Voltammetric determination of Basic Red 13 during its sonoelectrocatalytic degradation

Microchimica Acta - The article describes a sensor for the voltammetric determination of the azo dye Basic Red 13 (BR13) during its degradation by using sonoelectrochemistry in the presence of TiO2...     

A Unique Example of a Co-crystal of [Co(AMTTO)2(H2O)2](NO3)2 and [Co(AMTTO)2(CH3CN)2](NO3)2 (AMTTO = 4-amino-5-methyl-1,2,4-triazol-3(2H)-thione)

A co-crystal of cobalt(II) complexes, Co(AMTTO)₂(CH₃CN)₂]²⁺(NO₃)₂. [Co(AMTTO)₂(H₂O)₂]²⁺(NO₃)₂, compound (1) was isolated from the reaction of Co(NO₃)₂?6H₂O and 4-amino-3-mercapto-6-methyl-5-oxo-1,2,4-triazine (AMTTO) in acetonitrile as solvent. Isolated crystals were characterized by elemental analyses, IR spectroscopy as well as X-ray diffraction studies. Crystal data for 1 at 95 K revealed a monoclinic space group P2₁/n, a?=?11.7903(5), b?=?12.1279(5), c?=?14.1443(6) Å, β?=?99.244(4)°, Z?=?2, R₁?=?0.0339. Compound 1 consists of two co-crystallized Co(II) complexes [Co(AMTTO)₂(CH₃CN)₂]²⁺ and [Co(AMTTO)₂(H₂O)₂]²⁺ and four nitrate counter anions In both complexes, cobalt(II) ions are in an octahedral arrangement. Two S, N bidentate AMTTO ligands are coordinated to both Co(II) ions. The coordination sphere of Co1 is completed by two acetonitrile molecules, and these positions are occupied by water molecules for Co2.

Graphic Abstract

A co-crystal of cobalt(II) compound was isolated from the reaction of Co(NO₃)₂?6H₂O and 4-amino-3-mercapto-6-methyl-5-oxo-1,2,4-triazine in acetonitrile as solvent.

     

Kinetic determination of thiocyanate on the basis of its catalytic effect on the oxidation of methylene blue with potassium bromate.

This study reports a sensitive kinetic spectrophotometric method for the determination of trace amounts of thiocyanate. In acidic solution, Methylene Blue (MB) is oxidized by bromate to form a colorless compound. The reaction is accelerated by trace amounts of thiocyanate and can be followed by measuring the absorbance at 664 nm. The absorbance of the reaction decreased with an increase in the reaction time. Under the optimum experimental conditions (0.56 M of sulfuric acid, 3.9 x 10(-5) M of MB, 3.0 x 10(-3) M of bromate, 180 s, 25 degrees C), thiocyanate can be determined in the range 5.0 - 180 ng/ml. The relative standard deviations (n = 8) are 2.81 and 1.43% for 10.0 and 150 ng/ml thiocyanate, respectively. The detection limit of this method is (3sigma) 3.8 ng/ml. This method was successfully applied to the determination of thiocyanate in real samples.     

Developing a sensor for the simultaneous determination of adrenaline,uric acid,and tryptophan

A chemically modified electrode is constructed based on a coumestan derivative and multiwall carbon nanotubes modified carbon paste electrode (CMWCNT-CPE). The surface charge transfer rate constant, k _s, and the charge transfer coefficient, α, for the electron transfer between coumestan and MWCNT-CPE were estimated. CMWCNT-CPE presents a highly catalytic activity for adrenaline (AD) electrooxidation. The results show that the peak potential of AD at the CMWCNT-CPE surface shifted by about 145 mV toward negative values compared with that at the MWCNT-CPE surface. Differential pulse voltammetry exhibited three linear ranges and a detection limit of 0.2 μM for AD. For a mixture containing AD, uric acid (UA), and tryptophan (Trp), three signals corresponding to the analytes could well separate them from each other. Moreover, CMWCNT-CPE was used to determine AD in an adrenaline injection solution and UA in a human urine sample with satisfactory results. To confirm the proposed method, the AD injection solution and the urine sample were spiked with different certain amounts of AD, UA, and Trp.     

A comparison of the electrochemical and electroanalytical behavior of ascorbic acid,dopamine and uric acid at bare,activated and multi-wall carbon nanotubes modified glassy carbon electrodes

The electrochemical oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA), as three important biological molecules, have been studied at the bare, activated and multi-wall carbon nanotubes modified glassy carbon electrodes (MWCNTGCE) using different voltammetric methods. MWCNT-GCE not only exhibited both the roles of mediator and promoter for AA oxidation, but also performed the role of an excellent promoter for electrochemical oxidation of DA and UA when compared with bare GCE (BGCE) or activated GCE (AGCE). The results show that the oxidation of AA at MWCNT-GCE exhibits the characteristic shape typical of an EC catalytic (E_rC_i ^'anism. In differential pulse voltammetric measurements, MWCNTGCE and AGCE could separate the oxidation peak potentials of AA, DA and UA present in the same solution, though the MWCNT-GCE remarkably improves the sensitivity of determination of the analytes and also reduces the fouling effects as compared to AGCE. Furthermore, the hydrodynamic amperometry at rotating MWCNT-GCE at constant potential was used for determination of AA, DA and UA individually in the presence of the other two species. It has been shown that using MWCNTGCE, these three species can be determined by amperometry with high sensitivity and selectivity. Finally, MWCNT-GCE has been applied to simultaneous determination of AA and DA in the related injection solutions and UA in a human urine sample with satisfactory results.