Simultaneous Kinetic Spectrophotometric Determination of Hydrazine and Isoniazid Using H-Point Standard Addition Method and Partial Least Squares Regression in Micellar Media

The present study describes the application of simultaneous kinetic spectrophotometric determination of hydrazine (HZ) and isoniazid (INH), using H-point standard addition method (HPSAM) and partial least squares (PLS) calibration. The methods are based on the difference observed in the rate of iron (III) reduction with HZ and INH, in the presence of 2,2\u27-bipyridine (Bpy) and the subsequent complex formation between the resulted Fe2+ and Bpy in a solution containing sodium dodecyl sulfate (SDS) as a micellar medium. INH and HZ can simultaneously be determined between the range of 0.08−6.0 and 1.0−80.0 μg mL−1, respectively. The results have shown that by the application of HPSAM, the simultaneous determination could be performed with the ratio of 1:1000 to 1:12.5 for INH-HZ. Through the HPSAM analysis, the relative standard deviations of HZ and INH were 2.5 and 1.2, respectively. The total relative standard error for applying the PLS method to 9 synthetic samples, in the concentration ranges of 0.0−20.0 μg mL−1 of HZ and 0.5−3.0 μg mL−1 of INH, was 3.19. Both proposed methods (PLS and HPSAM) were successfully applied to the simultaneous determination of HZ and INH in several commercially available isoniazid formulations and satisfactory results were obtained.</p

Enhancement of photovoltaic performance using a novel photocathode based on poly(3,4-ethylenedioxythiophene)/Ag–CuO nanocomposite in dye-sensitized solar cells

A novel counter electrode (CE) based on a silver and copper oxide nanocomposite is developed and characterized by XRD and FE-SEM. A polymeric system containing poly(3,4-ethylenedioxythiophene) (PEDOT) is employed as the conductive polymer to prepare a transparent CE for a dye-sensitized solar cell (DSSC) device. Electrochemical analysis is used to study the catalytic activity of the reduction of triiodide ions in different DSSC-based CEs. To study the effect of photoelectrode modification on charge-transfer resistance, alternating current impedance spectroscopy is carried out. Power conversion efficiency and short-circuit current density ($J_{\mathrm{SC}}$) increase from 8.01% to 9.06% and 16.18 to 17.79 mA/cm2, respectively, due to the significantly improved electrical conductivity and electrocatalytic activity of the novel PEDOT/Ag–CuO nanocomposite-based CE

Enhancement of photovoltaic performance using a novel photocathode based on poly(3,4-ethylenedioxythiophene)/Ag–CuO nanocomposite in dye-sensitized solar cells

A novel counter electrode (CE) based on a silver and copper oxide nanocomposite is developed and characterized by XRD and FE-SEM. A polymeric system containing poly(3,4-ethylenedioxythiophene) (PEDOT) is employed as the conductive polymer to prepare a transparent CE for a dye-sensitized solar cell (DSSC) device. Electrochemical analysis is used to study the catalytic activity of the reduction of triiodide ions in different DSSC-based CEs. To study the effect of photoelectrode modification on charge-transfer resistance, alternating current impedance spectroscopy is carried out. Power conversion efficiency and short-circuit current density ($J_{\mathrm{SC}}$) increase from 8.01% to 9.06% and 16.18 to 17.79 mA/cm2, respectively, due to the significantly improved electrical conductivity and electrocatalytic activity of the novel PEDOT/Ag–CuO nanocomposite-based CE

Spectrophotometric determination of the acidity constants of calcon in water and mixed water–organic solvents

The acid–base properties of calcon (1-(2-hydroxy-1-naphthylazo)-2-naphthol-4-sulfonic acid) in water and mixed water–organic solvents at 25 °C at an ionic strength of 0.10 M are studied by a multiwavelength spectrophotometric method. The organic solvents used were the amphiprotic (methanol), dipolar aprotic (dimethylsulfoxide), and low basic aprotic (acetonitrile). To evaluate the pH absorbance data, a resolution method based on the combination of soft- and hard-modeling was applied. The acidity constants of all related equilibria were estimated using the whole spectral fitting of the collected data to an established factor analysis model. The data analysis program Datan was applied for determination of the acidity constants. The corresponding pKa values were determined in water and mixed water–organic solvents. Linear relationship between the acidity constants and the mole fraction of the different sol-vents in the mixtures exist. The effect of solvent properties on acid–base behavior is discussed

Preparation and electrochemical application of rutin biosensor for differential pulse voltammetric determination of NADH in the presence of acetaminophen

The electrocatalytic behavior of reduced nicotinamide adenine di-nucleotide (NADH) was studied at the surface of a rutin biosensor, using various electrochemical methods. According to the results, the rutin biosensor had a strongly electrocatalytic effect on the oxidation of NADH with the overpotential being decreased by about 450 mV as compared to the process at a bare glassy carbon electrode, GCE. This value is significantly greater than the value of 220 mV that was reported for rutin embedded in a lipid-cast film. The kinetic parameters of the electron transfer coefficient, a, and the heterogeneous charge transfer rate constant, kh, for the electrocatalytic oxidation of NADH at the rutin biosensor were estimated. Furthermore, the linear dynamic range; sensitivity and limit of detection for NADH were evaluated using the differential pulse voltammetry method. The advantages of this biosensor for the determination of NADH are excellent catalytic activity and reproducibility, good detection limit and high exchange current density. The rutin biosensor could separate the oxidation peak potentials of NADH and acetaminophen present in the same solution while at a bare GCE, the peak potentials were indistinguishable

