Andressa Galli

Utilização de técnicas eletroanalíticas na determinação de pesticidas em alimentos

The aim of this work is to discuss selected applications of electroanalytical techniques for the detection of pesticides in foods and beverages, published in the last ten years. The applications involved different working electrodes for the electroanalytical determination of pesticides, namely amperometric biosensors, cholinesterase-based biosensors, polymer-modified electrodes, ultramicroelectrodes and hanging mercury drop electrodes. They were used for several voltammetric and amperometric techniques in different analytical procedures for the detection and quantification of different classes of pesticides in different food matrices.

UTILIZAÇÃO DA MÚLTIPLA VOLTAMETRIA DE ONDA QUADRADA NA DETERMINAÇÃO ELETROANALÍTICA DE COMPOSTOS ORGÂNICOS E INORGÂNICOS

This paper reports the development of multiple square wave voltammetry and the possibilities of its use for electroanalytical determinations of organic and inorganic compounds with the improvement of the signal-to-noise ratios and detection limits 2-3 orders of magnitude lower than those obtained with conventional square wave voltammetry. The theoretical aspects and analytical applications were demonstrated as an increased analytical response (current) and application of different pulse modes for different redox processes. Preliminary results obtained for several redox systems using different electrode surfaces are shown, demonstrating also that MSWV represents an excellent alternative for the determination of ultra-traces of organic and inorganic compounds.

VALIDAÇÃO INTRALABORATORIAL DA DETERMINAÇÃO DE METILTESTOSTERONA EM ÁGUAS NATURAIS POR VOLTAMETRIA USANDO ELETRODO DE GOTA PENDENTE DE MERCÚRIO

17α-methyltestosterone (17α-MT) is a hormone used in medicine and aquaculture which can be found in natural waters. It is considered an emerging organic pollutant and its accurate and precise analysis is required. Therefore, this study presents the in-house validation of a new voltammetric methodology for 17α-MT analysis in natural waters. A hanging mercury drop electrode and NaOH 5.0×10-3 mol L-1 solution as the electrolyte were employed in the voltammetric determinations. To confirm the presence of 17α-MT in water samples quantitative analysis was performed by ESI-MS/MS. The methodology exhibited good selectivity, linearity, accuracy (recovery of between 100.4 and 108.8%) and precision (RSDs for repeatability of 2.85% and for intermediate precision of 14.10%, with n = 5, respectively). LOD and LOQ were 3.07 µg L-1 and 10.78 µg L-1, respectively. The methodology was suitable for determination of 17α-MT in natural waters due to low-cost, good performance and no sample pre-treatment required.

Development of an Electroanalytical Methodology for Determination of Pesticide Glyphosate in Environmental Samples

This paper describes the development of an electroanalytical methodology using square wave voltametry (SWV) and hanging mercury drop electrode (HMDE) for determining the pesticide glyphosate in samples of natural waters. The electroactivity of glyphosate on the mercury electrode was obtained by complexation with Cu(II) were evaluated in the study the voltammetric parameters and experimental involved in the electrochemical reduction, such as: concentration of Cu(II), an effect of supporting electrolytes at different pH values and parameters of SWV. The best results were obtained in solution of NaNO2 the 0,10 mol L , pH 6,5, concentration of Cu(II) of 2,61 x 10 mol L, pre-concentration time of 120 sec, using the frequency of application of pulses of potential of 100 sec, amplitude of pulses of potential of 50 mV and increase of sweep of 6 mV. The complex Cu(II)-glyphosate showed only a reduction peak at 0,1 V with quasi reversible process controlled by diffusion of the species on the electrode surface. Calibration curves were constructed and the detection limits (LD) and of quantification (LQ) obtained were (22,04 ± 0,42) μg L and (73,46 ± 1,41) μg L, respectively. The recovery tests showed values of (100,27 ± 1,96) % in pure water laboratory and (99,12 ± 2,14) % in real sample. Additionally, the methodology was applied for determination of glyfhosate in water sample collected in the creek from the Santa Clara, in the municipality of Candói/PR, with a value of (311,02 ± 23,72) μg L glyphosate present in the sample. The percentage recovery in the investigated samples were above 99%, thus the gliphosate can be quantified in water samples by the proposed method.

Interferentes Endócrinos em Águas Naturais: Determinação Voltamétrica de 17alfa-Metiltestosterona

Os hormonios sexuais incluindo o 17 a -metiltestosterona (MT) pertencem ao grupo de compostos considerados disruptores endocrinos. No entanto, poucos estudos reportam o hormonio MT em amostras ambientais. Nesse contexto, este trabalho descreve a determinacao direta de MT em amostras de aguas naturais baseado na electroreducao, empregando o eletrodo de gota pendente de mercurio e a voltametria de onda quadrada. DOI: 10.5935/1984-6835.20140029