Cihan Topcu

PVC-Membrane Potentiometric Sensor for the Determination of Tamoxifen in Pharmaceutical Formulations

Novel tamoxifen-selective potentiometric electrodes based on various ion associations of tamoxifen were developed. The most suitable membrane composition, which has the best potentiometric characteristics, was examined under steady-state conditions. The membrane composed of (w/w) 3% tamoxifenphosphomolibdate ion pair, 32% poly(vinylchloride), and 65% 2-nitrophenyloctylether was determined as the membrane with the best analytical properties. On the condition of pH = 2-6, the fabricated electrode exhibited linear responses over the concentration range of 9.1 × 10-6 -1 × 10-3 M tamoxifen solutions (R2 = 0.9989) with a sensitivity of 42.9 ± 0.3 mV/decade, detection limit of 7.3 ± 0.4 × 10-6 M and short response time of ≈25 s. The influences of some alkaline, alkaline earth metals, biologically significant molecules, and some pharmaceutical species over electrode responses were studied. The proposed electrode was applied for the determination of tamoxifen contents of some pharmaceutical formulations by using standard addition method. The potentiometric analysis results obtained for the pharmaceutical formulations were in good harmony with the results obtained by high performance liquid chromatography at 95% confidence level.

Highly selective direct determination of chlorate ions by using a newly developed potentiometric electrode based on modified smectite

A novel polyvinyl chloride membrane chlorate (ClO3-) selective electrode based on modified smectite was developed for the direct determination of chlorate ions and the potentiometric performance characteristics of its were examined. The best selectivity and sensitivity for chlorate ions were obtained for the electrode membrane containing ionophore/polyvinylchloride/o-nitrophenyloctylether in composition of 12/28/60 (w/w%). The proposed electrode showed a Nernstian response toward chlorate ions at pH=7 in the concentration range of 1×10-7-1×10-1M and the limit of detection was calculated as 9×10-8M from the constructed response plot. The linear slope of the electrode was -61±1mVdecade-1 for chlorate activity in the mentioned linear working range. The selectivity coefficients were calculated according to both the matched potential method and the separate solution method. The calculated selectivity coefficients showed that the electrode performed excellent selectivity for chlorate ions. The potentiometric response of electrode toward chlorate ions was found to be highly reproducible. The electrode potential was stable between pH=4-10 and it had a dynamic response time of <5s. The potentiometric behavior of the electrode in partial non-aqueous medium was also investigated and the obtained results (up to 5% (v/v) alcohol) were satisfactory. The proposed electrode was used during 15 weeks without any significant change in its potential response. Additionally, the electrode was very useful in water analysis studies such as dam water, river water, tap water, and swimming pool water where the direct determination of chlorate ions was required.

Electrochemical Determination of Copper(II) in Water Samples Using a Novel Ion-Selective Electrode Based on a Graphite Oxide–Imprinted Polymer Composite

ABSTRACT A novel copper(II)-selective electrode based on graphite oxide/imprinted polymer composite was developed for the electrochemical monitoring of copper(II) (Cu2+) ions. The electrode exhibited highly selective potentiometric response to Cu2+ with respect to common alkaline, alkaline earth and heavy metal cations. The composite composition studies indicated that the most suitable composite composition performing the most promising potentiometric properties was 20.0% ionophore (Cu2+-ion imprinted polymer), 10.0% paraffin oil, 5.0% multiwalled carbon nanotubes, and 65.0% graphite oxide. The fabricated electrode exhibited a linear response to Cu2+ over the concentration range of 1.0 × 10− 6–1.0 × 10− 1 M (correlation coefficient of 0.9998) with a sensitivity of 26.1 ± 0.9 mV decade− 1. The detection limit of the fabricated electrode was determined to be 4.0 × 10− 7 M. The electrode worked well in the pH range of 4.0–8.0. The electrode had stable, reversible and fast potentiometric response (3 s). In addition, the electrode had a lifetime of more than 1 year. The analytical applications of the proposed electrode were performed using as an indicator electrode for the potentiometric titration of Cu2+ with ethylene diamine tetraacetic acid solution and for the determination of Cu2+ of spiked river, dam, and tap water samples. The obtained results for potentiometric titration and water samples were satisfactory.

Structural, thermal and morphological properties of a novel poly(acrylamide-co-methacrylic acid)/organoclay nanocomposite

ABSTRACT A novel poly(acrylamide-co-methacrylic acid)/organoclay nanocomposite was prepared and its structural, thermal, and morphological properties were investigated by various techniques. The absence of diffraction peaks for the organomodified-smectite nanocomposite showed that dispersion of the clay nanolayers within the polymer matrix was in the form of an exfoliated nanostructure. Morphological studies confirmed that organomodified-clay dispersed homogeneously in the polymer matrix. Infrared spectroscopy results indicated that the organosmectite is physically dispersed in the polymer network without forming any chemical bonds. The thermal analysis data revealed that there are significant increases in temperatures of decomposition and softening points of polymer with addition of organoclay.