Simultaneous Kinetic Spectrophotometric Determination of Hydrazine and Isoniazid Using H-Point Standard Addition Method and Partial Least Squares Regression in Micellar Media

The present study describes the application of simultaneous kinetic spectrophotometric determination of hydrazine (HZ) and isoniazid (INH), using H-point standard addition method (HPSAM) and partial least squares (PLS) calibration. The methods are based on the difference observed in the rate of iron (III) reduction with HZ and INH, in the presence of 2,2\u27-bipyridine (Bpy) and the subsequent complex formation between the resulted Fe2+ and Bpy in a solution containing sodium dodecyl sulfate (SDS) as a micellar medium. INH and HZ can simultaneously be determined between the range of 0.08−6.0 and 1.0−80.0 μg mL−1, respectively. The results have shown that by the application of HPSAM, the simultaneous determination could be performed with the ratio of 1:1000 to 1:12.5 for INH-HZ. Through the HPSAM analysis, the relative standard deviations of HZ and INH were 2.5 and 1.2, respectively. The total relative standard error for applying the PLS method to 9 synthetic samples, in the concentration ranges of 0.0−20.0 μg mL−1 of HZ and 0.5−3.0 μg mL−1 of INH, was 3.19. Both proposed methods (PLS and HPSAM) were successfully applied to the simultaneous determination of HZ and INH in several commercially available isoniazid formulations and satisfactory results were obtained.</p

Oxidized multi walled carbon nanotubes for improving the electrocatalytic activity of a benzofuran derivative modified electrode

In the present paper, the use of a novel carbon paste electrode modified by 7,8-dihydroxy-3,3,6-trimethyl-3,4-dihydrodibenzo[b,d]furan-1(2H)-one (DTD) and oxidized multi-walled carbon nanotubes (OCNTs) is described for determination of levodopa (LD), acetaminophen (AC) and tryptophan (Trp) by a simple and rapid method. At first, the electrochemical behavior of DTD is studied, then, the mediated oxidation of LD at the modified electrode is investigated. At the optimum pH of 7.4, the oxidation of LD occurs at a potential about 330 mV less positive than that of an unmodified carbon paste electrode. Based on differential pulse voltammetry (DPV), the oxidation current of LD exhibits a linear range between 1.0 and 2000.0 μM of LD with a detection limit (3σ) of 0.36 μM. DPV was also used for simultaneous determination of LD, AC and Trp at the modified electrode. Finally, the proposed electrochemical sensor was used for determinations of these substances in human serum sample

Electrochemical sensor based on multi-walled carbon nanotubes and 4-(((4-mercaptophenyl)imino)methyl) benzene-1,2-diol for simultaneous determination of epinephrine in the presence of acetaminophen

A carbon paste electrode modified with 4-(((4-mercaptophenyl)imino)methyl)benzene-1,2-diol (MIB) and multi-walled carbon nanotubes MIB /CNT/CPE) was prepared for determination of epinefrine (EP) in the presence of acetaminophen (AC). Cyclic voltammetry, chronoamperometry and differential pulse voltammetry (DPV) techniques were used to investigate the modified electrode for the electrocatalytic oxidation of (EP) and (AC) in aqueous solutions. The separation of the oxidation peak potential for EP- AC was 200 mV. Under the optimum conditions, the calibration curve for EP was obtained in the range of 1.0 to 25.0 µM and 25.0 to 500.0 µM. The diffusion coefficient for the oxidation of EP at the surface of modified electrode was calculated as 5.76×10-5 cm2s-1.</p

Improving the effective photovoltaic performance in dye-sensitized solar cells using an azobenzenecarboxylic acid-based system

In this research, an azobenzenecarboxylic acid was used as a sufficient co-adsorbent in combination with N719 dye. As it is found from the results, an optimized concentration of the co-absorbent leads to the highest efficiency. The dye-sensitized solar cells (DSSCs) parameters such as short-circuit current (Jsc), open-circuit voltage (Voc) and conversion efficiency (η) were obtained -14.87 mA/cm2, 0.765 V and 5.20% respectively. Based on the results, the N719/Azobenzenecarboxylic-based system shows a significant increase in Voc and Jsc, resulting in an ∼21% improvement in the efficiency. A higher conversion efficiency for the co-adsorbent-based systems was assigned to their enhanced η, which is attributed to reduced dye aggregation, higher electron injection and increased Voc. This corresponded to the improved electron density in the TiO2 conduction band of the photoanode and reduced charge recombination revealed through electrochemical impedance spectroscopy measurements. Also, evidence was provided for a long charge life time and a high resistance of charge recombination for the co-absorbed solar cells