Ricardo Dalla Villa

Sampling and analysis of pesticides in the gas phase of air: method validation using a volatilization chamber

This study evaluated the efficiency of Tenax® resin to sample the pesticides, atrazine, chlorpyrifos, α,β-endosulfan, metolachlor and trifluralin, from contaminated air in a volatilization chamber. The air contamination was performed by adding pesticide masses in the range of 100–750 ng in a chamber at an air flow rate of 2.60 L min−1 at 35 °C for 12 h. After volatilization, the pesticides followed the airflow toward the cartridges packed with two sequential sections of Tenax® resin, separated by glass wool. In this apparatus, the sampling efficiency remained between 82 and 119%, with RSD% lower than 14%. The method quantitation limit (MQL) was 53.4 ng m−3 for all studied analytes. Comparative trials with the resin XAD®-2 showed the sampling efficiency between 83 and 92%, with CV less than 10%. The volatilization chamber also allowed the evaluation of the volatilization profile of each analyte and helped in the sampling cartridge setting, in order to prevent the breakthrough effect.

Assessment of metolachlor and diuron leaching in a tropical soil using undisturbed soil columns under laboratory conditions

In the present study, diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-metoxi-1-methylethyl)acetamide] leaching was studied in undisturbed soil columns collected in a cotton crop area in Mato Grosso State, Brazil. The pesticides were applied to the soil surface in dosages similar to those used in a cotton plantation. To assess the leaching process, soil columns were submitted to simulated rain under laboratory conditions at 25 ± 3°C, in the absence of wind and direct solar radiation. During the rain simulations, leachate solutions were collected and herbicide concentrations were determined. At the end of the experiment, the soil columns were cut into 10 cm sections to determine the remaining herbicide concentrations through the soil profile. Metolachlor was detected in all soil sections, and approximately 4% of the applied mass was leached. Diuron was detected only in the upper two soil sections and was not detected in the leachate. A linear correlation (r > 0.94) between the metolachlor soil concentrations and the organic contents of the soil sections was observed. Mass balance suggests that around 56% of diuron and 40% of metolachlor were degraded during the experiments. Measurements of the water table depth in the area where the samples were collected showed that it varied from 2 to 6 m and is therefore vulnerable to contamination by the studied herbicides, particularly metolachlor, which demonstrated a higher leaching potential.

Liquid–liquid extraction as a sample preparation procedure for the determination of Na, K, Ca, and Mg in biodiesel

Liquid–liquid extraction is proposed as a clean sample preparation procedure for the determination of Na, K, Ca, and Mg in biodiesel by line source flame atomic absorption spectrometry (LS FAAS) and of Na and K by flame photometry (FP). A full 23 factorial design was used to optimize the sample preparation. The investigated variables were the temperature effect, the use of acid and the stirring time for the extraction of metals in biodiesel. The sample preparation method essentially consisted of extracting metals from biodiesel with an aqueous solution of HNO3 (1%, v/v) at 25 °C and manual agitation for 4 min. The instrumental limits of detection (LODs) for LS FAAS and FP were in the ranges 0.04–0.21 and 0.18–0.36 mg kg−1, respectively. The accuracy of the method was checked by means of addition and recovery tests, and the recovery results for LS FAAS and FP varied from 80 to 114%, with RSD less than 14%. No significant differences were observed (p = 0.05) between the results obtained by the proposed technique and a comparative method. Interlaboratory studies were performed using different instruments, different samples and the same analyst. For this, addition and recovery tests and CRM analyses were performed by high resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and FP. The recoveries varied from 84 to 107%, with RSD less than 11% and the results for Na, K, Ca and Mg were in agreement with the certified values at the 95% confidence level (t-test; p < 0.05). The findings indicate that the liquid–liquid extraction method is reproducible, simple, and clean, and can be used as an alternative method of sample preparation for the determination of Na, K, Ca, and Mg in biodiesel samples.

Microextração líquido-líquido dispersiva assistida por vortex e ultrassom aplicada à determinação de agrotóxicos triazinas, triazinonas e o triazol flutriafol em água

This study aimed at developing and validating a method for the simultaneous determination of triazines (ametryne, atrazine, prometryne and terbuthylazine), triazinones (metribuzin and hexazinone) and a triazole (flutriafol) in water by ultrasound vortex assisted dispersive liquid-liquid microextraction (USVADLLME) and GC-MS. The experimental conditions that provided the best results were: 5.00 mL of sample, 100 mL of extractor solvent (toluene), vortex agitation for 30 s and sonication for 1 min. at 240 W and 40 oC. The USVADLLME provided recoveries ranging from 77.2% to 109%, with a repetitivity and intermediate precision varying from 1.4 to 9.0% and 2.9 to 15%, respectively. The method detection limits ranged between 0.10 and 2.71 µg L-1. The method was applied to different surface water samples and a matrix effect was not observed. Once validated, the proposed method was applied to ten water samples of an important agricultural region of Mato Grosso State/Brazil, but none of the studied analytes were detected. The USVADLLME is proposed as an efficient, fast, simple and non-expensive alternative technique for the simultaneous determination of multiclass pesticides in water.

