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A new Al.sup.3+ carbon paste ion selective electrode based on N,N'-bis(salicylidene)-1,3-propanediamine (SB-Salpr) was prepared for the quantification of trace Aluminum. The proposed sensor has significant selectivity and sensitivity toward Al.sup.3+ ions in the presence of a wide range of cations including alkaline, alkaline earth, intermediate and heavy metal ions. The use of multi-walled carbon nanotubes (MWCNTs) and nanosilica in the composition of carbon paste sensors caused improvements in their characteristics; these materials have suitable conductivity and can help in conducting signals through the carbon paste sensors. The electrode consisted of 3% of MWCNTs, 0.5% of nanosilica, 25% of paraffin oil, 66.5% of graphite powder and 5% of SB-Salpr ligand. The sensor shows a Nernstian response to Al.sup.3+ ions with a Nernstian gradient of 20.2 ± 0.1 in the concentration range of 1.0 x 10.sup.-6 to 1.0 x 10.sup.-2 M with the detection limit of 2.1 x 10.sup.-7 M. The sensor response is independent of pH in the range of 24 and possesses the advantages of fast response time less than 5 s. According to the obtained results, Al.sup.3+ nanocomposite carbon paste sensor exhibited good selectivity in the presence of a few metal ions. The sensor was effectively used as an indicator electrode in the potentiometric titration of Al.sup.3+ ions with ethylenediaminetetraacetic acid., Author(s): Razieh Sanavi Khoshnood [sup.1], Setareh Akbari [sup.1], Toktam Mashayekhi Chenarbou [sup.2] Author Affiliations: (1) grid.411768.d, 0000 0004 1756 1744, Department of Chemistry, Mashhad Branch, Islamic Azad University, , Mashhad, [...]

Emission spectrometry with an argon arc source, ensuring the significant suppression of interferences with the molecular spectrum of CN, is used for the rapid direct determination of sulfur in pure graphite powders. A method of the time selection of the analytical signal of sulfur at the line 921.286 nm is proposed (signal registration within a certain interval of 9.8 s). The limit of detection for sulfur is 5 x 10.sup.-4 wt %. The analytical range is 5 x 10.sup.-4-2 x 10.sup.-2 wt % and can be expanded to 1 wt %. The time of a single analysis (3 replicate measurements) is 10 min. The work was performed on an MS-300 compact spectrometer, efficient in the range 908-930 nm, with an S13496 diode array photodetector., Author(s): D. O. Antonov [sup.1], E. G. Silkis [sup.2], B. K. Zuev [sup.1] Author Affiliations: (1) grid.439081.7, 0000 0004 0380 8849, Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy [...]

A new voltammetric approach was developed for the determination of paracetamol in tablet and syrup samples using chemometric optimization. The method is based on the use of the gold nanoparticles-polyaniline (AuNPs-PA) modified pencil graphite electrode (PGE). Electrode system was fabricated by using the electrochemical reduction of gold on aniline modified pencil electrode to give gold nanoparticles. A 3.sup.3 full factorial design was used to find optimal oxidation conditions of paracetamol on the AuNPs-PA-PGE. The optimal oxidation conditions of drug substance were found as -524 mV for the accumulation potential, 295 s for the accumulation time and pH 8.69 (for the phosphate buffer solution, 0.1 M). The determination of paracetamol was linear in the range of 2.0 x 10.sup.-7-6.0 x 10.sup.-6 M with a detection limit of 5 x 10.sup.-8 M. As a result, the proposed voltammetric approach gave satisfactory results for the determination of the related drug substance in tablets and syrup., Author(s): Remziye Güzel [sup.1], Haslet Eksi [sup.2], Erdal Dinç [sup.3], Ali Osman Solak [sup.4] Author Affiliations: (Aff1) 0000 0001 1456 5625, grid.411690.b, Dicle University, Faculty of Education, Department of Chemistry, [...]

A low-cost and simply fabricated amperometric glucose biosensor based on glucose oxidase (GOx) and 1,10-phenanthroline-5,6-dione (PD) modified graphite rod electrode was developed. The electrode exhibited good electrocatalytic activity with a well-defined hyperbolic dependence of amperometric signal upon glucose concentration in the presence and in the absence of oxygen. The electrode showed a good reproducibility and repeatability with relative standard deviation of less than 3 and 5%, respectively. The interaction of GOx with PD mediator was confirmed by means of UV-'Vis absorbance spectroscopy. Keywords: phenanthroline derivative, 1,10-phenanthroline-5,6-dione, glucose oxidase, glucose biosensor, amperometric sensors, electrocatalytic activity DOI: 10.1134/S1061934816010044, The development of biosensors is one of the most important directions in bioanalytical chemistry, because biosensors could be successfully applied for the determination of some toxic compounds [1] and biologically [...]

The potentials of using a graphite matrix for laser desorption/ionization from a thin-layer chromatography (TLC) spot is studied. Using a series of pharmaceutical substances with various functional groups and synthetic N-heterocyclic compounds, it was shown that the simple application of graphite onto TLC spots (outlining contour of the spots and shading the spots with a pencil lead) ensured the efficient desorption/ionization of analytes. In most of cases, the recorded mass spectra revealed only [[M + Na].sup.+] and [[M + K].sup.+] ion peaks, doublets of which can be used to determine molecular masses. The appearance of [[M + H].sup.+] ion peaks in some mass spectra may be due to the presence of mineral acids in the samples. The described approach to the application of the 'matrix' onto analyte spots eliminates the danger of spot blurring by a solution or an organic matrix, simplifies the procedure, and shortens the time of sample preparation. Keywords: graphite-assisted laser desorption/ionization, GALDI mass spectrometry, thin-layer chromatography, graphite, pharmaceutical substances, N-heterocyclic compounds DOI: 10.1134/S1061934814140032, INTRODUCTION Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) most often includes the use of various organic matrices. At the same time, the so called matrix-free versions, based on the activation of [...]

Cyclic and direct voltammetry with linear potential sweep has been used for the investigation of the dependence of the reversibility and reduction current in the system [Fe(CN).sup.3-.sub.6]/[Fe(CN).sup.4-.sub.6] on the concentrations of LiCl, NaCl, KCl, and CsCl solutions. The electrode was made of a graphite-epoxy composite and activated by mechanically cutting a surface layer directly in the solution and deactivated by the long-term storage in the air. The selected type of the graphite electrode and the method used to activate its surface provides the reversibility and diffusion control of the electrode process in the system [Fe(CN).sup.3-.sub.6]/ [Fe(CN).sup.4-.sub.6] regardless of the composition of the supporting solution. In the case of the deactivated electrode, the degree of irreversibility of this process depends on the form and concentration of metal chloride in the supporting electrolyte and the diffusion transfer is complicated by the adsorption of compounds formed between the ferricyanide and the cation of the supporting solution. Keywords: voltammetry, graphite electrode, ferricyanides DOI: 10.1134/S1061934811050091, One of the conditions of the successful development of chemistry, chemical technology, and methods of environment protection from pollution is the improvement of methods of analytical control. Among the great [...]