In this work, a new and sensitive electroanalytical methodology was developed and validated to quantify sulfentrazone in soil samples. Sulfentrazone was initially characterized qualitatively using cyclic voltammetry (CV). Its oxidation occurred by diffusion (mass transport) on a glassy carbon electrode (GCE) via irreversible transfer of one electron close to a peak potential of +0.936 V vs. Ag|AgCl, 3.0 mol L-1 KCl, in 0.10 mol L-1 KOH. Differential-pulse voltammetry (DPV) was the most sensitive and selective technique, with limits of detection (LOD) of 1.94 and 2.19 mmol L-1 and limits of quantification (LOQ) of 6.46 and 7.31 mmol L-1, in the absence and presence of soil matrix, respectively. The reproducibility of the method ranged between 2.65 and 4.2%, with intermediate precision between 5.32 and 10.9%. The recovery rate ranged between 88.5 and 103%. Additionally, the accuracy of the electroanalytical method was validated by comparing the results with data from a standard analytical methodology of high-performance liquid chromatography (HPLC/UV-Vis).

Fall armyworm, Spodoptera frugiperda J.E. Smith, 1797 (Lepidoptera: Noctuidae) is the main pest of maize, besides attacking sorghum and cotton crops. The control of this pest has been accomplished mainly with the use of synthetic insecticides but, due to the growing concern about the environment and food quality, phenolic compounds have shown their potential for the biological control of this insect. Thus, the objective of the present study was to evaluate the efficiency of the extract of jabuticabeira, Myrciaria cauliflora [Mart.] O. Berg (Myrtaceae) fruit skin flour in the control of S. frugiperda. Skins of M. cauliflora Sabará genotype were dried at 45 °C in a forced air oven. In order to obtain the extract, 1.0 g flour was mixed with 10 mL acetone: water solution (7:3 v/v). Forty-eight-hour-old S. frugiperda caterpillars were placed in glass tubes with an artificial diet containing the extract at concentrations of 0, 250, 500, 1000, and 2000 mg L-1. The extract, in which the phenolic compounds gallic acid, gallocatechin, catechin, epicatechin, ellagic acid, and salicylic acid were identified at a concentration of 2000 mg L-1, in average, increased mortality rates by 150% in the larval stage, duration of larval stages by 60%, and pupal by 17%, and decreased amount of females by 55%. On the other hand, the extract at 1000 mg L-1 only increased duration of larval period by 24%. It was concluded that the extract is harmful to this insect, probably due to the presence of phenolic compounds.

O açúcar é amplamente consumido em todo o mundo e o Brasil é o maior produtor, consumidor e exportador deste produto. Para garantir o bom desenvolvimento e produtividade das culturas de cana de açúcar, é necessário aplicar grandes quantidades de agrotóxicos, principalmente herbicidas e pesticidas. O herbicida tebuthiuron (TBH) impede a pré e pós-emergência das plantas daninhas infestantes nas culturas de cana de açúcar. Considerando que é importante para garantir a segurança alimentar da população, este trabalho propõe um método confiável para analisar TBH em matrizes de açúcar (mascavo e cristal), usando voltametria de onda quadrada (SWV) e voltametria de pulso diferencial (DPV) em eletrodo de carbono vítreo e investigar o comportamento eletroquímico do herbicida por voltametria cíclica (CV). Os nossos resultados sugerem que TBH ou o produto da sua reação com o eletrólito de suporte é oxidado através da transferência irreversível de um elétron entre o analito e eletrodo de trabalho, a um potencial de cerca de +1,16 V vs. Ag|AgCl sat em 0,10 mol L-1 KOH como solução de eletrólito de suporte. Tanto DPV quanto SWV são satisfatórios para a análise quantitativa do analito. DPV é mais sensível e seletiva, com limites de detecção de 0,902, 0,815 e 0,578 mg kg-1, e limite de quantificação de 0,009, 0,010 e 0,008 mg kg-1, na ausência da matriz, e na presença de matriz de açúcar cristal e mascavo, respectivamente. Reprodutibilidade situou-se entre 0,53 e 13,8%, a precisão variou entre 4,14 e 15,0%, e a recuperação manteve-se entre 84,2 e 113% para DPV conduzido na ausência e na presença da matriz de açúcar cristal, respectivamente.