Método Analítico Multiclasses Para Determinação de Agrotóxicos Em Água Utilizando DLLME e CG-MS

This work aimed to develop and validate a method for the determination of trifluralin, metribuzin, metolachlor, endosulfan, -cyhalothrin, permethrin and malathion in water using dispersive liquid-liquid microextraction (DLLME). The mixture n-hexane/toluene (60:40 v/v) showed high extraction capacity and was used in the method validation. The method was applied to different surface water samples and a matrix effect was not observed. The DLLME provided recovery of 47–115 % with a RSD up to 16%. The detection limits ranged between 0.0063 and 0.046 μg L whereas the method quantitation limit was 2.0 μg L for all analytes. After validated, the method was applied to water samples collected in an agricultural region of Mato Grosso State, Brazil and only permethrin was detected. The proposed method can be an alternative for the simultaneous determination of multiclass pesticides in water, with the advantage of being fast and using a very small amount of solvent.Este trabalho teve como objetivo desenvolver e validar um metodo para a determinacao da trifluralina, metribuzin, metolacloro, endosulfan, ? -cialotrina, permetrina e malathion em agua usando microextracao liquido-liquido dispersiva (DLLME). A mistura de n-hexano / tolueno (60:40, v / v) mostrou elevada capacidade de extracao e foi utilizada na validacao do metodo. O metodo foi aplicado diferentes amostras de agua superficial e nao foi observado um efeito matriz. A DLLME proporcionou uma recuperacao de 47-115% com um RSD de ate 16%. Os limites de deteccao variaram entre 0,0063 e 0,046 mg L -1 enquanto que o limite de quantificacao do metodo foi de 2,0 mg L -1 para todos os analitos. Depois de validado, o metodo foi aplicado em amostras de agua coletadas em uma regiao agricola de Mato Grosso, Brasil e somente a permetrina foi detectada. O metodo proposto pode ser uma alternativa para a determinacao simultânea de pesticidas multiclasses em agua, com a vantagem de ser rapido e utilizar uma pequena quantidade de solvente.

Composição centesimal e mineral de plantas medicinais comercializadas no mercado do Porto de Cuiabá, Mato Grosso, Brasil

The purpose of this study was to determine the proximal (ash, moisture, protein, lipids, and total carbohydrates) and mineral (Na, K, Ca, Cu, Fe, Mg, Mn, and Zn) composition of the medicinal plants barbatimao (Stryphnodendron adstringens (Mart.) Coville), carqueja (Baccharis trimera (Less) D.C.), mangava-brava (Lafoensia pacari A. St.-Hil.), pau-tenente (Quassia amara L.), and quebra pedra (Phyllanthus niruri L.), commercialized in the Cuiaba Port Market in Mato Grosso. The samples were botanically identified by the voucher specimen grown in the Botanical Institute of the Federal University of Mato Grosso, at the Cuiaba campus. Proximal composition was determined according to the recommendations of the Association of Official Analytical Chemists and the concentration of minerals was quantified by flame atomic absorption spectrometry. The results obtained were: moisture content (7.72% to 12.10%); ashes (1.64% to 8.44%); protein (2.36% to 9.35%); lipids (0.41% to 2.05%), and total carbohydrates (72.09% to 82.37%), and significant differences were found between the samples (p≥0.05). The mineral concentrations varied from 0.01 to 21.57 mg/g in the plants and 0.01 to 32.17 mg/200mL in the infusions. No significant differences (p≥0.05) were found between the samples for mineral composition, except for K, Ca, and Mg. The mineral extraction capacity of the dry matter for infusions was as follows: Na>K>Zn>Cu>Mg>Mn>Ca>Fe. The daily index values of the metal species quantified in 200 mL infusions suggest that teas can be a source of minerals, especially K and Mn.

Câmara de volatilização: uma alternativa para avaliação da eficiência de amostragem de α- e β -endossulfam em fase gasosa

The efficiency of XAD®-2 resin in sampling the pesticides α and β-endosulfan from air contaminated in the laboratory was evaluated. Sampling efficiency ranged from 87 to 108% for α-endosulfan and from 71 to 84% for β-endosulfan with relative standard deviation lower than 19%. The pesticides were not detected in the second section of the cartridge showing the good retention capacity of XAD®-2 for these analytes. Method quantification limits were 0.32 and 0.34 µg m-3 for α and β-endosulfan, respectively. These results suggest that the proposed method may be useful for evaluating occupational exposure to these compounds.