Aromatic acids and creatinine, an important blood metabolite, form well-defined crystalline ionic complexes. Their supramolecular architecture is formed not only by simple proton transfer and ionic interaction but also by other very important noncovalent interactions, especially the hydrogen bonds. The supramolecular behavior of the complexes is varied with the acidity and structural difference of aromatic acids. Creatinine interestingly generated creatine monohydrate during crystallization of creatinine with glacial acetic acid and the supramolecular array of creatine monohydrate is also reported.

Recognition of creatinine by weak aromatic acids in solid phase along with their supramolecular network

Complexation of Creatinine by Synthetic Receptors

The applicability of 2-hydroxybenzaldehyde benzoylhydrazone (2-HBBH) for determining Cd(II), Cu(II), Pb(II) and Bi(III) ions by adsorptive cathodic stripping voltammetry was studied. The sensitivity of metal reduction peak currents was highly enhanced with the addition of 2-HBBH to metallic solutions, showing the adsorptive characteristics of the complexes. Variable factors affecting the response (mainly: the influences of pH, supporting electrolyte and deposition potential on selectivity and sensitivity) were investigated. Limits of detection suitable for trace analysis were obtained: 0.28 μg L−1 for Cd(II) at pH 10; 0.026 μg L−1 for Pb(II) at pH 9; 0.285 μg L−1 for Bi(III) at pH 8 and 0.051 μg L−1 for Cu(II) at pH 9.5. Simultaneous determinations of two groups of elements, consisting of Cd(II)-Pb(II)-Cu(II) and Cd(II)-Pb(II)-Bi(III), at pH 9.5 and 9, respectively, were described with good resolution and sensitivities. Metals were quantified at concentrations in the range from 0.5 to 14 μg L−1. The RSD at a concentration level of 5 μg L−1 of metal was 4.28% for Cd(II), 2.99% for Pb(II), 4.82% for Bi(III) and 1.35% for Cu(II). The method was applied to the simultaneous determination of metals in certified reference water (TMDA-62) and in synthetic water samples with satisfactory results.

Applicability of 2-hydroxybenzaldehyde benzoylhydrazone in the determination of trace metals by adsorptive cathodic stripping voltammetry: relevancy of simultaneous determinations.

The differential pulse polarographic (DPP) and voltammetric (DPV) behaviour of di-2-pyridyl ketone benzoylhydrazone (DPKBH), has been investigated over a wide pH range (2.1–11.5). The effect of various operational parameters on the reduction current are discussed and the mechanism of the electrode reaction is also included. Both methods DPP and DPV are applied for the analytical determination of this reagent and the detection limits are found to be 1.24 μmol/l and 0.86 μmol/l, respectively. The DPP behaviour of DPKBH in the presence of Pb(II), Cd(II) and Cu(II) is studied and the behaviour of the Cu(II)-DPKBH complex is fully investigated. The voltammetric determination of Cu(II), based on the accumulation of its complex at the hanging mercury drop electrode, is described. Statistical analysis of the calibration curve data is included.

Differential pulse polarography and voltammetry of di-2-pyridyl ketone benzoylhydrazone

The polarographic behaviour of 3-(2′-thiazolylazo)-2,6-diaminopyridine (2,6-TADAP) has been studied in aqueous buffer solutions and aqueous-ethanol mixtures of different pH's using DC and DP polarographic methods The reduction of the azo linkage takes place via two electrons in both aqueous and aqueous-ethanol mixtures The linear relationship between the current and 2,6-TADAP concentration allowed the polarographic determination of 2,6-TADAP over a wide concentration range The values of the adsorption parameters in the presence of both Triton X-100 (non-ionic) and a new non-ionic surfactant, nonylphenol polyoxypropylene polyoxyethylene (NPE 1800) have been computed The kinetic parameters of the electrode reaction have been calculated

Polarographic behaviour of 3-(2'-thiazolylazo)-2,6-diaminopyridine using DC and differential pulse polarography

The polarographic behaviour of salicylidenebenzohydrazide (SBH) at a dropping-mercury electrode was studied in aqueous Britton–Robinson buffers containing 40% ethanol. The polarograms consist each of one wave in acidic medium. The height of the wave decreases and its E½ shifts to more negative potentials with increasing pH until it diminishes completely at pH > 10.7. At pH values > 7.2 a second wave appears, the height of which increases with pH and becomes developed at pH values > 10.7. In acid solutions 4-electrons are consumed in the reduction of CN. The second wave is attributed to the reduction of salicylaldehyde which is formed from the hydrolysis of the hydrazide. The effect of pH on the limiting current and E½ as well as the reduction mechanism are discussed. The kinetic parameters of the electrode reaction are also determined.

Yassein M. Temerk

Papers

Polarography of salicylidenebenzohydrazide in solutions of varying pH at a dropping-mercury electrode: effect of hydrogen bonding