High-efficiency ozone generation via electrochemical oxidation of water using Ti anode coated with Ni–Sb–SnO<Subscript>2</Subscript>

Ozone (O₃) has been generated on Ni–Sb–SnO₂/Ti electrode as anode immersed in acidic media at 25 °C by electrochemical process. The anode was electrochemically characterized by cyclic voltammetry and morphologically characterized by scanning electron microscopy (SEM) and X-ray diffraction. The concentration of dissolved ozone was determined by a UV/Vis spectrophotometer. The type of electrode with different times coating on the titanium mesh and different acid type and various concentrations (C _acid) were used, and the stability of the electrode was investigated under the experimental conditions by SEM images. Results shows that higher efficiency (53.7%) for O₃ generation by electrochemical oxidation of water were obtained in HClO₄ (1 M) and an applied potential of 2.4 V vs. Ag/AgCl in 150 ml volume undivided electrochemical cell.     

An investigation of phenolic compounds from plant sources as trypsin inhibitors

In the search of new trypsin inhibitors caffeic acid (1), cinnamic acid (2), gallic acid (3) and eugenol (4) from Cinnamomum zeylanicum, ferulic acid (5) from Impatiens bicolor, vanillin (6) from Melia azedarach and catechol (7) from Allium cepa were isolated through bioassay guided fractionation of the plant extracts. IC (50) values of the compounds 1, 2 and 5 were found to be 0.35?±?0.02?mM, 0.96?±?0.05?mM and 1.22?±?0.06?mM, respectively. Lineweaver-Burk and Dixon plots and their secondary replots showed that 1 was non-competitive inhibitor of this enzyme with K(i) value 0.102?±?0.006?mM.     

Ambidentate coordination of dimethyl sulfoxide in rhodium(III) complexes

The two dimethyl sulfoxide solvated rhodium(III) compounds, [Rh(dmso-κO)(5)(dmso-κS)](CF(3)SO(3))(3) (1 & 1* at 298 K and 100 K, respectively) and [Rh(dmso-κO)(3)(dmso-κS)(2)Cl](CF(3)SO(3))(2) (2), crystallize with orthorhombic unit cells in the space group Pna2(1) (No. 33), Z = 4. In the [Rh(dmso)(6)](3+) complex with slightly distorted octahedral coordination geometry, the Rh-O bond distance is significantly longer with O trans to S, 2.143(6) ? (1) and 2.100(6) ? (1*), than the mean Rh-O bond distance with O trans to O, 2.019 ? (1) and 2.043 ? (1*). In the [RhCl(dmso)(5)](3+) complex, the mean Rh-O bond distance with O trans to S, 2.083 ?, is slightly longer than that for O trans to Cl, 2.067(4) ?, which is consistent with the trans influence DMSO-κS > Cl > DMSO-κO of the opposite ligands. Raman and IR absorption spectra were recorded and analyzed and a complete assignment of the vibrational bands was achieved with support by force field calculations. An increase in the Rh-O stretching vibrational frequency corresponded to a decreasing trans-influence from the opposite ligand. The Rh-O force constants obtained were correlated with the Rh-O bond lengths, also including previously obtained values for other M(dmso)(6)(3+) complexes with trivalent metal ions. An almost linear correlation was obtained for the MO stretching force constants vs. the reciprocal square of the MO bond lengths. The results show that the metal ion-oxygen bonding of dimethyl sulfoxide ligands is electrostatically dominated in those complexes and that the stretching force constants provide a useful measure of the relative trans-influence of the opposite ligands in hexa-coordinated Rh(III)-complexes.     

Ultra Sensitive Quantification of Thiourea at Nanomolar Level by Catalytic‐Kinetic Differential Pulse Voltammetry

A new simple and highly selective and sensitive catalytic differential pulse voltammetry procedure for the determination of thiourea at nanomolar level is reported. Thiourea has a catalytic effect on the oxidation of Janus green by iodate in the hydrochloric acid medium. The potential was scanned in the negative direction and the differential pulse voltammograms were recorded. The variations of the peak current with hydrochloric acid concentration, oxidant, Janus green, pulse amplitude, pulse time and scan rate were optimized. Under the optimized conditions, the relationship between the peak current and concentration of thiourea was obtained. It is shown that the calibration curve is linear in the range of 0.01–6.00 µg/mL. The detection limit of the method was 0.005 µg/mL. The relative standard deviation for 6 replicate determinations of 0.01, 0.50 and 2.00 µg/mL is equal to 2.25%, 1.52% and 1.03%, respectively. The method was applied to the determination of thiourea in fruit juices with satisfactory results.     

Modified determination of dihydrostreptomycin in kidney, muscle and milk by HPLC.

