Vol 73, No 12 (2018)

Ion imprinted polymer (IIP) for copper was synthesized for selective extraction of copper from different samples for analysis using flame atomic absorption spectrophotometry. In the synthesis of ion-imprinted polymer Cu(II) ion (template), 2,2'-bibyridine (ligand) and 4-vinylpyridine (functional monomer) which formed a complex through coordination with Cu(II) ion, ethylene glycol dimethacrylate (cross-linker) and 2,2'-azobisisobutyronitrile (initiator) were used. The ion-imprinted polymer and non-imprinted polymer (NIP) were synthesized via precipitation polymerization process. The synthesized polymers were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. Variables affecting the solid phase extraction of Cu(II) such as pH, initial Cu(II) concentration and time were studied in batch experiments. Quantitative retention of Cu(II) on IIP was achieved at pH 7. The IIP selectivity for copper ion extraction was higher as compared to NIP in the presence of other competing metal ions. The method was successfully applied to the determination of copper in multivitamin tablet, various natural water samples and industrial effluent.

The homologous series of dialkyl phosphonates (C_nH_{2n + 1}O)₂PH=O] (2 ≤ n ≤ 9) (dialkyl phosphites is their commonly used trivial name) was characterized by electron ionization mass spectra and retention indices (RIs) on an RTX-5 standard nonpolar stationary phase. It was established that, in the presence of even one chiral center in the alkyl fragments (for example, in sec-alkanol esters), dialkyl phosphonates were detected in the form of several chromatographic signals due to diastereomers with differences in the retention indices from 4 to 21. The four-coordinated phosphorus atom is the second chiral center. The homologous increments of the retention indices of di-n-alkyl phosphonates (i_RI ± s_RI = 29 ± 9) and esters having one (–4 ± 10) and two (–61 ± 14) branching points in the carbon skeletons of alkyl fragments were evaluated. These values, which were calculated based on data for a limited number of homologues, make it possible to characterize any compounds from the test series. It was found that the relationship М ≈ 0.14(RI – i_RI) + y makes it possible to uniquely determine the molecular weights of analytes according to chromatographic data under the condition of rounding the results to the nearest value of M comparable with y = 12 to the modulus 14 [М ≡ 12(mod14)].

Dopamine and ascorbic acid has been fractionally determined at nickel oxide nanoparticles (nano-NiO_x) modified polycrystalline gold electrode (poly-Au), nano-NiO_x/Au, with high selectivity using voltammetric techniques. Nano-NiO_x/Au electrode, fabricated electrochemically, could resolve the overlapping obtained at the bare poly-Au electrode. Nano-NiO_x/Au electrode was prepared by cycling of potential of Au electrode in diluted Watts bath in the potential range between 0.0 and –1.0 V vs. Ag/AgCl (KCl sat.), and was characterized morphologically and electrochemically. Effect of loading level of nickel was examined by changing the number of potential cycles for the deposition of nickel nanoparticles, i.e., 1, 2 and 5 potential cycles were used. Also the effects of the electrooxidation of the thus deposited nickel nanoparticles and pH of the electrolyte on the voltammetric behavior were investigated. The good calibration curve of an acceptable rectilinear range is obtained at nano-NiO_x/Au electrode in which nano-Ni was prepared by two potential cycles and subsequently electro-oxidized in KOH solution.

A symmetrical tetradentate Schiff base ligand was derived by the condensation of the corresponding o-vanillin with urea. The synthesized Schiff base ligand was studied to characterize its ability as a cation carrier in poly(vinylchloride) membrane solid contact sensor. The constructed sensor showed excellent response characteristics to iron(III) ion. The electrode exhibited Nernstian slope of 19.5 mV/decade over a wide concentration range of iron(III) from 3.0 × 10^–6 to 1.3 × 10^–2 M with a detection limit of 1.2 × 10^–6 M. The sensor has fast response time, good reproducibility and excellent selectivity toward iron(III) ion with respect to many alkali, alkaline earth, transition and heavy metal ions. The potentiometric response of the sensor is independent of pH of the test solution in the range of 2.5–4.5. The applicability of the sensor was investigated by the determination of iron(III) concentration in pharmaceutical, biological and water samples.