Sugar is widely consumed worldwide and Brazil is the largest producer, consumer, and exporter of this product. To guarantee proper development and productivity of sugar cane crops, it is necessary to apply large quantities of agrochemicals, especially herbicides and pesticides. The herbicide tebuthiuron (TBH) prevents pre- and post-emergence of infesting weed in sugarcane cultures. Considering that it is important to ensure food safety for the population, this paper proposes a reliable method to analyse TBH in sugar matrixes (brown and crystal) using square wave voltammetry (SWV) and differential pulse voltammetry (DPV) at bare glassy carbon electrode and investigate the electrochemical behavior of this herbicide by cyclic voltammetry (CV). Our results suggest that TBH or the product of its reaction with a supporting electrolyte is oxidized through irreversible transfer of one electron between the analyte and the working electrode, at a potential close to +1.16 V vs. Ag |AgCl sat in 0.10 mol L-1 KOH as supporting electrolyte solution. Both DPV and SWV are satisfactory for the quantitative analysis of the analyte. DPV is more sensitive and selective, with detection limits of 0.902, 0.815 and 0.578 mg kg-1, and quantification limits of 0.009, 0.010 and 0.008 mg kg-1 in the absence of the matrix and in the presence of crystal and brown sugar matrix, respectively. Repeatability lay between 0.53 and 13.8%, precision ranged between 4.14 and 15.0%, and recovery remained between 84.2 and 113% in the case of DPV conducted in the absence of matrix and in the presence of the crystal sugar matrix, respectively.

Um método eletroanalítico foi desenvolvido para determinação simultânea de íons cobre e chumbo em cachaça empregando eletrodo de pasta de carbono modificado com ácido ascórbico e nanotubos de carbono (CPE-AaCNT). A técnica de voltametria de onda quadrada (SWV) com redissolução anódica foi empregada e otimizada com relação aos seguintes parâmetros: frequência (50 Hz), amplitude (100 mV) e incremento de varredura (9 mV). As curvas analíticas apresentaram intervalo linear de 0,09 a 7,00 mg L- 1 para o chumbo e para o cobre. Os limites de detecção foram de 48,5 e 23,9 µg L- 1 para o chumbo e o cobre, respectivamente. O método desenvolvido foi aplicado na determinação simultânea de chumbo e cobre em cinco amostras comerciais de cachaça. Os resultados apresentaram-se concordantes com os obtidos por F AAS/GF AAS (espectrometria de absorção atômica com chama/espectrometria de absorção atômica com forno de grafite) e revelaram que CPE-AaCNT podem ser empregados com êxito na quantificação de cobre e chumbo em amostras comerciais de cachaça.

The development of an electroanalytical method for simultaneous determination of copper and lead ions in sugar cane spirit (cachaça) using carbon paste electrode modified with ascorbic acid and carbon nanotubes (CPE-AaCNT) is described. Squarewave voltammetry (SWV) with anodic stripping was employed, and this technique was optimized with respect to the following parameters: frequency (50 Hz), amplitude (100 mV) and scan increment (9 mV). The analytical curves were linear in the range from 0.0900 to 7.00 mg L- 1 for lead and copper. The limits of detection were 48.5 and 23.9 µg L- 1 for lead and copper, respectively. The developed method was applied to the simultaneous determination of copper and lead in five commercial samples of sugar cane spirit. The results were in good agreement with those obtained by F AAS/GF AAS (flame atomic absorption spectrometry/graphite furnace atomic absorption spectrometry) and showed that CPE-AaCNT can be successfully employed in the simultaneous determination of these metals in real sugar cane spirit samples.

A cachaça, tradicional e popular bebida brasileira, é obtida por meio da destilação do mosto fermentado de cana de açúcar. Dentre as etapas do processo de produção da bebida, o envelhecimento natural consiste em armazená-la em recipientes de madeira apropriados por um tempo determinado, onde ocorrem alterações na composição química, aroma, sabor e cor da bebida. Este trabalho teve como objetivo realizar um acompanhamento da composição fenólica em diferentes períodos de envelhecimento da cachaça em tonel de carvalho (Quercus sp.). Foram realizadas coletas periódicas durante o período de envelhecimento da cachaça em tonel de carvalho e realizaram-se análise de treze compostos fenólicos utilizando a técnica de cromatografia líquida de alta eficiência com detector de arranjo de diodos (HPLC-DAD). Foi constatado um aumento progressivo na concentração dos compostos analisados ao longo do período analisado, sendo que os compostos encontrados em maior concentração foram siringaldeído e ácido gálico.

Cachaça is a traditional and popular Brazilian drink obtained by distilling fermented sugar cane juice. Among the steps involved in its production, natural aging in wood containers for a certain period of time can lead to alterations in the chemical composition, aroma, flavor and color of the beverage. The present work sought to determine the concentration of phenolic compounds after different periods of aging of the cachaça in an oak (Quercus sp.) barrel. Periodic collections during the aging period were performed, and thirteen selected phenolic compounds were determined by high performance liquid chromatography with a diode-array detector (HPLC-DAD). A progressive increase in the concentration of the compounds analyzed was observed, with syringaldehyde and gallic acid as the compounds encountered in the highest concentration.