A simple and reliable voltammetric method is presented for the determination of amitriptyline using a boron-doped diamond electrode in 0.1 mol L-1 sulfuric acid solution as the support electrolyte. Under optimized differential pulse voltammetry conditions (modulation time 5 ms, scan rate 70 mV s-1, and pulse amplitude 120 mV), the electrode provides linear responses to amitriptyline in the concentration range 1.05 to 92.60 µmol L-1 and at a detection limit of 0.52 µmol L-1. The proposed method was successfully applied in pharmaceutical formulations, with results similar to those obtained using UV-vis spectrophotometric method as reference (at 95% confidence level), as recommended by the Brazilian Pharmacopoeia.

In this manuscript, a BiVO4 semiconductor was synthesized by solution combustion synthesis using different fuels (Alanine, Glycine and Urea). Also, the Tween® 80 surfactant was added during synthesis. BiVO4 was characterized by XRD, SEM and diffuse reflectance spectroscopy. Photocatalytic activity was evaluated by the discoloration of methylene blue at 664 nm under UV-visible light irradiation. According to XRD, the monoclinic phase of BiVO4 was obtained for the samples. The smallest particle size and highest k obs value were observed for the BiVO4/alanine sample, which promoted greater demethylation of methylene blue.

A simple procedure is described for the determination of scopolamine by square-wave voltammetry using a cathodically pretreated boron-doped diamond electrode. Cyclic voltammetry studies indicate that the oxidation of scopolamine is irreversible at a peak potential of 1.59 V (vs. Ag/AgCl (3.0 mol L-1 KCl)) in a 0.50 mol L-1 sulfuric acid solution. Under optimized conditions, the analytical curve obtained was linear (r = 0.9996) for the scopolamine concentration range of 1.0 to 110 µmol L-1, with a detection limit of 0.84 µmol L-1. The method was successfully applied to the determination of scopolamine in pharmaceutical formulations with minimum sample preparation.

Um procedimento simples é descrito para a determinação de propiltiouracil (PTU) por voltametria de pulso diferencial (DPV) usando um eletrodo de diamante dopado com boro (BDD) pré-tratado catodicamente. Estudos por voltametria cíclica indicam que a oxidação do PTU é irreversível a um potencial de pico de 1,42 V (vs. Ag/AgCl (KCl 3,0 mol L-1)) em uma solução tampão de Britton-Robinson (BR) (pH 2,0). Sob condições otimizadas, a curva analítica obtida foi linear (r = 0,9985) na faixa de concentração de PTU de 1,0 a 29,1 mmol L-1 em solução tampão BR (pH 2,0), com um limite de detecção de 0,90 mmol L-1. O método proposto foi aplicado com sucesso na determinação de PTU em amostras farmacêuticas, com resultados concordantes (a um nível de 95% de confiança) com aqueles obtidos empregando um método titulométrico oficial.

A simple procedure is described for the determination of propylthiouracil (PTU) by differential pulse voltammetry (DPV) using a cathodically pretreated boron-doped diamond (BDD) electrode. Cyclic voltammetry studies indicate that the oxidation of PTU is irreversible at a peak potential of 1.42 V (vs. Ag/AgCl (3.0 mol L-1 KCl)) in a Britton-Robinson (BR) buffer solution (pH 2.0). Under optimized conditions, the obtained analytical curve was linear (r = 0.9985) for the PTU concentration range of 1.0 to 29.1 mmol L-1 in a BR buffer solution (pH 2.0), with a detection limit of 0.90 mmol L-1. The proposed method was successfully applied in the determination of PTU in pharmaceutical samples, with results in agreement at a 95% confidence level with those obtained using an official titration method.

Neste trabalho descreve-se a titulação condutométrica do cloridrato de propranolol em formulações farmacêuticas usando nitrato de prata como titulante. O método é baseado na formação de um sal insolúvel (AgCl(s)) entre o cloreto da molécula do cloridrato de propranolol e os íons Ag(I) do titulante AgNO3. O efeito das concentrações PROP-AgNO3 e o intervalo de tempo entre adições sucessivas de titulante no formato da curva de titulação foram estudados. Recuperações para quatro amostras variaram de 96,8 a 105%. O método proposto foi aplicado na determinação do cloridrato de propranolol em diversas formulações farmacêuticas, com resultados concordantes com àqueles obtidos empregando-se o método oficial espectrofotométrico, a um nível de confiança de 95 %.

In this paper the conductometric titration of propranolol hydrochloride in pharmaceutical formulations using silver nitrate as titrant is proposed. The method was based on the formation of an insoluble salt (AgCl(s)) between the chloride of propranolol hydrochloride molecule and Ag(I) ions of the titrant AgNO3. The effect of the PROP-AgNO3 concentrations and the interval of time between the successive additions of the titrant on the shape of the titration curve were studied. The obtained recoveries for four samples ranged from 96.8 to 105%. The proposed method was successfully applied in the determination of propranolol hydrochloride in several pharmaceutical formulations, with results in close agreement at a 95 % confidence level with those obtained using official spectrophotometric method.

A simple, accurate and precise flow-injection turbidimetric procedure for the determination of fluoxetine hydrochloride in pharmaceutical formulations is reported. The procedure is based on the precipitation of chloride of fluoxetine hydrochloride with silver nitrate solution and the yielded insoluble AgCl(s) was monitored at 420 nm. The analytical curve was linear in the fluoxetine hydrochloride concentration range 3.0 x 10-5 - 5.0 x 10-4 mol L-1 with a detection limit of 10 µmol L-1 and, a sample throughout of 60 h-1.

A simple, precise, rapid and low-cost conductometric titration method for the determination of metformin hydrochloride (MET) in pharmaceuticals using silver nitrate as titrant is proposed. The method was based on the chemical reaction between the chloride of metformin hydrochloride molecule and Ag(I) ions, yielding the precipitate AgCl(s). The method was applied for MET determination in three pharmaceuticals and the obtained results with proposed method were in close agreement with those results obtained using an official method of the British Pharmacopoeia, at a 95% confidence level.