A method is presented for the determination of dihydrostreptomycin in milk, muscle and kidney by reversed-phase ion-pair high-performance liquid chromatography and post-column derivatisation with beta-naphthoquinone-4-sulfonate prior to fluorescence detection. The new sample work-up procedures include acid precipitation of proteins and, in the case of muscle and kidney, removal of fats by solvent extraction followed by solid phase extraction on a cation exchanger. The fluorescence response was linear from 25 to 2000 micrograms l-1 of injected analyte. The detection limits were 10 micrograms kg-1 for milk and 15 micrograms kg-1 for muscle and kidney and the analyte recoveries were on average 93% for milk, 70% for kidney and 75% for muscle.     

One-pot efficient synthesis of disulfides from alkyl halides and alkyl tosylates using thiourea and elemental sulfur without contamination by higher polysulfides

An efficient and odorless synthesis of disulfides from alkyl halides using thiourea and elemental sulfur in the presence of sodium carbonate in wet polyethylene glycol (PEG 200) at 40 °C without contamination by higher polysulfides has been developed. This procedure was then extended to preparation of disulfides from alkyl tosylates at 70 °C.     

Three new cholinesterase-inhibiting cis-clerodane diterpenoids from Otostegia limbata

Three new tricyclic cis-clerodane type diterpenoids trivially named as limbatolide A (1), limbatolide B (2) and limbatolide C (3) have been isolated from the roots of Otostegia limbata along with two known compounds; oleanic acid and beta-sitosterol. The structure elucidation of the new compounds was based primarily on two-dimensional (2D) NMR techniques. Compounds 1-3 displayed inhibitory potential in a concentration-dependent manner against acetylcholinesterase (AChE; EC 3.1.1.7) and butyrylcholinesterase (BChE; EC 3.1.1.8) enzymes, respectively.     

Ultrasensitive Simultaneous Quantification of Nanomolar Level of Cd and Zn by Cathodic Adsorptive Stripping Voltammetry in Some Real Samples

A novel, simple and sensitive adsorptive stripping voltammetry method was developed for simultaneous determination of Cd and Zn using N‐Nitrozo‐N‐phenylhydroxylamine (Cupferron) as a selective complexing agent. Cadmium and zinc metals gave peaks that were distinctly separated by 450–1200 mV, allowing their determination over a wide range of concentrations. The influence of pH and the nature of supporting electrolytes, concentration of ligand, preconcentration time and applied potential were investigated. The detection limits were 0.058 ng/mL for Zn and 0.092 ng/mL for Cd, and the RSD at a concentration level of 50 ppb, were 1.8–2.1 % for both zinc and cadmium, respectively. The method was applied to the determination of cadmium and zinc in blood, drug, food and water samples with the satisfactory results.     

Modeling and optimizing of sonochemical degradation of Basic Blue 41 via response surface methodology

The nanocatalyst-assisted sonodegradation of Basic Blue 41 (BB41) dye in aqueous medium was modeled and optimized using response surface method (RSM) based on Box-Behnken design. The studied variables included pH, initial dye concentration, H₂O₂ concentration and sonolysis time while each factor varied at three levels: Low level (−1), Medium level (0) and High level (+1). The ultrasound -assisted degradation was well described by developing quadratic model with correlation value squared (R²) of 0.9114. Factor effects along with interaction effects were evaluated. The graphical optimization step was conducted to achieve the best experimental condition in dye removal. pH, H₂O₂ concentration and initial dye concentration of the reaction were investigated. It was recognized that at lower pH values the dye removal rate decreased. However, dye removal rate increased (82.5%) by increasing the concentration of H₂O₂ and by lowering the initial dye concentration.      

High sensitive determination of trace amount of cobalt by catalytic adsorptive stripping voltammetry

A very sensitive and selective catalytic adsorptive cathodic stripping procedure for trace measurements of cobalt is presented. The method is based on adsorptive accumulation of cobalt-CCA (calcon carboxylic acid) complex onto a hanging mercury drop electrode followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by nitrite. The effect of various parameters such as pH, concentration of CCA, concentration of nitrite, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum condition for the analysis of cobalt, include pH 5.2 (Acetate buffer), 2.1 μM clacon carboxylic acid, 0.032 M sodium nitrite and an accumulation potential of 0.05 V (versus Ag/AgCl). Under these optimum conditions and for an accumulation time of 60 s, the measured peak current at −0.480 V is proportional to the concentration of cobalt over the entire concentration range tested 0.003–2.0 ng ml⁻¹ with a detection limit of 1 pg ml⁻¹ for an accumulation time of 60 s and 2.0–10.0 ng ml⁻¹ for an accumulation time of 40 s. The relative standard deviations for ten replicate measurement of 0.5 ng ml⁻¹ of cobalt were 3.1%. The main advantage of this new system is the microtrace Co(II) determination by ASV. The method was applied to determination of cobalt in a water sample and some analytical grade salts with satisfactory results. Published in Elektrokhimiya in Russian, 2009, Vol. 45, No. 2, pp. 221–228. The article is published in the original.