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International Journal of Environmental Research, Vol. 2, No. 1, 2008, pp.43-48 Solid phase extraction of pesticide residues in water samples: DDT and its metabolites Asi, M. R. , Hussain, A. and Muhmood, S. T.* Nuclear
Institute
for
Agriculture
and
Biology,
NIAB,
Faisalabad,
Pakistan Received 15 Jan. 2007; Revised 23 July 2007; Accepted 30 Aug 2007 Code Number: er08006 ABSTRACT Solid phase extraction (SPE) cartridge embedded with octadecyl C18 chain bounded to silica particles were used for the isolation and trace enrichment of pesticides from water samples collected from cotton, rice growing and municipal areas. The eluents were analyzed with high performance liquid chromatography (HPLC) using methanol (100%) as mobiles phase at different UV-Visible wavelengths. DDT and its metabolites were found in all areas but were not present in all samples. Concentration of pesticide residues varies from sample to sample and was in the range of 0.017-1.06 ng ml-1. Overall, recoveries ranged from 84%-91% for all target pesticides. Key words: SPE, HPLC, DDT, Metabolites INTRODUCTIONPesticides are widely used to control pests that affect agricultural crops and pests in homes, yards and gardens. These chemicals generally are manmade organic compounds. The principal processes that influence their potential for loss from soil to groundwater are volatilization (and subsequent diffusion), decomposition, retention by the soil, and transport by water. In some cases, pesticides used for plant protection may be applied to soil before planting, while for others, the application is made after seeding. Usually, most of the applied chemicals come into contact with soil. Application is by spraying a liquid, broadcasting granular formulation, or fumigation. Concern about environmental and health issue related to pest control makes it important to understand the possible hazards associated with their use and to minimize risks. Pesticides used on agricultural crops for control of weeds and insects can be migrated to surface water, local watersheds and ground water after application to crops or soil. Ground water pollution by agricultural chemicals has become growing concern in the world because 40-50 % of domestic drinking water is pumped from ground water resources. (Hallberg, 1989). Water pollution is the most damaging and has widespread environmental effecton agriculture productionand human health. The food contamination study in Pakistan conducted by National InstituteofHealth, Islamabad in 1984 revealed that organochlorine pesticide residues were the most frequently present in food. There had been widespread distribution of DDT and is metabolite as residues in food Tsipi, et al.,(1999). Chlorinated pesticides have also been found by Perveen and Masud (1988) in sample of milk, feed and cattle drinking water drawn from Karachi Cattle Colony. Hussain, et al., 1993, have also reported residues of DDT and its degrading products in human milk and adipose tissue samples in Faisalabad area. Therefore, it is great concern to determine the contamination level of ground and surface water for DDT and its metabolites, which are heavily sprayed in the past. Because of their widespread use, pesticides residues have been also found in drinking water (Kumari, etal., 1996), ground water (Plonke, et al., 1988 and Plonke and Glotfelty, 1989), surface water (Hinkley and Bidle, 1989 and Hussain, et al., 1997), and fog water (Glotfelty, et al., 1987). Insecticides utilized for cotton productions are intensive and can contribute to water quality problem (Crutchfield, et al., 1992). In the past, heavy use of organochlorine pesticide was practiced on field crops and malaria eradication program. Although the use of majority of them such as DDT and its metabolite have been banned but the long persistency of most of these has resulted in the continuing presence in the environment. However, these days some new less persistent pesticides such as organophosphorus are used for saving cotton from pests. But these compounds are highly toxic to aquatic organisms (Kendel 1999). As DDT is persistent (Gaeb, et al., 1975 and Billings and Bidleman, 1983) and was heavily sprayed, its residues may move from fields into ground water and pose health risk to ultimate users. They can reach surface water bodies in either dissolved or particulate form, which may impair the water quality and jeopardize the aquatic species. Concern about such adverse effects necessitates the present work for potential environmental impacts of the pesticides. MATERIALS & METHODSAgriculture is playing a pivot role in the economy of Pakistan. It has a very good water channel system in World to irrigate agriculture area. Maximum canals flow from Northern to Southern part of the country and irrigate vast area of agriculture farms. Maximum pesticides are used in the cotton, rice belt and vegetables to protect them. It is a great concern to check the water table, surface water and water supplies for pesticide contamination. Therefore, water samples were collected from different area of the country to analyze pesticides residues. The attention wasfocused to do sampling from tube-well; hand pump or well installed near heavily sprayed fields areas. The main purpose of sampling was to assess the present situation of pesticides levels in water. In order to assess possible impact of pesticides on aquatic ecosystem and drinking water supplies, water samples were taken from cotton, rice belts and municipal areas (Table 1). Water samples collected from different localities were processed for extraction and clean up for multi-residues analysis according to the procedure of Tanabe, et al., 2000. Solid phase extraction (SPE) was used for the clean up of the samples. Each sample was processed in triplicate to check reproducibility of results. 