Electrochemical behavior study of salicylic acid following azo dye formation with 2,4-dinitrophenylhydrazine: Analytical evaluation

A new simple, accurate and cost-effective chronoamperometry (CA) - based approach coupled with azo coupling reaction has been put forward for quantitative analysis of salicylic acid. The reaction involves a two-step process of oxidation of the 2,4-dinitrophenylhydrazine (DNPH) by potassium iodate to give a 2,4-dinitrophenylhydrazinium cation at 0–5 °C and coupling with salicylic acid (SA) to form red salicylic acid-derived azo dye. Electrochemical impedance spectroscopy, square wave voltammetry and chronoamperometry methods were used to characterize the electrochemical behavior of the salicylic acid-derived azo dye. Studies on different variables affecting the reaction were optimized. Under the optimal conditions, amperometric studies showed that the current response exhibits a wide linearity range from 0.1 to 0.0005 mmol L−1 for SA and the limit of detection and quantification are found to be 0.0001 and 0.0015 mmol L−1 (S/N = 3 & 10) respectively. Therefore, the developed method was successfully applied for routine determination of SA in pharmaceutical samples. Keywords: salicylic acid, Azo coupling, DNPH, Chronoamperometr

Electrochemical impedance spectroscopy measurements for determination of derivatized aldehydes in several matrices

A simple, selective and sensitive electrochemical method is described for the determination of different aldehydes at glassy carbon electrode using electrochemical impedance spectroscopy (EIS). The measurements were performed after their derivatization with 2,4-dinitrophenylhydrazine (DNPH) in acidic medium. The impedance measurements were investigated in the frequency range from 100 mHz to 100 kHz at a potential of 1.0 V versus Ag/AgCl. The Nyquist plots were modeled with a Randle’s equivalent circuit. The charge transfer resistance was identified as the dependent parameter on relevant concentration of aldehydes (determined as their hydrazones). Under the optimized conditions, the linearity was established over the concentration range of 1000–0.05 μmol L−1. The limits of detection (LODs) obtained were from 0.097 to 0.0109 μmol L−1. Finally, the developed method has been applied to the determination of aldehydes in drinking water, orange juice and apple vinegar samples with relative standard deviations (RSDs) < 3.1% and acceptable recovery rate (around of 80%)

Synthesis, characterization and efficient photocatalytic properties of spinel materials for dye degradation

In this research, Co0.5Zn0.5Al2O4 spinel oxides photocatalysts were elaborated from layered double hydroxides Co-Zn-Al/CO3 precursor by calcination at 300, 400, 500, 600, 800, and 1000 °C. XRD, FTIR, TGA/DTA, and SEM/EDX analysis were used for characterized of prepared photocatalysts. The photocatalytic efficiency of the prepared materials was tested by photodegradation of methyl orange (MO) azo dye as a model of textile contaminants under UV illumination. The effect of various operational factors such as irradiation time, initial pH, catalyst dose, methyl orange concentration and reuse were investigated. The enhancement of the photodegradation was strongly dependent on the calcination temperature. A synergic effect between the adsorption and photodegradation was observed. After 50 min of irradiation, the catalyst calcined at 400 °C showed the highest efficiency (98.2%). After regeneration (up to five cycles), the photocatalyst showed high stability

Experimental and density functional theory studies of methyl orange adsorption on Ni-Al/LDH intercalated sodium dodecyl sulfate

This study examined the application of Ni-Al layered double hydroxide (Ni-Al/LDH) intercalated with sodium dodecyl sulfate (SDS) anion as an adsorbent for the elimination of methyl orange (MO) model dye from aqueous solutions. Material has been synthesized using a co-precipitation process with a molar ratio of Ni/Al of 3. XRD, FTIR, TEM/EDX and TGA/DTA were used to determine structural, morphological and thermal properties of the material. Under varied circumstances, the adsorption capability for MO dye elimination was tested in batch mode. The experimental findings demonstrate that the greatest adsorption takes place at pH levels ranging from neutral to acidic. Kinetic data were well-suited to the pseudo-second-order model. Equilibrium isotherm adsorption data were correlated to the Langmuir model with a high adsorption capacity of 808.8 mg/g. The adsorption process was exothermic and spontaneous nature. In order to analyze the adsorbate-adsorbent interaction mechanism, the anionic dye MO structure was evaluated using the Gaussian 09 W program at the B3LYP/LANL2DZ level. The quantum descriptors examined supported the experimental results obtained in this study

Effect of natural phosphate to remove silver interference in the detection of mercury(II) in aquatic algae and seawater samples

AbstractA silver particles impregnated onto natural phosphate (Ag/NP) was synthesized using reaction in solid state. The obtained powder was characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The (Ag/NP) was used as modifier of carbon paste electrode (CPE) to determine mercury by square wave voltammetry. The calibration graph obtained is linear from 1.0×10−8mol·L−1 to 1.0×10−5mol·L−1 at preconcentration time of 5min, percentage loading of 7%, with correlation coefficient of 0.993. The limits of detection (DL,3σ) and quantification (QL,10σ) were 5.8×10−9mol·L−1 and 19.56×10−9mol·L−1 respectively. The repeatability of the method expressed as relative standard deviation (R.S.D.) is 2.1% (n=8). The proposed method was successfully applied to determine mercury(II) in aquatic algae and seawater samples