β-cyclodextrin and carboxymethylated β-cyclodextrin polymer film modified electrodes, hosting cobalt porphyrins, as sensors for electrocatalytic determination of oxygen dissolved in solution

Sensitive Detection of Levocetirizine as a new Generation Antihistamine by Stripping Square Wave Voltammetry

Background::

new and selective electrochemical sensor was developed for the determination of levocetirizine dihydrochloride, which is an antihistaminic drug.

Method::

The investigation was performed by using cyclic, differential pulse and square wave voltammetric methods on the β-cyclodextrin modified glassy carbon electrode. It is thereby planned to obtain information about levocetirizine determination and its mechanism.

Result::

The efficiency of experimental parameters including pH, scan rate, and accumulation potential and time on the anodic response of levocetirizine dihydrochloride was studied. By employing the developed method and under optimized conditions, the current showed linear dependence with a concentration in the range between 2 × 10-8 M and 6 × 10-6 M in pH 2.0 Britton Robinson (BR) buffer.

Conclusion::

The achieved limits of detection and quantification were found as 3.73 × 10-10 M and 1.24 × 10-9 M, respectively. In addition, the possibility of applying the developed sensor for real sample analysis was investigated, so β-cyclodextrin modified glassy carbon electrode was used to determine levocetirizine dihydrochloride in Xyzal® tablet dosage form. Finally, this sensor was successfully applied to the real sample as a selective, simple, reproducible, repeatable electrochemical sensor.

Cobalt porphyrins immobilized on niobium(V) oxide grafted on a silica gel surface: study of the catalytic reduction of dissolved dioxygen

Hematoporphyrin IX, H 2 HMP , 8,13-bis(1-hydroxyethyl)-3,7,12,17-tetramethyl-21 H ,23 H -porphine-2,18-dipropionic acid and protoporphyrin IX, H 2 PP , 8,13-divinyl-3,7,12,17-tetramethyl-21 H ,23 H -porphine-2,18-dipropionic acid were efficiently immobilized on niobium oxide grafted on a silica gel surface, SiO 2/ Nb 2 O 5, by the - COO – Nb bond formed between the porphyrin carboxyl groups and the grafted Nb 2 O 5. These immobilized porphyrins, SiO 2/ Nb 2 O 5/ H 2 HMP and SiO 2/ Nb 2 O 5/ H 2 PP , were further reacted with Co (II) in dimethylformamide, resulting in SiO 2/ Nb 2 O 5/ CoHMP and SiO 2/ Nb 2 O 5/ CoPP metallated complexes. The UV-vis spectra of the solid materials showed changes of the Q-bands ( a 2 u → e g transition) upon metallation, indicating that by incorporation of Co (II) in the porphyrin ring the local symmetry changed from D2 h to D4 h . These materials, when incorporated in carbon paste electrodes, presented the property of electrocatalyzing O 2 reduction. Rotating disk experiments were performed in order to estimate the number of electrons involved in the process. It was observed that, for both modified electrodes, O 2 was reduced to water in a four-electron process. Amperometric studies showed the potentiality of both modified electrodes as sensors for the determination of dissolved dioxygen. The response time was less than 3 s. A linear response for both systems was obtained between 2 and 12 ppm.

Electrochemical properties and dissolved oxygen reduction study on an iron(III)-tetra(o-ureaphenyl)porphyrinosilica matrix surface

Electrochemical reduction of dioxygen on an iron(III)-tetra-o-ureaphenylporphyrino-silica matrix surface ((o)- FeTUPPS ) obtained by attachment of the iron porphyrin tetraurea to a silica matrix through the sol-gel process was studied. Cyclic voltammetry and chronoamperometry techniques using as working electrode a carbon paste electrode modified with (o)- FeTUPPS , showed that (o)- FeTUPPS catalyzed O 2 reduction at −0.34 V vs SCE in 0.5 mol.L−1 KCl solution at pH 6. The electrode showed a linear and reproducible response to O 2 concentrations in the range ca. 0.5 and 11 mg.L−1 and was chemically stable under various oxidation-reduction cycles. From rotating disk experiments it was concluded that dissolved O 2 was reduced at the electrode surface to H 2 O 2 in a two-electron process.

Analytical Application of Oligopyrrole Macrocycles

Progress of modern analytical chemistry is closely related with advancement in other fields such as organic chemistry and biochemistry. Successful solution of current scientific problems is inconceivable without close cooperation of different chemical disciplines. As an example of such hot and very intricate theme research in the field of molecular recognition of biologically active compounds can serve, where numerous methods of analytical chemistry, organic chemistry and biochemistry can suitably be utilized, elaborated and brought into consonance. This multidisciplinary overlap logically leads to the advent of new scientific fields with their own tools, methodologies and subjects of exploration - bioanalytical chemistry and nanotechnology. This review covers different aspects of analytical application of oligopyrrole macrocycles (mainly porphyrins and sapphyrins). These compounds are widely used in analytical chemistry due to their outstanding optical properties. In our contribution oligopyrrole macrocycles are considered as signaling and structural parts of chemical receptors and selectors in various applications. Introduction of different moieties into meso-position of macrocyclic rings allows to obtain e.g., sterically well-organized receptors for recognition of biologically important analytes, new chromatographic materials, and powerful tools in electrochemical research. Finally, future trends in the field are outlined briefly.

Electrochemical Properties of a Porphyrin-Cobalt (II) Adsorbed on Silica-Titania-Phosphate Composite Surface Prepared by the Sol-Gel Method

SiO(2)/TiO(2)/phosphate was obtained by the sol-gel processing method, having the following characteristics: specific surface area S(BET)=800 m(2) g(-1), Ti=14.8 wt% and P=1.5 wt%, and ion exchange capacity of 0.58 mmol g(-1). The tetrakis(1-methyl-4-pyridyl) porphyrin ion, H(2)TmPyP(4+), was immobilized on the matrix surface by an ion exchange reaction and then metallated in situ with Co(II), resulting in SiO(2)/TiO(2)/phosphate/CoTmPyP material. The amount of CoTmPyP incorporated to the matrix was 35.0 µmol g(-1). Cyclic voltammetry studies and rotating disk electrode experiments using a carbon paste electrode made with the material were carried out. The immobilized complex catalyzed O(2) reduction to H(2)O at -0.22 V in 1 mol L(-1) KCl solution at pH 6.8. The cathodic current intensities plotted against O(2) concentrations, between 1 and 11 ppm, showed a linear correlation. Copyright 2000 Academic Press.