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Estimation of Residue Degradation of Cypermethrin and Chlorpyrifos in Brinjal, Tomato and Cauliflower Under Supervised Field Trial

Md. Sultan Ahmed
Division of Entomology, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur-1701, Bangladesh.

Debasish Sarker
Division of Entomology, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur-1701, Bangladesh.

Marina Afroze
Division of Entomology, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur-1701, Bangladesh.

Afroza Begum
Division of Entomology, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur-1701, Bangladesh.

Mohammad Dalower Hossain Prodhan
Division of Entomology, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur-1701, Bangladesh.

Abstract/ Executive Summary:

A study was carried out to detect and estimate the residue of cypermethrin and chlorpyrifos in brinjal, tomato, and cauliflower using Gas Chromatography (GC) coupled with Electron Capture Detector (ECD) and Flame Thermionic Detector (FTD). Three supervised field trials were conducted and sprayed with the recommended dose of cypermethrin (1 ml/L of water) and chlorpyrifos (3 ml/L of water) in three vegetables by knapsack sprayer. Samples were collected at 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 days after spray (DAS). The quantity of cypermethrin residue was above EU-MRLs (Maximum Residue Limit set by European Union) up to 4 DAS with 0.538 mg/kg in cauliflower; 3 DAS with 0.508 mg/kg in brinjal and 0.695 mg/kg in tomato. The quantity decreased down 0.328-0.019 mg/kg in cauliflower (4-9 DAS); 0.098-0.012 mg/kg (4-7 DAS) in brinjal and 0.458-0.022 mg/kg (4-7 DAS) in tomato which were below EU-MRLs (0.5 mg/kg). The quantity of chlorpyrifos residue was above EU-MRLs up to 9 DAS with 0.012 mg/kg in cauliflower but in brinjal and tomato, the detected quantities were above EU-MRLs up to 7 DAS with 0.029 mg/kg and 0.017 mg/kg residue. No residue was detected from brinjal and tomato samples collected at 8 DAS. But in cauliflower, no residue was detected at 10 days after spray. So, brinjal, tomato, and cauliflower can be harvested safely at 4 DAS and 5 DAS for cypermethrin, and in the case of chlorpyrifos, it was 8 DAS in brinjal and tomato and 10 DAS in cauliflower.

Keywords: Residue; Degradation; Chlorpyrifos; Cypermethrin; MRL; Gas chromatography

Location: Entomology Division, Bangladesh Agricultural Research Institute Gazipur (BARI).

Start Date:

End Date:

Program Area: Pest Management

Commodity: Vegetables

Objectives:

To estimate the amount and degradation rate of the residue of two commonly used insecticides in brinjal, tomato, and cauliflower.

Methodology:

The present study was conducted at Pesticide Analytical Laboratory and field of Entomology Division, Bangladesh Agricultural Research Institute Gazipur (BARI). The insecticide standard for chlorpyrifos and cypermethrin was obtained from Sigma-Aldrich Laborchemikalien, Gmbh P O Box-100262 D-30918, Seelze, Germany via Bangladesh Scientific Pvt. Ltd. Dhaka, Bangladesh. Standards of chlorpyrifos contained 99.3% purity and cypermethrin had 98% purity. Marketable sizes of brinjal, tomato, and cauliflower were collected from three different supervised field trials at 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 days after spray (DAS) which were sprayed with chlorpyrifos @ 3 mL per liter of water and cypermethrin @ 1 ml/L of water by knapsack sprayer. The formulated products of those were Dursban 20EC and Cymbush 10EC. The purity of formulated brand of both the insecticides was tested in the Pesticide Analytical Laboratory and found 100% pure. The sample extraction technique was used prescribed by William and George that was adopted with little modifications. Collected samples were chapped and grounded thoroughly with the meat grinder. A sub-sample of 20 g was taken into a wide mouth jar then 100 mL of hexane was added to it. Sodium Sulphate (Na₂SO₄) was also added with the sample until the water was removed from the sample. The mixture was then macerated with a high-speed homogenizer for 2 minutes. The homogenized material was then poured into a 250 mL conical flask and placed into the shaker for 12 hrs continuous shaking. After shaking, the slurry was filtered through a Buchner funnel with suction. The flask and filter cakes were rinsed with 25 mL of hexane each. The filtrate was then transferred into a 250 mL round bottom flask and was dried to 5 mL by evaporation using a rotary vacuum evaporator. The concentrated filtrate was then transferred into a 500 mL separatory funnel making 10 mL in volume. Around 20 mL methanol was added with 10 mL filtrate and shaked vigorously for 5 minutes. After shaking, the separatory funnel was set on a stand and kept undisturbed for 5 minutes. Then the clear part of the solution from the bottom of the separatory funnel was collected in a vial which was then centrifuged at 1200 rpm for 5 minutes. After centrifuge, the supernatant was collected for injection in Gas Chromatography. The concentrated extracts were subjected to analysis by GC-2010 (Shimadzu). Flame Thermionic Detector (FTD) was used for the detection of chlorpyrifos and the Electron Capture Detector (ECD) was used for the detection of cypermethrin. The capillary column used in FTD was ATTM-1, length 30m, Inner Diameter (ID) 0.25mm, and film thickness 0.25µm and in case of ECD it was Optima 1, and length, ID, and film thickness were the same. Nitrogen was used as a carrier and made up gas in ECD and in FTD it was Helium. Prior to the injection of the sample extract, standard solutions of different concentrations of both insecticides were prepared and injected with the above instrument parameters. The samples were calibrated against a four-pointed calibration curve of a standard solution of the concerned pesticide. Each peak was characterized by its retention time. Sample results were expressed in mg/kg automatically by the GC software which represented the concentration of the final volume injected. From this value, the actual amount of insecticide residue present in the sample was determined by using the following formula. Residue in sample (mg/kg) = Conc. obtained in injected volume (mg/kg) X Quantity of final volume (L)/Amount of sample taken (kg).

Source of Information: Asian Australas. J. Biosci. Biotechnol. 2021, 6 (2), 60-67

Article Link (Online Journal): doi: 10.3329/aajbb.v6i2.56141

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The degradation rate of cypermethrin was found faster in brinjal, tomato, and cauliflower and slower in all the analyzed vegetables for chlorpyrifos. So, cypermethrin might be the most suitable insecticide for the vegetables which would be harvested at the shortest period of time having a waiting period of 4 DAS in brinjal and tomato and 5 DAS in cauliflower but in the case of chlorpyrifos, vegetables could be harvested at 8 DAS in brinjal and tomato and 10 DAS in cauliflower. The findings of the study will help farmers, consumers, and other stakeholders to undertake a proper activity for the production of safe vegetables.

Knowledge Management: Journal