500 mL each filter water sample was passed through preconditioned SPE at a flow rate of 5 mL/min. After this cartridge was wash with 10 mL of distilled water then the cartridge was dried with air suction at a pressure of 80 mmHg for one hour. In order to check the dryness of pre-weight cartridge, they were weighed again. The target compounds collected on the cartridges were eluted successively with 3 mL acetone; 3 mL hexane and 3 mL ethyl acetate under reduce pressure. All these chemicals were redistilled by fraction distillation apparatus. The combined elutes were concentrated upto dryness under nitrogen stream and volume was adjusted to 1 mL with acetone. The pesticide residues analyses were carried out by using high performance liquid chromatograph (Shimadzu LC-10 AS) attached with Class 10 A software. The column used was SUPELCOSIL LC-18, 25 cm x 4.6 mm, 5 µL, Supelco, USA; pressure at isocratic system, 59 kg/cm2; flow rate, 0.5 mL/min; injection volume, 20 µL; oven temperature, 30 oC and methanol (100 %) HPLC grade was used in mobile phase. RESULTS & DISCUSSIONThe study involves the use of Solid Phase Extraction (SPE) cartridges for the extraction of organochlorine from water samples. The recoveries obtained for DDT and its various metabolites range between 84-91 % (Table 2). The overall recoveries for spiked level (2 ng/mL) in water for o, p/ -DDD, o, p/ -DDE, o,p/ -DDT, p, p/ -DDD, p, p/ -DDE, p, p/ -DDT were 85±5,89±8, 90±4, 91±6, 90±3, 87±11, respectively and are comparable with the results reported by Ambrus, et al., 1981. An excellent chromatographic separation of all the pesticides was obtained by using Reverse-Phase High Performance Liquid Chromatography (RP-HPLC). The controls were free of HPLC interference for the target compounds. HPLC analyses showed that o, p/ -DDT and p, p/ -DDTelute at a retention time of 7.956 and 7.557 min. respectively whereas o, p/ -DDE, o, p/ -DDD, p, p/ -DDE and p, p/ -DDD were 7.730, 6.975, 8.121, and 7.926 min. respectively. The limit of detection (LOD) for DDT analyses is in the range of 0.02-0.10 ng/ mL. The peaks observed for the standards (Fig. 1) and water samples were sharp and minimal tailing. Identification was made by comparing the peaks of samples with that of standards for qualitative and quantitative analysis. With the help of peak areas and retention times of standards, the concentrations of samples were calculated (Table 3). CONCLUSIONOrtho, para-DDD, o, p/ -DDE, o, p/ -DDT, p, p/ -DDE, p, p/ -DDT have been found in all the water samples except few locations where they were not present (Table 3). Para, para-DDD was not present in all the water samples collected from different places of the country. The concentration of o, p- DDD was highest (0.820 ng/mL) in hand pump, cotton belt area, Haroonabad. While lowest concentration (0.032 ng/mL) was found in hand pump, Ali town, Faisalabad. The higher concentration at Haroonabad may be due to the application of DDT in the past because in this area DDT was applied to control the pest against cotton or in malaria eradication program. All the other samples have the concentration in the range between 0.820 and 0.032 ng/mL. It was seen that Haroonabad canal water also contain higher (0.766 and 0.935 ng/mL) amount of o, p/ -DDE, and o, p/ -DDT, while lowest concentration (0.017 and 0.027 ng/mL) of these metabolites in hand pump, Sheikhopura, and NIAB canal water, Faisalabad. The lowest concentration is due to the non-use of DDT at these localities. The highest concentration (0.127 ng/mL) of p, p/ -DDE was found in tube water, Baidian, Lahore while its lower concentration was at NIAB canal water, Faisalabad. In Mianchannu, District Khanewal, highest concentration (1.06 ng/mL) of p, p/ -DDT was present i.e. 10 times more than the maximum admissible limits. Para, p/ -DDT was also present in nearly all localities except some where its concentration was lower i.e. below permissible limits. The concentration of detected pesticides, particularly in the cotton growing areas were certainly above the maximum admissible concentration of individual pesticide (0.1 ng/mL) set by European Community (David R Morgan, 1992). Generally, it was observed that DDT or its metabolites residues were under acceptable quantity in Municipal area like Lahore, Hyderabad while higher concentration were present in cotton growing belts particularly Bhawalpur, Khanewal etc. River Indus has higher concentration of DDT and its metabolites at the place of Kotari at the time of sampling. The occurrence of potentially hazardous chemicals such as DDT and its degrading products in crop growing areas/ground water/ drinking water, even in low concentration, is of real concern because of its potential for long term persistence and wide spread exposure to public. At the present time, only the agriculture land is affected, however, this may simply be a function of time when the other matrices will also contaminated. ACKNOWLEDGEMENTAuthors would like to thank to Dr. Charles S. Helling, Lead Scientist, USDA, Beltsville, MD, USA for gifting the Manifold SPE-10 and also grateful to IAEA for providing the reference standards. REFERENCES
Copyright 2008 - Graduate Faculty of Environment University of Tehran The following images related to this document are available:Photo images[er08006t2.jpg] [er08006f1.jpg] [er08006t3.jpg] [er08006t1.jpg] |
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