This work presents a simple electrochemical method for 2-naphthylamine (2NAP) determination in perfume by differential-pulse voltammetry (DPV) employing a boron-doped diamond (BDD) electrode cathodically treated. Simple dilution of sample in supporting electrolyte was performed before electrochemical analysis. A borate buffer solution of pH 10.0 containing 20% (v/ (LOD) of 0.0046 µmol L-1 with a linear range between 0.5 and 90 µmol L-1, and RSD < 2.9%, respectively. Recovery values for spiked samples with 2NAP were between 102 and 104%. The proposed method is feasible to be applied for 2NAP detection and quantification on perfume samples with simple sample preparation.

In this paper, a simple, sensitive and precise electroanalytical method was developed using a chemically-reduced graphene-oxide (CRGO)-modified glassy carbon electrode and square wave voltammetry (SWV) for determination of ciprofloxacin in pharmaceutical formulations (tablets) and milk samples. Advantages of this sensor include a potential displacement of 100 mV and a 5-fold current increase for the electrochemical oxidation of ciprofloxacin, which resulted in a highly sensitive sensor, when compared to unmodified electrode. The improved properties of the modified electrode are likely due to the formation of a porous surface evidenced by the change in electrode kinetics (thin-layer diffusion process). The proposed sensor is free from interference of sample matrix (pharmaceutical formulations and low/high-fat milk) avoiding cumbersome processes such as previous separations, solvent extraction, or sample filtration (samples were only diluted in Britton-Robinson buffer solution). The results by SWV showed a limit of detection of 0.21 µmol L-1 (correspondent to 0.069 mg L-1), which is lower than the ones obtained using other carbon-based electrodes, relative standard deviations lower than 12%, and satisfactory recoveries in the range from 84 to 109%. The results obtained were statistically similar (95% confidence level) with those performed through high-performance liquid chromatography (HPLC).

This work demonstrates the application of batch-injection analysis (BIA) with amperometric detection on a multi-walled carbon nanotube (MWCNT) modified electrode for the sensitive determination of the antioxidant pyrogallol in biodiesel. Samples were diluted in electrolyte (0.1 mol L-1 HClO4) before injection using an electronic micropipette on the BIA cell. The size effect of MWCNTs on electrochemical oxidation of pyrogallol was investigated and 3.5-fold increase in the amperometric sensitivity using the modified electrode with MWCNTs of shorter dimensions was obtained. This result was in agreement with cyclic voltammetry and electrochemical impedance spectroscopy measurements. After optimization of BIA parameters for the amperometric detection on the MWCNT-modified electrode, the proposed method presented a linear range from 0.3 to 1000 µmol L-1, detection limit of 0.013 µmol L-1, precision of 3%, and sample throughput of 240 h-1. Spiked biodiesel samples were analyzed and recovery values between 95-99% were obtained.

A simple flow system with multiple pulse amperometric detection using a single working electrode is proposed for simultaneous determination of ascorbic (AA) and acetylsalicylic (AAS) acids in pharmaceutical formulations. The procedure is based on application of two potential pulses: 0.90 V/50 ms: oxidation and determination of AA without the interference of AAS; 1.35 V/50 ms: oxidation of both compounds and quantification of AAS by current subtraction using a correction factor. Sampling rate was estimated as 125 injections per hour and the limits of detection were 0.17 and 0.16 µmol L-1 for AA and AAS, respectively. Results for commercial samples agreed with those obtained using HPLC.

The present work describes the sorption potential of Dypterix alata (baru) for removal of Ni(II) in hydrous ethanol. Infrared spectroscopy was used for elucidating possible functional groups responsible for uptaking Ni(II). Sorption studies using Ni(II) standard solutions were carried out in batch experiments as functions of extraction time and pH solution. The Ni(II) was quantified before and after the removal experiments using Flame Atomic Absorption Spectrometry. Furthermore, based on adsorption studies and adsorption isotherms applied to the Langmuir and Freundlich models, it was possible to verify that D. alata presents a high adsorption capacity. The results show that D. alata can be used for removing Ni(II) in ethanol solutions.

Este trabalho descreve a utilização da análise por redissolução potenciométrica (PSA) sobre eletrodos de filme de mercúrio para a determinação de zinco em água de coco. Foi desenvolvida metodologia para o tratamento de tais amostras por ultra-som, otimizada para a determinação de zinco total por PSA. Um mililitro de amostra foi tratado com 2 mL da mistura 1:1 (v/v) de HCl concentrado e H2O2 (30% m/v) dentro de frascos fechados (4 mL) em um banho ultrassônico seguido de uma etapa de aquecimento em banho-maria por 15 min. Esta metodologia foi otimizada para a determinação de zinco total e foi validada através de análise direta das amostras por espectrometria de absorção atômica com forno de grafite (GFAAS). O limite de detecção obtido pelo método proposto por PSA foi de 1.35 µg L-1 (aplicando 45 s de pré-concentração). Tentativas para quantificar cobre nas mesmas amostras mostraram que o conteúdo deste metal é menor que o limite de detecção de ambas as técnicas, GFAAS e PSA (0.030 µg L-1 depois de 600 s de pré-concentração) com eletrodos de ouro.

This work describes the application of potentiometric stripping analysis (PSA) at mercury film electrodes for zinc determination in coconut water. A sample ultrasound-assisted treatment was developed and optimised for the total zinc determination by PSA. One milliliter of sample was treated with 2 mL of 1:1 (v/v) concentrated HCl and H2O2 (30% m/v) mixture in closed (4 mL) vessels under sonication (in ultrasonic bath), followed by a thermal step (in a boiling bath, for 15 min). This methodology was optimised for total zinc determination and was validated by graphite furnace atomic absorption spectrometry (GFAAS) analysis utilizing the sample without any treatment. The limit of detection obtained by the proposed PSA method was 1.35 µg L-1 (applying 45 s of preconcentration). Attempts to evaluate the amount of copper in the same sample show that the content of this metal is lower than the detection limits of both techniques, GFAAS and PSA (0.030 µg L-1 after 600 s of preconcentration) at gold film electrodes.

O controle do conteúdo de íons inorgânicos em combustíveis veiculares tem uma importante função na manutenção do motor. Um método novo e versátil para análise rápida de íons em etanol é apresentado. Eletroforese capilar foi utilizada para quantificar cátions (sódio, potássio, cálcio, magnésio e amônio) e ânions (sulfato, cloreto e nitrato). A injeção direta da amostra no capilar apresentou falta de repetibilidade nos resultados. A evaporação prévia do etanol, seguida pela resuspensão do material residual, levou a resultados confiáveis. Os limites de detecção para os oito íons estiveram na faixa de 0,06 a 0,18 mg L-1. Limites de detecção inferiores podem ser obtidos com o aumento do tempo de injeção e/ou da pressão de injeção.

The control of the content of inorganic ions in vehicular fuels plays an important role in the engine maintenance. A novel and versatile methodology to carry out rapid analysis of ions in ethanol is presented. Capillary electrophoresis was used to quantify cations (sodium, potassium, calcium, magnesium, and ammonium) and anions (sulfate, chloride, and nitrate). The injection of the sample directly in the capillary shows some lack of repeatability of the results. The prior evaporation of the ethanol, followed by a re-suspension of the residual material, leads to reliable results. The detection limits of the eight ions range between 0.06 and 0.18 mg L-1. Lower detection limits could be attained by increasing the injection time and/or the injection pressure.