ABSTRACT An adequate combination of factors involved in the technology used for phytosanitary product application contributes to an efficient spray deposition on the target. The objective of this study was to use multivariate analysis to characterize the magnitude of effects and the order of influence of three factors that interfere with the quality of phytosanitary product application in coffee plants. An entirely randomized design was adopted, with four repetitions, using a 2 × 2 × 3 factorial scheme, with two classes of droplets quality (fine and coarse), two application rates (250 and 400 L ha-1), and the use of adjuvants (with no adjuvant or with Fighter®and Aureo® adjuvants). The quality of the application was determined by jointly analyzing the spray deposition on three thirds of leaves, in their internal and external layers, the runoff to soil, coverage, droplet density, relative amplitude, and the volumetric median diameter. The results underwent analysis of variance (ANOVA) to measure the effect sizes (η2). After testing the assumptions of multivariate analysis, clustering and principal component analyses were performed. The class of droplets was found to be the most influential factor in the quality of the phytosanitary product application (spray deposition and runoff to soil). When focusing on spray deposition on leaves, the second-most influential factor was the application rate and the relation between the application rate and the adjuvants. For the other variables, the second-most influential factor was the application rate.

ABSTRACT It is a well-known fact that the application of pesticides can be improved using an electrostatic spray due to the reduction of the application rate and increase in deposition on plant targets. However, little information exists on the use of such technology in maize crops. Thus, this study is aimed to evaluate the spray deposition on maize resulting from spray application using an electrostatic sprayer in combination with low application rates and different spray compositions. A field experiment was conducted in a randomized block having a 2×2×2 factorial design with two application rates (95 and 52 L ha-1), with or without the spray electrification, and with or without the synthetic adjuvant. The droplet electrification ability, interference of the electrical conductivity of the spray solution, losses of spray solution to the soil, and spray deposition on maize plants were evaluated for two cases of insecticide applications. The Faraday cage method was used to determine the spray electrification ability of the equipment. The spray deposition on plants and the losses to the soil were analyzed using a tracer (food coloring dye) added to the spray solution that was subsequently detected by spectrophotometry. It was seen that the electrostatic sprayer improved the spray application efficiency, which responded positively to the increase in the electrical conductivity of the spray solution. The deposition of the electrified spray solution on the upper third canopy of maize was found to be higher; the spray solution electrification also reduced the losses to the soil, regardless of the application rate.

ABSTRACT Electrostatic spray can bring benefits to the pesticide application such as the reduction of application rate and the increase of deposits on targets. Therefore, this study aimed to evaluate the effect of electrostatic spraying using lower application rates and different adjuvants on soybean spray deposition and chemical control of powdery mildew (Microsphaera diffusa Cooke & Peck). The field experiment was conducted in duplicate. A randomized complete block design with four replications in a 2 × 2 × 2 + 1 factorial scheme was used. The factors were two application rates, with and without droplet electrification, two spray solution compositions, and one additional treatment. Deposition on upper and lower leaves, spray loss to the soil, and powdery mildew control effectiveness were evaluated. The electrical conductivity of the spray solution and the charge/mass ratio induced in droplets were also evaluated. All treatments reduced the soybean powdery mildew severity. Electrostatic spraying responded positively to an increase in the electrical conductivity of the spray solution regarding the charge/mass ratio, but it did not increase spray deposition on the lower third of the canopy and did not influence spray loss to the soil, which was higher as the application rate increased.

ABSTRACT Knowledge of droplet spectra generated by spray nozzle tips is important to ensure the quality of applications of plant protection products. However, there are different methods for this evaluation, which can cause difficulty in interpreting the results. This study aimed to evaluate the droplet spectra produced by the flat fan spray tip AD 11002 operated under different pressures and using different techniques and equipment. The volume median diameter (VMD), percentage of spray volume in droplets smaller than 100 µm diameter and relative spam (RS), considering pressures of 200, 300, and 400 kPa were determined using two direct measurement equipment (Spraytec and Shadow Sizer), based on laser diffraction and image analysis, respectively, and a measure based on indirect analysis, through the digitization of water-sensitive paper. Thus, the use of different analysis techniques led to variations of the analyzed parameters. Among the direct measurement equipment, a difference of up to 58% was observed in VMD. The use of water-sensitive paper to characterize droplet spectra must be carried out with great discretion because there is an underestimation of fine droplets. Pressure variations of 200 to 400 kPa did not influence VMD and RS.

