RESUMO

This paper reports the electrosynthesis and characterisation of a polymeric film derived from 2-hydroxybenzamide over a graphite electrode and its application as an enzymatic biosensor for the determination and quantification of the pesticide fenitrothion. The material was analysed by scanning electron microscopy and its electrochemical properties characterised by cyclic voltammetry and electrochemical impedance spectroscopy. The enzyme tyrosinase was immobilised over the modified electrode by the drop and dry technique. Catechol was determined by direct reduction of biocatalytically formed o-quinone by employing the flow injection analysis technique. The analytical characteristics of the proposed sensor were optimised as follows: phosphate buffer 0.050 M at pH 6.5, flow rate 5.0 mL min-1, sample injection volume 150 µL, catechol concentration 1.0 mM and maximum inhibition time by fenitrothion of 6 min. The biosensors showed a linear response to pesticide concentration from 0.018 to 3.60 µM. The limit of detection and limit of quantification were calculated as 4.70 nM and 15.9 nM (RSD < 2.7%), respectively. The intra- and inter-electrode RSDs were 3.35% (n = 15) and 8.70% (n = 7), respectively. In addition, water samples spiked with the pesticide showed an average recovery of 97.6% (±1.53).

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The practice of large-scale agriculture requires the use of pesticides in order to maximize production. This activity has gained increasing attention in recent years, especially from rural workers, due to the risks associated with long-term exposure to pesticides. To minimize these risks, personal protection equipment (e.g., covers, gloves, and goggles) and collective protection equipment (e.g., agricultural tractors with sealed cabins) have been developed. In general, these approaches are intended to reduce the contact of farmers and agricultural machinery operators with the more toxic and stable compounds, an example of which is fenitrothion. In this study, fenitrothion was used as a marker to evaluate the protection afforded inside a sealed tractor cabin. To simulate the pesticide exposure, tests were performed using artificial cotton targets as passive adsorptive agents inside the cabin during the pesticide application. Samples were extracted according to the US Environmental Protection Agency (USEPA) procedure using ultrasonic extraction and as proposed by the Brazilian Standard for Solid Waste Classification (NBR 10004). The extracts were analyzed by high-performance liquid chromatography with diode array detection (HPLC-DAD). The chromatographic method was optimized using a factorial design. The combined results indicated that the best conditions were achieved using a mobile phase with a water/acetonitrile ratio of 35:65, a column temperature of 40 °C, and a flow rate of 1.0 mL/min, with a total analysis time of <10 min. The method was evaluated in the linear range of 0.50 to 2.01 mg/kg, with a determination coefficient of 0.9886. The precision was evaluated on different days and the relative standard deviations were between 0.17 and 3.41 %. In relation to the accuracy, recovery values of 95 to 104 % were obtained. The detection and quantification limits were 0.18 and 0.50 mg/kg, respectively. None of the target cottons showed concentrations of fenitrothion above the limit of detection of 0.18 mg/kg.

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Deltamethrin-based campaigns to control Triatoma infestans (Klug) (Hemiptera: Reduviidae) have decreased in success as a result of the development of insecticide resistance. We compared the in vitro effects of the pyrethroid deltamethrin and two doses of the organophosphate fenitrothion, presented on different materials, on T. infestans from La Esperanza, Argentina. Laboratory tests demonstrated a decrease in susceptibility to deltamethrin in the field population [LD50 : 30.32 nanograms per insect (ng/i)] compared with the reference population (LD50 : 0.13 ng/i), giving a high resistance ratio of 233.42. By contrast, similar susceptibility to fenitrothion was assessed in both the field and reference populations (LD50 : 21.65 ng/i and 21.38 ng/i, respectively). The effectiveness of the formulated insecticides varied according to the surfaces to which they were applied. The application of fenitrothion formulations to glass or brick resulted in mortality of 90-100%. The application of fenitrothion formulations to wood or mud caused mortality in the range of 6.7-56.7%. Resistant insects presented low mortality when exposed to the deltamethrin formulation and high mortality when exposed to fenitrothion formulations. Moreover, the insecticides demonstrated residual activity only when applied to glass. The present work demonstrates that fenitrothion is an alternative to pyrethroids for the management of deltamethrin-resistant insects in La Esperanza. However, this effectiveness is not sustained over time.

