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Quantification of Residue Degradation of Dimethoate and Quinalphos in Major Vegetables Under Supervised Field Trial

M. S. Ahmed
Senior Scientific Officer
Entomology Division, BARI, Gazipur

M. A. Rahman
Senior Scientific Officer
Entomology Division, BARI, Gazipur

M. W. Akon
Senior Scientific Officer
Entomology Division, BARI, Gazipur

Afroza Begum
Scientific Officer
Entomology Division, BARI, Gazipur

Abstract/ Executive Summary:

The present study was undertaken to detect and quantify the left over residue of dimethoate in yard long bean, chilli, stem amaranth and red amaranth; quinalphos in brinjal, cabbage, red amaranth and stem amaranth and comparison between the detected residue levels with Maximum Residue Limit (MRL) set by FAO/WHO. Two supervised field trials (one for dimethoate and another for quinalphos) were carried out sprayed with the field dose (2 ml/L of water) of dimethoate and quinalphos. Samples were collected at 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 days after spray. The left over residue of dimethoate was detected up to 9 DAS in which MRL values (0.2 ppm) were found above up to 6 DAS with 0.227 ppm in yard long bean, 0.238 ppm in chilli, 0.219 ppm in stem amaranth and 0.206 ppm in red amaranth (at 7 DAS). Samples of 7 DAS and 8 DAS of dimethoate contained residues 0.023-0.059 ppm in yard long bean, 0.013-0.041 ppm in chilli, 0.018-0.057 ppm in stem amaranth and 0.029 ppm in red amaranth (at 8 DAS) which were below MRL. Quinalphos was detected up to 10 DAS.

Keywords: Quantification, Residue degradation, Dimethoate, Quinalphos, Vegetables

Location: Gazipur

Start Date: 10-10-2012

End Date: 05-05-2013

Program Area: Pest Management

Commodity:

Objectives:

1.To determine the rate of degradation of residue level of Dimethoate & Quinalphos in yard long bean, chilli, red amaranth, stem amaranth, brinjal and cabbage 2.To create database for PHI determination.

Methodology:

The standard for Dimethoate and Quinalphos contained 99.6% purity. Marketable size of cabbage, brinjal, yard long bean, chilli, stem amarenth and red amarenth were collected from two different supervised field trials at 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 days after spray (DAS) which were sprayed with Dimethoate and Quinalphos @ 2 ml/L of water. The purity of formulated insecticides were tested in the pesticide analytical laboratory and found to be 100% pure. Field collected samples (250g) were grounded thoroughly with the meat grinder. A sub sample of 20g was taken into a wide mouth jar then 100 ml of hexane was added to it. Sodium sulphate (Na2SO4) was also added with sample until water was removed from the sample. The mixture was then macerated with high-speed homogenizer for 2 minutes. The homogenized material was then poured into 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 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 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 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 and supernatant was collected for injection. The concentrated extracts were subjected to analysis for detection and quantification of pesticide residue in samples

Source of Information: Annual Report 2012-2013, Entomology Division, BARI , Gazipur

Article Link (Online Journal):

Funding Source:

1.	Budget: 2,00000.00

Total Budget (Tk.) : 2,00000.00

Achievement/Findings:

The left over residue of dimethoate was detected up to 9 DAS in which MRL values (0.2 ppm) were found above up to 6 DAS with 0.227 ppm in yard long bean, 0.238 ppm in chilli, 0.219 ppm in stem amaranth and 0.206 ppm in red amaranth (at 7 DAS). Samples of 7 DAS and 8 DAS of dimethoate contained residues 0.023-0.059 ppm in yard long bean, 0.013-0.041 ppm in chilli, 0.018-0.057 ppm in stem amaranth and 0.029 ppm in red amaranth (at 8 DAS) which were below MRL. Quinalphos was detected up to 10 DAS, of which up to 6 DAS the quantities of residue were above MRL in three vegetables (cabbage, red amaranth, stem amaranth) but in brinjal, the quantity of residue was above MRL at 7 DAS. This insecticide remained 0.043-0.094 ppm residue in cabbage, 0.041-0.099 ppm in red amaranth, 0.053-0.103 ppm in stem amaranth and 0.012-0.037 ppm in brinjal which were below MRL at 7 to 9 DAS. At 10 DAS, no residue was detected.

Knowledge Management: Report/Proceedings