O comportamento eletroquímico e a determinação de um bisfosfonato, o etidronato de sódio, em três diferentes eletrodos de cobre: eletrodo de cobre policristalino (CE) e eletrodos de pasta de carbono modificados com micropartículas de cobre (m-CPE) e nanopartículas de cobre (n-CPE) foi investigado. Usando o eletrodo CE, os voltamogramas apresentaram um pico de corrente anódica, enquanto com m-CPE e n-CPE, foram observados dois picos de corrente de oxidação. A densidade de corrente anódica em 610 mV para n-CPE é cinco vezes maior do que para m-CPE. Isto está relacionado ao efeito do tamanho das nanopartículas de cobre. As correntes anódicas foram relacionadas à oxidação eletrocatalítica do etidronato via eletrogeração de espécies ativas de Cu(III) em um mecanismo EC'. Os valores para a constante de velocidade catalítica para o processo de oxidação e o coeficiente de difusão do etidronato foram 8,9 × 103 cm³ mol-1 s-1 e 1,55 × 10-6 cm² s-1, respectivamente. Um procedimento sensível e rápido foi desenvolvido para a análise de etidronato, e os parâmetros analíticos correspondentes foram relatados. O etidronato foi determinado com um intervalo linear de 10,57 μmol L-1 e um limite de detecção de 200-2538 μmol L-1. A exatitude foi checada pela aplicação do teste de recuperação nas amostras. O método amperométrico proposto foi aplicado à análise de comprimidos farmacêuticos comerciais e os resultados apresentaram concordância com os valores de literatura.

The electrochemical behavior and determination of a bisphosphonate drug, sodium etidronate, on three different copper-based electrodes: polycrystalline copper electrode (CE) and copper microparticles- (m-CPE) and copper nanoparticles (n-CPE)-modified carbon paste electrodes was investigated. In the voltammograms recorded using CE, one anodic peak was appeared while, both m-CPE and n-CPE represented two anodic oxidation peaks. The anodic current density at 610 mV for n-CPE is >5 times higher that of m-CPE. This was related to the nanosize effect of copper nanoparticles. The anodic currents were related to the electrocatalytic oxidation of etidronate via the electrogenerated active species of Cu(III) in an EC' mechanism. The catalytic rate constant for the oxidation process and the diffusion coefficient of etidronate were obtained as 8.9×10³ cm³ mol-1 s-1 and 1.55×10-6 cm² s-1, respectively. A sensitive and time-saving sensing procedure was developed for the analysis of etidronate, and the corresponding analytical parameters were reported. Etidronate was determined with a limit of detection of 10.57 μmol L-1 with a linear range of 200-2538 μmol L-1. Accuracy was also checked by recovery test on spiked samples. The proposed amperometric method was applied to the analysis of commercial pharmaceutical tablets and the results were in good agreement with the declared values.

O comportamento eletroquímico da deferiprona, droga anti-talassêmica e anti-replicação do HIV foi investigado, por voltametria cíclica (VC), utilizando um eletrodo de platina. Observaram-se dois picos anódicos irreversíveis para a deferiprona, em tampão acetato (pH 4,0) com E(0)1 = 875 mV e E(0)2 = 1235 mV (vs. Ag/AgCl) em velocidade de varredura de 50 mV s-1. Os estudos de voltametria cíclica indicaram que o processo de oxidação é irreversível e controlado por difusão. Foram encontrados, para a deferiprona, coeficientes de difusão e de transferência de elétrons de 3,50 × 10-6 cm² s-1 e 0,57, respectivamente. Foi desenvolvido um procedimento sensível, simples e rápido, utilizando voltametria de pulso diferencial. Utilizando este método, a deferiprona pode ser determinada com um limite de detecção de 1,43 × 10-5 mol L-1. É descrita a aplicabilidade do método em ensaios diretos em soro humano enriquecido, fluidos urinários e em comprimidos comerciais.

The electrochemical behavior of the anti-thalassemia and anti-HIV replication drug, deferiprone, was investigated by cyclic voltammetry (CV) at a platinum electrode. In an acetate buffer solution, pH = 4.0, two irreversible anodic peaks for deferiprone, with E(0)1 = 875 mV and E(0)2 = 1235 mV (vs. Ag/AgCl) appeared at a potential sweep rate of 50 mV s-1. Cyclic voltammetric study indicated that the oxidation process is irreversible and diffusion-controlled. The diffusion and the electron transfer coefficients of deferiprone were found to be 3.50 × 10-6 cm² s-1 and 0.57, respectively. A sensitive, simple and time-saving differential pulse voltammetric procedure was developed. Using our proposed method, deferiprone can be determined with a detection limit of 1.43 × 10-5 mol L-1. The applicability of the method to direct assays of spiked human serum and urine fluids, and to commercial tablets, is described.