Luiz Henrique Dall’Antonia

Surfactant effect on electrochemical-induced synthesis of α-Ni(OH)2

Nickel hydroxide films were electrosynthesized in the presence of different diluted surfactant solutions by galvanostatic electroprecipitation. Lamellar α-Ni(OH)2 films are obtained using cationic surfactant cetyltrimethylammonium bromide (CTAB), anionic surfactant sodium dodecyl sulfate (SDS), and also neutral surfactant Tween® 80. The films were structurally and morphologically characterized by X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy, and electrochemically by cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). The results evidenced that SDS remains intercalated between the lamellae of α-Ni(OH)2. Albeit the presence of CTAB and Tween® 80, it was noticed in FTIR spectra that the surfactants did not intercalate. The morphology was affected by the presence of different surfactants. All studied surfactants displaced the oxidation potential (EO) of Ni2+/Ni3+ process to less positive values. Also, the presence of surfactants improved the electrode charge efficiency and the charge response for the same number of moles of nickel ions deposited. The ratio of the charge and frequency change is 4.4 times bigger for films deposited with SDS when compared with pure α-Ni(OH)2 films.

A highly improved method for sensitive determination of amitriptyline in pharmaceutical formulations using an unmodified carbon nanotube electrode in the presence of sulfuric acid

The present paper describes a novel, simple and reliable differential pulse voltammetric method for determining amitriptyline (AMT) in pharmaceutical formulations. It has been described for many authors that this antidepressant is electrochemically inactive at carbon electrodes. However, the procedure proposed herein consisted in electrochemically oxidizing AMT at an unmodified carbon nanotube paste electrode in the presence of 0.1 mol L(-1) sulfuric acid used as electrolyte. At such concentration, the acid facilitated the AMT electroxidation through one-electron transfer at 1.33 V vs. Ag/AgCl, as observed by the augmentation of peak current. Concerning optimized conditions (modulation time 5 ms, scan rate 90 mV s(-1), and pulse amplitude 120 mV) a linear calibration curve was constructed in the range of 0.0-30.0 μmol L(-1), with a correlation coefficient of 0.9991 and a limit of detection of 1.61 μmol L(-1). The procedure was successfully validated for intra- and inter-day precision and accuracy. Moreover, its feasibility was assessed through analysis of commercial pharmaceutical formulations and it has been compared to the UV-vis spectrophotometric method used as standard analytical technique recommended by the Brazilian Pharmacopoeia.

Óxidos Mistos de Al2O3/ZrO2 como Inibidores de Corrosão do Aço SAE 1020

This paper describes the use of Al 2 O 3 /ZrO 2 mixed oxides synthesized by sol-gel process with different amounts of ZrO 2 (5%, 10%, 15% and 20% by mass) in the Al 2 O 3 matrix and different temperatures of calcination, such as interesting inhibitor materials of corrosive processes of SAE 1020 steel. The materials were characterized by Infrared Spectroscopy Fourier Transform (FTIR) and X-Ray Diffraction (XRD) techniques. FTIR spectra show the typical Al-O and Zr-O bonds vibrations in the mixed oxides. The XRD patterns of the samples calcined at 800 °C and 1000 °C shows the ZrO 2 tetragonal and γ-Al 2 O 3 face-centered cubic (FCC) phases. The corrosion tests showed that the SAE 1020 steel covered with mixed oxides have an anodic passive region, thereby inhibiting the corrosive processes on the metal surface. Furthermore, the found values for steel coated with mixed oxide synthesized indicate a decrease in corrosion potentials (E cor ) and corrosion current (i cor ). With respect to different samples of mixed oxides, the sample with 20 % of ZrO 2 in the Al 2 O 3 matrix proved to be the best inhibitor of steel corrosion, with the lowest values of corrosion potential and corrosion current, - 1.32 V and 0.31 μA cm -2 , respectively.