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Determination of Residue Level of Endosulfan in Black Tea in Bangladesh

M. Ahmed
Chief Scientific Officer
Bangladesh Tea Research Institute, Srimangal, Moulavibazar.

M. S. A. Mamun
Scientific Officer
Bangladesh Tea Research Institute, Srimangal, Moulavibazar, Bangladesh

A. Biswas
Scientific Officer
Bangladesh Tea Research Institute, Srimangal, Moulavibazar, Bangladesh

S. K. Paul
Scientific Officer
Bangladesh Tea Research Institute, Srimangal, Moulavibazar, Bangladesh

Abstract/ Executive Summary:

The study was conducted at Bangladesh Tea Research Institute, Srimangal, Moulavibazar, Bangladesh during 2007-08 in both wet and dry season on the mature tea to determine the residue level of Endosulfan (Thiodan 35EC) in black tea at different plucking intervals after spraying and their degradation rate in order to fix the plucking interval to keep the residue level at Maximum Residue Limit (MRL) or below. Two doses of Endosulfan i.e. normal (1.5 Lha^-1) and double (3.0 Lha^-1) were applied. In dry season, the initial deposits of residues were 129 and 183 ppm on 0 day and declined to 0.91 and 2.11 ppm on the 14^th day whereas in wet season, the initial residues were 122 and 171 ppm on 0 day and declined to 0.87 and 2.01 ppm on the 14^th day at normal and double doses respectively. The dissipating rate of residues of Endosulfan with the increase of plucking days was not uniform, rather it was expotential. Residue levels of Endosulfan at the commonly followed Pre Harvest Interval (PHI) i.e 7^th day were 1.68 and 3.14 ppm in normal and double doses respectively in the dry season while in the wet season the residue levels were recorded as 1.40 and 2.93 ppm. This slight variation in result at the same PHI indicates that seasonal variation has a role on the level of residues. However, these seasonal variation as well as dose rate differences were statistically non significant within themselves. Commonly followed PHI (7^th day), the samples of Endosulfan at normal dose in both seasons did not exceed the MRLs imposed by EPA, Codex Commission, EEC/EU and German law.

Keywords: Residue, Endosulfan , Black tea

Location: Bangladesh Tea Research Institute, Srimangal, Moulavibazar.

Start Date: 01-10-2007

End Date: 31-05-2008

Program Area: Crop-Soil-Water Management

Commodity: Tea

Objectives:

1. To find out the residue level of Endosulfan in black tea at different plucking intervals after spraying;

2. To fix a correct and acceptable plucking round after application of Endosulfan in order to keep the residue at MRL or below.

Methodology:

Experiments on Endosulfan were carried out on the mature tea at the main farm of Bangladesh Tea Research Institute, Srimangal, Moulavibazar, Bangladesh as per the GAP protocol in both dry (October 2007) and wet season (May 2008). The mean minimum temperature, mean miximum temperature, humidit and rainfall during the experiment period at Srimangal were 19.7⁰C, 30.7⁰C, 80% and 2375 mm respectively (Anonymous, 2008b). The experimental area was divided into 42 equal plots for 3 replications of both the insecticidal doses. Untreated control treatment was also considered for the comparison of the insecticidal doses. Endosulfan (Thiodan 35EC) was applied in all the plots at approved doses i.e. 1.5 (normal) and 3.0 (double) Lha^-1in 500 liter of water against Tea mosquito bug on the mature tea (Ahmed and Shahiduzzaman, 2007). According to FAO guidelines (Anonymous, 2002a), the samples of tea shoots were harvested at ‘0’ day, 1^st day, 3^rd, 5^th, 7^th, 10^th & 14^th day after application where 0 day sample was collected after 4 hours of insecticide application. Leaves were plucked at respective interval and were processed in the Mini Tea Factory of the Institute following Crushing, Tearing and Curling (CTC) method. The triple action of Crushing, Tearing and Curling done by the CTC machine is the result of the work of two contra rotating toothed stainless steel rollers. The size and profile of the tooth and the differential speed of the rollers are important in bringing about the desired cut. The CTC cut determines the leaf appearance, grade percentages, liquor and the infusion of the tea. For blank sample, leaves from the plots were collected before spraying and manufactured in the Mini Tea Factory adopting the same method. Manufactured leaves (black tea) were then grinded by coffee grinder and hydrated. Subsequent extraction and clean up were carried out according to the methods developed by Ahmed & Sarker (2002) at Central Science Laboratory, UK. Determination was done by Electron Captured Detector using Shimadzu Gas Chromatograph (GC-14B) with DB-5 capillary column (0.53 mm i.d) and Nitrogen (99.997% purity) as carrier gas. Hexane and Acetone were used as extracting reagent and Florisil as clean-up reagent.

Source of Information: SAARC JOURNAL OF AGRICULTURE, Vol. 7, Issue 1, 2009, pp. 56-62, ISSN 1682-8348, SAARC Agricultural Information Centre.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Tea being an export oriented commodity, all the required measure must be taken to keep the residues well below the Maximum Residue Limit (MRL) to overcome the non-tariff trade barriers under WTO regimes. Other parameters on the level of residues like No-observed-Adverse Effect Level (NOAEL), Acceptable Daily Intake (ADI), Food Factor and Maximum Permissible Intake (MPI) should be taken into considerable according to FAO guidelines. With these parameters, the MRL and PHI (Pre-harvest Interval) can be strictly followed for acceptable the world market. As such, scientific approach towards its practical and routine application for the benefit of tea industry will need consistency. Only BTRI recommended Endosulfan with approved dose should be applied when it is absolutely essential. Seven day period is the safe harvest interval after spraying of Endosulfan.

Knowledge Management: Journal