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Introducción: Panstrongylus geniculatus es un triatomino silvestre, vector del Trypanosoma cruzi, intruso en domicilios humanos. Determinar la susceptibilidad a insecticidas de uso común en esta especie es indispensable para detectar prematuramente cepas resistentes. Objetivo: Este estudio se propuso analizar la susceptibilidad a lambdacihalotrina y fenitrotión en dos cepas (laboratorio y campo) de P. geniculatus. Metodología: se estableció la susceptibilidad a lambdacihalotrina y fenitrotión por aplicación tópica, en la cepa de laboratorio-Molagavita 2003 y en la población de campo-Chorreras 2012 en ninfas del primer estadio de P. geniculatus. Se calcularon valores de dosis letal 50 y dosis letal 99 (DL50 y la DL99) para cada insecticida. También se determinaron valores de grado de resistencia (GR) para cada insecticida: DL50 población de campo/DL50 cepa de laboratorio. Resultados: Las DL50 y DL99 en la población de campo y la cepa de laboratorio (en ng/i), fueron: 1,194; 5,764 y 0,024; 0,131 para lambdacihalotrina y 1,476; 7,354 y 0,482; 5,471 para fenitrotión, respectivamente. Los grados de resistencia fueron: GR= 48,9 para lambdacihalotrina y GR= 3,06 para fenitrotión. Conclusiones: La población de campo mostró resistencia a lambdacihalotrina y fenitrotión, probablemente como consecuencia del uso de agroquímicos en la zona. Implementar medidas para la detección temprana de resistencia en triatominos es importante en el diseño de programas de control vectorial.

Introduction: Panstrongylus geniculatus, is a wild triatomine, vector of Trypanosoma cruzy, intruder in human homes. To determine the susceptibility to insecticides commonly used in this specie is essential to detect resistant strains prematurely. Objective: This study aimed to analyze the susceptibility to lambdacyhalothrin and fenitrothion in two strains (laboratory and field) of P. geniculatus. Methodology: susceptibility was established to lambdacyhalothrin and fenitrothion by topical application in the laboratory strain - Molagavita 2003 and field population - Chorreras 2012 in first instar nymphs of P. geniculatus. Values were calculated for lethal dosis 50 and lethal dosis 99 (LD50 and LD99) for each insecticide. Also values were determined to degree of resistance (GR) for each insecticide: field population LD50/LD50 laboratory strain. Results: The LD50 and LD99 in the field population and the laboratory strain (in ng/i) were: 1,194, 5,764 and 0,024, 0,131 for lambdacyhalothrin and 1,476, 7,354 and 0,482, 5,471 to fenitrothion, respectively. The degrees of resistance were: GR=48.9 for lambdacyhalothrin and GR=3.06 for fenitrothion. Conclusions: The field population showed resistance to lambdacyhalothrin and fenitrothion, probably as a result of the use of chemicals in the area. Implement measures for early detection of resistance in triatomines is important in the design of vector control programs.

RESUMO

Several agrochemicals like organophosphates are extensively used to control pests in agricultural practices but they also adversely affect non-target fauna. The effect of organophosphorous fenitrothion on the prawn Macrobrachium borellii was evaluated. The 96-h LC50 was determined. Activity of superoxide dismutase, catalase, glutathione-S-transferase and lipid oxidation levels, were evaluated in the hepatopancreas from adults exposed to sublethal fenitrothion concentrations for 1, 2, 4 and 7 days. In addition, superoxide dismutase mRNA expression, acetylcholinesterase inhibition and haemocyte DNA damage were determined. The 96-h LC50 was 4.24µg/l of fenitrothion. Prawn exposed to sublethal FS concentrations showed an increase of both catalase and superoxide dismutase activities, mainly after 2 and 4 days exposure and an increase of glutathione-S-transferase activity from day 2 to day 7 while lipid oxidation levels increased mainly on day 1. Superoxide dismutase transcripts were significantly higher in fenitrothion -treated prawns, indicating an induction mechanism. Hemolymph analysis showed that while acetylcholinesterase activity decreased after 2 days, haemocytes displayed most DNA damage after 7-day exposure to fenitrothion. These results indicate that prawn enzymes are highly sensitive to fenitrothion exposure, and these biological responses in M. borellii could be valuable biomarkers to monitor organophosphorous contamination in estuarine environments.

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Triatoma infestans (Klug) is the main vector of Chagas disease, which is a public health concern in most Latin American countries. The prevention of Chagas disease is based on the chemical control of the vector using pyrethroid insecticides. In the last decade, different levels of deltamethrin resistance have been detected in certain areas of Argentina and Bolivia. Because of this, alternative non-pyrethroid insecticides from different chemical groups were evaluated against two T. infestans populations, NFS and El Malá, with the objective of finding new insecticides to control resistant insect populations. Toxicity to different insecticides was evaluated in a deltamethrin-susceptible and a deltamethrin-resistant population. Topical application of the insecticides fenitrothion and imidacloprid to first nymphs had lethal effects on both populations, producing 50% lethal dose (LD50) values that ranged from 5.2-28 ng/insect. However, amitraz, flubendiamide, ivermectin, indoxacarb and spinosad showed no insecticidal activity in first instars at the applied doses (LD50 > 200 ng/insect). Fenitrothion and imidacloprid were effective against both deltamethrin-susceptible and deltamethrin-resistant populations of T. infestans. Therefore, they may be considered alternative non-pyrethroid insecticides for the control of Chagas disease.

