Rodrigo H. O. Montes

Fast determination of naproxen in pharmaceutical formulations by batch injection analysis with pulsed amperometric detection

A novel and fast electroanalytical method for naproxen determination in pharmaceutical formulations using batch injection analysis (BIA) with pulsed amperometric detection is described. Bare glassy carbon electrode was used as working electrode and 0.05 mol L-1 phosphate buffer solution as supporting electrolyte. The amperometric method involved the continuous application of two sequential potential pulses to the working electrode in order to detect naproxen by its electrochemical oxidation (+1.5 V for 200 ms) and to clean the electrode surface from adsorption products (+1.0 V for 100 ms), avoiding electrode contamination. The proposed method has several advantages for routine analysis, including: a low relative standard deviation between injections (3.0%, n = 10), high analytical frequency (90 h-1), satisfactory accuracy (based on comparative determinations by spectrofluorimetry) and low limit of detection (0.3 µmol L-1).

Flow-injection analysis with multiple-pulse amperometry for simultaneous determination of paracetamol and naproxen using a homemade flow cell for screen-printed electrodes

This work reports the simultaneous determination of paracetamol and naproxen using multiple-pulse amperometric detection on a multi-walled carbon nanotube modified screen-printed electrode (MWCNT-SPE) adapted in a homemade flow-injection analysis (FIA) cell. A sequence of two potential pulses (+0.30 and +0.70 V for 70 ms each) was applied continuously in such a way that paracetamol is selectively oxidized at +0.30 V and both compounds (paracetamol and naproxen) are oxidized at +0.70 V. Current subtraction after using a correction factor was employed for determination of naproxen without the interference of paracetamol. The proposed FIA method presents high selectivity and sensitivity, adequate accuracy (results in agreement with high-performance liquid chromatography), elevated analytical frequency (90 h-1), and low-cost once a single SPE strip can be used during the whole working day adapted in a flow-cell.

Determinação de peróxido de hidrogênio em antisséptico bucal usando um microdispositivo contendo partículas de azul da Prússia

A simple flow-injection amperometric procedure using a three-electrode-integrated sensor for the determination of H2O2 in antiseptic mouthwash is reported. This method involves the use of a working composite electrode modified with Prussian Blue (PB) particles that was easily adapted as detector in FIA. The best amperometric response was observed for a composite containing 30% of graphite modified with PB particles (GAP) and 70% of pure graphite (GR). The proposed method presents a linear response in the range of 10 to 200 μmol L-1. The detection and quantification limits were 0.8 and 2.6 μmol L-1, respectively.

Electrochemical Oxidation of Chlorhexidine and its Amperometric Determination by Flow-Injection Analysis

HClO 4 solution at a glassy-carbon electrode. The mechanism of the electrochemical oxidation of chlorhexidine is pH-dependent and involves a single-electron transfer possibly via radical cation formation. The FIA parameters were optimized and a detection limit of 0.3 µmol L -1 was obtained. The proposed method was applied in mouth rinses and skin disinfectants samples and compared with high-performance liquid chromatography.