Rodrigo Amorim Bezerra da Silva

Batch injection analysis with amperometric detection: application for simultaneous analysis using a single working electrode

In this work, we describe for the first time the association of batch injection analysis (BIA) with dual pulse amperometric (DPA) detection for simultaneous determination of multi-analytes using a single working electrode. The sequence of pulses is selected in such a way that the analytes are detected individually and independently at the same working unmodified electrode (using a correction factor). BIA provides fast response (high-throughput analysis), elevated precision, reduction of sample volumes and minimization of waste. To illustrate the potential of this method, BIA-DPA was applied for the simultaneous determination of biodiesel preservatives (tert-butylhydroquinone and butylated hydroxyanisole) and pharmaceutical compounds (paracetamol and caffeine or dipyrone and caffeine).

Reproductive biology of Hyla goiana (Anura, Hylidae)

Male-male and male-female interactions, reproductive habitat, and vocalizations of Hyla goiana B. Lutz, 1968 a member of H. polytaenia species group, are described. Three groups of calling males were surveyed along a small stream, at the Estacao de Pesquisa e Desenvolvimento Ambiental de Galheiro, Perdizes municipality, State of Minas Gerais, Brazil. The mean distance between the nearest calling neighbors was 2.7 m, in accordance with an uniform distribution. Clutches (mean 180 eggs) were deposited in the stream, submerged and attached to plants. In two observed courtships the female moved towards a calling male that rapidly clasped her. In the male-male interaction, the males emitted advertisement and encounter calls and then engaged in physical combat. The males have a prepollical fang-like spine on each hand and several of them were observed with scratches on dorsum. The advertisement call consists of alternating harsh notes and a trilled of brief notes. The frequency of the call is lower than that of H. aff. polytaenia and H. cipoensis B. Lutz, 1968. The clutch characteristics of H. goiana are similar to those described for H. polytaenia Cope, 1870 and H. cipoensis.

Three electrode electrochemical microfluidic cell: construction and characterization

This work describes the construction and characterization of an electrochemical flow-through microcell with the three electrodes (working, pseudo-reference, and auxiliary) inserted in microchannels with thickness smaller than 20 µm. These microchannels were constructed between two stacked polycarbonate slides using one or more overlapped toner masks as spacer. This strategy allows the construction of microcells with a variable internal volume on the working electrode (0.6 to 2.4 µL). Three different materials were optimized as electrodes: gold film or graphite-epoxy composite as working electrode, silver-epoxy composite as pseudo-reference electrode and, graphite-epoxy composite as auxiliary electrode. The performance of the microfluidic cell was characterized by cyclic voltammetry, potentiometric stripping analysis at constant current, and square wave anodic stripping voltammetry using ferrocyanide and heavy metals (Cu2+, Hg2+, Pb2+, and Cd2+) as model analytes.

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.

Desenvolvimento, caracterização e aplicação eletroanalítica de um compósito fluido de adesivo epóxi, grafite e ciclo-hexanona

A fluid conducting composite material prepared from graphite powder, commercial epoxy resin Araldite®, and cyclohexanone has been developed. The composition was optimized considering the mechanical properties as conductivity and adhesiveness using response surface methodology. This work employed cyclic voltammetry and amperometry to investigate the characteristics of such composite electrodes without and with the insertion of Prussian blue in the electrode body (bulk modified electrode). The composite electrodes were also successfully used for the amperometric detection of hydrogen peroxide at 0.0V vs Ag/AgCl.

3D printing for electroanalysis: From multiuse electrochemical cells to sensors

This work presents potential applications of low-cost fused deposition modeling 3D-printers to fabricate multiuse 3D-printed electrochemical cells for flow or batch measurements as well as the 3D-printing of electrochemical sensing platforms. Electrochemical cells and sensors were printed with acrylonitrile butadiene styrene (ABS) and conductive graphene-doped polylactic acid (G-PLA) filaments, respectively. The overall printing operation time and estimated cost per cell were 6 h and

Forrageamento de apis mellifera l. em oiticica (licania rigida)

6.00, respectively, while the sensors were printed within minutes (16 sensor strips of 1 × 2 cm in 10 min at a cost of

Rapid and selective determination of hydrogen peroxide residues in milk by batch injection analysis with amperometric detection

1.00 each sensor). The cell performance is demonstrated for the amperometric detection of tert-butylhydroquinone, dipyrone, dopamine and diclofenac by flow-injection analysis (FIA) and batch-injection analysis (BIA) using different working electrodes, including the proposed 3D-printed sensor, which presented comparable electroanalytical performance with other carbon-based electrodes (LOD of 0.1 μmol L-1 for dopamine). Raman spectroscopy and scanning electron microscopy of the 3D-printed sensor indicated the presence of graphene nanoribbons within the polymeric matrix. Electrochemical impedance spectroscopy and heterogeneous electron transfer constants (k0) for the redox probe Ru(NH3)6+3 revealed that a glassy-carbon electrode presented faster electron transfer rates than the 3D-printed sensor; however, the latter presented lower LOD values for dopamine and catechol probably due to oxygenated functional groups at the G-PLA surface.

Combination of screen-printed electrodes and batch injection analysis: A simple, robust, high-throughput, and portable electrochemical system

This research was carried at Campus IV do Centro de Ciencias Humanas e Agrarias da Universidade Estadual da Paraiba, Catole do Rocha, Paraiba, Brazil, to study the foraging behavior of Apis mellifera L. on Licania rigida flowers along day. The number of visits that bees made to flowers from 07:00 to 17:00 hours, were recorded every 10 minutes, during six days. The results showed that honey bees foraged for nectar more frequently under shaded and wind protected parts.