A gas chromatographic method for the determination of the fungicide chlorothalonil in tomatoes and cucumbers and its application to dissipation studies in experimental greenhouses

Abstract

Desenvolveu-se e validou-se um novo método para avaliar os níveis de resíduo e a dissipação do fungicida clorotalonil em tomates e pepinos cultivados em estufas experimentais. Os vegetais foram submetidos a uma única pulverização com clorotalonil em meia dose, dose recomendada e dobro da dose. Os resíduos de clorotalonil foram extraídos em sistema Ultra-Turrax empregando acetato de etila na presença de sulfato de sódio anidro e determinados por cromatografia gasosa com detecção por captura de elétrons. As curvas analíticas foram lineares de 0,005 a 5,0 mg L -1 , com coeficiente de determinação maior que 0,995. Os ensaios de precisão fornecem resultados aceitáveis com valores de RSD abaixo de 10,5% e recuperações entre 92,2 e 114,5% para tomate, e entre 86,2 e 103,3% para pepino, ambos obtidos para níveis de fortificação 0,028, 0,28, 2,8 e 5,0 mg kg -1. A interpretação estatística dos níveis de resíduo indicou um modelo de primeira ordem para o comportamento da dissipação do clorotalonil. O tempo médio de meia-vida para o tratamento na dose recomendada, nos dois anos experimentais, foram 8,8 dias para tomate e 1,6 dia para pepino. A taxa mais elevada da diminuição de resíduos de clorotalonil em pepino é devida, principalmente, à taxa de crescimento mais elevada deste vegetal com relação ao tomate. O método desenvolvido provou ser eficiente para a determinação de resíduos de clorotalonil em tomate e pepino até o nível de 0,02 mg kg -1 , permitindo avaliar o risco da exposição do consumidor.A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in tomatoes and cucumbers grown in experimental greenhouses was developed and validated. The vegetables were submitted to a single spraying with chlorothalonil at half, equal to and double of the recommended dose. Chlorothalonil residues were extracted in Ultra-Turrax system using ethyl acetate in the presence of anhydrous sodium sulphate and determined by gas chromatography with electron capture detection. The analytical curves were linear from 0.005 to 5.0 mg L -1 , with coefficient of determination higher then 0.995. The assays provide acceptable results with RSD values below 10.5% and recoveries were between 92.2 and 114.5% for tomatoes, and between 86.2 and 103.3% for cucumbers, both obtained from spiked samples at 0.028, 0.28, 2.8 and 5.0 mg kg -1 levels. Statistical interpretation of residue levels fitted to a first-order model for the dissipation behavior of chlorothalonil. The mean half-life after treatments at the recommended dose, in the two experimental years, was 8.8 days for tomatoes and 1.6 days for cucumbers. The higher decrease rate of chlorothalonil residues in cucumbers is mainly due to the higher growth rate of this vegetable relative to tomato. The developed method has proven to be efficient for the determination of chlorothalonil residues in tomatoes and cucumbers with a limit of quantification of 0.02 mg kg -1 level, permitting to evaluate the risk of consumer exposure to these residues.

Single‐step modified QuEChERS for determination of chlorothalonil in shallot (Allium ascalonicum) using GC‐μECD and confirmation via mass spectrometry

“…Kurz et al . () developed an analytical method for determination of chlorothalonil in tomato and cucumber using EtOAc as an extraction solvent without any further clean‐up, with the sample and solvent ratio maintained at 1: 4. A large amount of sample (25 g) with large volume of solvent (100 mL) was used.…”

“…During the QuEChERS procedure, dispersive SPE using primary secondary amine (PSA) sorbent is the most critical step for chlorothalonil losses, as it causes considerable pH increment. Kurz et al (2008) developed an analytical method for determination of chlorothalonil in tomato and cucumber using EtOAc as an extraction solvent without any further clean-up, with the sample and solvent ratio maintained at 1: 4. A large amount of sample (25 g) with large volume of solvent (100 mL) was used.…”

“…The recoveries were >80% with RSDs <7% in all commodities. Many studies (Fernandez‐Alba et al ., ; Kin et al ., ; Kurz et al ., ) describe a GC‐method using a classical detector (ECD) for determination of different pesticides, including chlorothalonil, in various commodities, obtaining recoveries between 80 and 100% for all pesticides. However, in these studies, large amounts of sample (25–30 g) were used, as well as large extraction solvent volumes (typically 100 mL).…”

Evaluation of QuEChERS Sample Preparation for Determination of Avermectins Residues in Ovine Muscle by HPLC-FD and UHPLC-MS/MS

“…Since Anastassiades et al 17 proposed QuEChERS (quick, easy, cheap, effective, rugged and safe), different versions have been published. Initially developed for pesticide residues extraction from fruits 18 and vegetables, 19 this method have been applied for veterinary drugs residues analysis in different food of animal origin as milk, 20 beef, 21,22 poultry, 23 honey, 24,25 sea food, 26 liver and eggs. [27][28][29] The most applied technique for determination of avermectins is the high performance liquid chromatography.…”

Analytical chemistry in Brazil: healthy and growing

“…Most research works found in literature have applied chromatography frequently associated with mass spectrometry. These works investigated different types of residues and products, such as sulfonamides 83 and streptomycin 84 in honey, buprofezin, tetradifon, vinclozolin, and bifenthrin in propolis, 85 glyphosate in soybeans, 86 chlorpyriphos, λ-cyhalithrin, cypermethrin, and deltamethrin in tomatoes, 87 chlorothalonil in tomatoes and cucumbers, 88 fenitrothion in tomatoes, 89 dimethoate, malathion, lufenuron, trichlorfon, carbofuran, 3-hydroxycarbofuran, difenoconazole, and thiabendazole in coconut pulp, 90 chlorpyriphos, cypermethrin, and fipronil in bovine plasma. 91 A non-chromatographic procedure was also developed for the determination of toxic arsenic species in vegetables using hydride generation-atomic fluorescence spectrometry.…”