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Fenitrothion is an organophophorus insecticide of moderate toxicity to mammals, which is used in agriculture to control insects on some cultures and on stored grains. ANVISA/ Brazilian Ministry of Health established the fenitrothion maximum limit residue (MLR) of 1.0mg/kg in wheat. The aim of this investigation was to verify this compound residues in white wheat flour to comply the São Paulo State Health Programme Programa Paulista 2006. For this purpose a survey of fenitrothion residues was carried out in 62 flour samples from varied market sites and bakeries of São Paulo State, collected by Sanitary Surveillance Service from April to June 2006. Fenitrothion residues were determined by means of gas chromatography with flame photometric detection (GC-FPD). Recovery studies were performed at two different levels, 0.05 e 0.50mg/kg, and the mean recoveries on the established levels were between 93% - 113% and 78% - 91%, respectively. The limit of detection was estimated as 0.02mg/kg, and the limit of quantification was 0.05mg/kg. The data showed values of fenitrothion lower than the established MRL to wheat (1.0mg/kg), which corroborate the needs to establish MRL for processed products, such as wheat flour. MRLs are the basis for calculating the daily dietary consumption of pesticides. They also provide factual data for estimating the daily pesticide residue intake by a person t

A fenitrotiona é um inseticida organofosforado de toxicidade moderada para mamíferos, usado para o controle de insetos em algumas culturas e em grãos armazenados. No Brasil, seu limite máximo de resíduo (LMR) em trigo estabelecido pela ANVISA/MS é 1,0mg/kg. Com a finalidade de verificar seus resíduos em farinha de trigo branca atendendo o Programa Paulista 2006, foram analisadas 62 amostras coletadas no período de abril a junho de 2006 pela Vigilância Sanitária do Estado de São Paulo, em vários pontos de comércio e padarias do estado. A fenitrotiona foi determinada por cromatografia em fase gasosa com detector fotométrico de chama (FPD). Foram realizados estudos de recuperação em dois níveis, 0,05 e 0,50mg/kg, cujos resultados variaram de 93% a 113% e 78% a 91%, respectivamente. O limite de detecção do método foi 0,02mg/kg e o de quantificação foi 0,05mg/kg. Os dados obtidos são inferiores ao LMR vigente para trigo de 1,0mg/kg e corroboram a importância do estabelecimento de LMR para produtos processados, neste caso, a farinha de trigo. Os LMR são a base para o cálculo do consumo diário dos pesticidas, proporcionando dados mais realistas para o cálculo da quantidade de resíduos de pesticidas realmente ingeridos por uma pessoa consumindo uma dieta que lhe é habitual (Ingestão Diária Aceitável).

RESUMO

The behavior of fenitrothion in fruits and leaves of staked tomato plants was studied with gas chromatography. The field experiment begun when plants had 90 days post-transplant and consisted of four treatments: (1) a single application of fenitrothion at 100 g a.i./100 liters of water; (2) a double dose application of 200 g a.i./100 liters of water; (3) four applications at 7 day intervals at the lower dosage; and (4) control. Fruit and leaf samples were collected one day before application (-1) and at zero, 1, 2, 3, 5, 7 and 14 days post-application. Residual analysis of fruit and leave consisted of acetone extraction and partition with chloroform; extract cleaning in a florisil column and benzene elution (for leaves). Quantitative estimates were obtained in a gas chromatograph, using flame photometric detector, with a special phosphorus filter. Leaf residues were always higher than those in fruits (approximately 80 times), during all sampling intervals. Half-live degradation values of fenitrothion in fruits and leaves were: 1.6 to 1.9 and 0.7 to 0.8 days, respectively. Half-lives of persistence were similiar for both substrates: 4.2 to 7.3 and 5.6 to 6.2 days, respectively. Fruit residues immediately after application were below the official tolerance level (0.5 ppm) for treatments of 100 g a.i./100 liters in one or four weekly applications. A single application of 200 g a.i./100 liters resulted in residual levels lower than 0.5 ppm after one or more days post-application.

