81-7.42 for pK(a(1)) and 7.48-8.27 for pK(a2).

Halogen-free ionic liquid as an additive in zinc(II)-selective electrode: surface analyses as correlated to the membrane activity.

Two conventional Zn(II) polyvinyl chloride (PVC) membrane electrodes have been prepared and characterized. They were based on dibenzo-24-crown-8 (DBC) as a neutral carrier, dioctyl phthalate (DOP) as a plasticizer, and potassium tetrakis (p-chlorophenyl) borate, KTpClPB or the halogen-free ionic liquid, tetraoctylammonium dodecylbenzene sulfonate [TOA][DBS] as an additive. The use of ionic liquid has been found to enhance the selectivity of the sensor. For each electrode, the surfaces of two membranes were investigated using X-ray photoelectron, ion-scattering spectroscopy and atomic force microscopy. One of the two membranes was conditioned by soaking it for 24 h in a 1.0×10(-3) M Zn(NO(3))(2) solution and the second was soaked in bi-distilled water for the same interval (24 h). Comparing the two surfaces indicated the following: (a) the high selectivity in case of using [TOA][DBS] as an additive is due to the extra mediation caused by the ionic liquid and (b) the working mechanism of the electrode is based on phase equilibrium at the surface of the membrane associated with ion transport through the bulk of the membrane.

New tetradecyltrimethylammonium-selective electrodes: surface composition and topography as correlated with electrode's life span.

Two conventional plastic membrane electrodes that are selective for the tetradecyltrimethylammonium cation (TTA) have been prepared. The ion exchangers of these sensors were the ion associate, TTA-PT, and the ion aggregate, TTA-PSS, where PT and PSS are phosphotungstate and polystyrene sulfonate, respectively. The following performance characteristics of the TTA-PT- and TTA-PSS-containing electrodes were found: conditioning time of 30 and 20 min; potential response of 58.2 and 61.1 mV/TTA concentration decade; rectilinear concentration ranges of 2.0 × 10(-5)-5.0 × 10(-2) and 1.5 × 10(-5)-7.9 × 10(-2) mol L(-1); average working pH ranges of 4.0-10.5 and 3.8-10.7; life spans of 20 and 28 weeks, and isothermal temperature coefficients of 4.44 × 10(-4) and 6.10 × 10(-4)V/°C, respectively. Both electrodes exhibited high selectivity for TTA with an increasing number of inorganic and quaternary ammonium surfactant cations. These electrodes have been successfully applied to assay an antiseptic formulation containing TTA. Surface analyses using electron microscopy and X-ray photoelectron spectroscopy were used to determine the cause of the limited life span of plastic membrane electrodes.

Homogeneous precipitation at solid/solution interface as a novel chemical route for synthesis of nanoparticles: application to Cd(II) and Pb(II) sulfides

ABSTRACT Nanoparticles of CdS and PbS were prepared by a novel method in which a sparingly soluble salt of the metal is brought into contact with the preparation solution mixture, without mixing, to introduce Cd2+ or Pb2+ ion into the medium at infinitesimal doses. The aqueous solution mixture contained n-heptane; thioacetamide, as sulphide ion precursor; cetyltrimethylammonium bromide (CTAB), as capping agent; and n-butanol, as co-surfactant. At the solid/solution interface CTAB-capped nanometal sulphide is formed through a metathesis reaction in extreme dilute medium. UV-visible, FTIR, and X-ray diffraction spectroscopy, as well as transmission electron microscopy were used to characterise the nanoparticles. The results showed that in solution, the diameters of the prepared CdS and PbS are 2.67 and 1.87 nm, respectively. In crystalline form, the corresponding diameters are 3.8–6.6 nm, and 6.88–13.9 nm, respectively. The crystalline structure of CdS is cubic or hexagonal, while that of PbS is face-centred cubic. The FTIR studies proved that CTAB acted as a capping agent of the investigated nanoparticles.

Depth profiling X-ray photoelectron spectroscopy and atomic force microscopy of Cd(II)- and Pb(II)-selective electrodes based on nano metal sulfides

This research involved constructing and studying plastic membrane Cd(II)- and Pb(II)-ion selective electrodes of the coated wire type based on nanoparticles of CdS and PbS as ionophores, respectively. The electrodes exhibited average linear concentration ranges of 1.0 × 10−6 to 1.0 × 10−2 and 9.6 × 10−7 to 1.0 × 10−2 M, average detection limits of 8.6 × 10−7 and 5.8 × 10−7 M, pH ranges of 2.2–5.8 and 2.9–5.9, and average calibration graph slopes of 28.56 and 28.81 mV per concentration decade, respectively. Both electrodes showed high selectivity towards many inorganic cations. Depth profiling X-ray photoelectron spectroscopy of fresh and expired membranes proved that: (a) the nanoparticles were homogeneously dissolved in the polymeric network and (b) the limitation of the life span of the plastic membrane was due to leaching of the active ingredient from the membrane surface to the bathing solution. The topography of fresh, active, and expired membranes as imaged by atomic force microscopy revealed the formation of a gel layer at the surface of the active electrode and drastic deformation of the expired membranes surface.