Estudou-se o comportamento dos resíduos de fenitrotion em frutos e folhas de tomateiro estaqueado, através de cromatografia gasosa. O experimento de campo foi instalado quando as plantas tinham 90 dias após o transplante das mudas, e constou de quatro tratamentos: (1) uma aplicação de fenitrotion em dosagem simples, de 100 g i.a./100 litros de água, (2) uma aplicação em dosagem dobrada, de 200 g i.a./100 litros de água, (3) quatro aplicações espaçadas de sete dias, na dosagem simples e (4) testemunha. As amostras de fruto e folha foram colhidas um dia antes da aplicação (-1) e aos zero , 1, 2, 3, 5, 7 e 14 dias após. Basicamente, a metododogia para análises dos resíduos dos frutos e das folhas constou da extração com acetona e partição em clorofórmio; limpeza dos extratos em coluna de florisil (no caso de folhas) e eluição procedida com benzeno. As determinações quantitativas foram feitas por cromatografia gasosa, usando-se detector fotométrico de chama com filtro específico para fósforo. Os resíduos nas folhas foram sempre maiores do que os dos frutos (cerca de 80 vezes, em média) durante todo o período de colheita das amostras. Os valores de meia-vida de degradação de fenitrotion em frutos e folhas foram: 1,6 a 1,9 e 0,7 a 0,8 dia, respectivamente, mostrando uma diminuição mais rápida dos resíduos em folhas. As meias-vidas de persistência foram semelhantes para os dois substratos: 4,2 a 7,3 e 5,6 a 6,2 dias, respectivamente. Os resíduos encontrados nos frutos logo após a aplicação, foram menores que a tolerância oficial (0,5 ppm) para os tratamentos que utilizaram 100 g i.a./100 litros em uma ou quatro pulverizações espaçadas de sete dias. Uma única aplicação de 200 g i.a./100 litros resultou em resíduos menores que 0,5 ppm, desde um dia após a aplicação.

RESUMO

The behavior of fenitrothion in fruits and leaves of staked tomato plants was studied with gas chromatography. The field experiment begun when plants had 90 days post-transplant and consisted of four treatments: (1) a single application of fenitrothion at 100 g a.i./100 liters of water; (2) a double dose application of 200 g a.i./100 liters of water; (3) four applications at 7 day intervals at the lower dosage; and (4) control. Fruit and leaf samples were collected one day before application (-1) and at zero, 1, 2, 3, 5, 7 and 14 days post-application. Residual analysis of fruit and leave consisted of acetone extraction and partition with chloroform; extract cleaning in a florisil column and benzene elution (for leaves). Quantitative estimates were obtained in a gas chromatograph, using flame photometric detector, with a special phosphorus filter. Leaf residues were always higher than those in fruits (approximately 80 times), during all sampling intervals. Half-live degradation values of fenitrothion in fruits and leaves were: 1.6 to 1.9 and 0.7 to 0.8 days, respectively. Half-lives of persistence were similiar for both substrates: 4.2 to 7.3 and 5.6 to 6.2 days, respectively. Fruit residues immediately after application were below the official tolerance level (0.5 ppm) for treatments of 100 g a.i./100 liters in one or four weekly applications. A single application of 200 g a.i./100 liters resulted in residual levels lower than 0.5 ppm after one or more days post-application.

Estudou-se o comportamento dos resíduos de fenitrotion em frutos e folhas de tomateiro estaqueado, através de cromatografia gasosa. O experimento de campo foi instalado quando as plantas tinham 90 dias após o transplante das mudas, e constou de quatro tratamentos: (1) uma aplicação de fenitrotion em dosagem simples, de 100 g i.a./100 litros de água, (2) uma aplicação em dosagem dobrada, de 200 g i.a./100 litros de água, (3) quatro aplicações espaçadas de sete dias, na dosagem simples e (4) testemunha. As amostras de fruto e folha foram colhidas um dia antes da aplicação (-1) e aos zero , 1, 2, 3, 5, 7 e 14 dias após. Basicamente, a metododogia para análises dos resíduos dos frutos e das folhas constou da extração com acetona e partição em clorofórmio; limpeza dos extratos em coluna de florisil (no caso de folhas) e eluição procedida com benzeno. As determinações quantitativas foram feitas por cromatografia gasosa, usando-se detector fotométrico de chama com filtro específico para fósforo. Os resíduos nas folhas foram sempre maiores do que os dos frutos (cerca de 80 vezes, em média) durante todo o período de colheita das amostras. Os valores de meia-vida de degradação de fenitrotion em frutos e folhas foram: 1,6 a 1,9 e 0,7 a 0,8 dia, respectivamente, mostrando uma diminuição mais rápida dos resíduos em folhas. As meias-vidas de persistência foram semelhantes para os dois substratos: 4,2 a 7,3 e 5,6 a 6,2 dias, respectivamente. Os resíduos encontrados nos frutos logo após a aplicação, foram menores que a tolerância oficial (0,5 ppm) para os tratamentos que utilizaram 100 g i.a./100 litros em uma ou quatro pulverizações espaçadas de sete dias. Uma única aplicação de 200 g i.a./100 litros resultou em resíduos menores que 0,5 ppm, desde um dia após a aplicação.