|Keywords (Extracted from title, table of contents and abstract of thesis)
solid-phase extraction, chromatographic determination, pesticides, pest, mancozeb, triforin, thiophanate-methyl, fenarimol, carbendazim, endosulfan, ddt, heptachlor, endosulfan
Modern agriculture has and is producing thousand of tonnes of food for domestic and foreign market. The tool of the trade includes many different chemical compounds that are used for a wide variety of pest problems. Pesticide use has improved both the efficiency of growing crops and the quality of food produced. However, alongwith the benefits emerged the potential effect of trace amounts of pesticide residues remaining on food commodities and there has been great concern by consumer groups demanding assurance from the agriculture community that the food we eat is indeed safe. The use of contaminated fruits and vegetables for long time may cause illness and other serious diseases in man and wild lives. Different analytical tools like solid-phase extraction (SPE), thin layer chromatography (TLC), gas chromatography (GC) and high performance liquid chromatography (HPLC) were used to assess the pesticide residue level in water, fruits and vegetable samples.
Ethyl acetate, acetone and methanol proved to be good solvents for successive elution of pesticides adsorbed on the cartridge bed. The recovery percentage of each pesticide recovered from SPE cartridge (ENVI-Carb) showed excellent behaviour (>95%). From the results it is revealed that 200 ml sample volume and 2 minutes equilibrium time before the elution of pesticides gave high recovery of every type of pesticide. Waters of different aquifers behaved in the same way but that water, which had soil particles, showed some adsorption of pesticide which could not be eluted completely. SPE cartridges were used but ENVI-Carb found good among others with salient features for the pre-concentration of pesticide residues from surface and ground waters. It showed consistent recovery behaviour after successive elution with organic solvents and did not develop any backpressure. The use of this technology for the extraction and preconcentration of pesticide residues for aquifer samples did not pose any risk to the environment due to the less use of solvent. The extracted/eluted water samples by SPE cartridges were analyzed by GC and HPLC.
The water samples from cotton-belt contained maximum pesticide residues as compared to rice and vegetable areas. Well water was found highly contaminated than canal and handpump waters whereas least residues were found in tubewell samples. High residues of endosulfan were found in aquifers of cotton-belt area. Residues of insecticides were found in greater proportion than the herbicides and fungicides in water samples. No fungicide was detected in water samples of cotton area but chlorothalonil was detected in surface water of Gujranwala, surface and ground waters of Sialkot and Sheikhupura but no residue was detected in Faisalabad areas. Water samples of vegetable areas were analyzed and it was found that alpha-endosulfan, lindane and p, p/-DDT were present in all samples except tubewell water. Alpha-endosulfan was in high concentrations in water samples following lindane and p, p/-DDT. Most water samples were found contaminated with fungicides and their concentrations in canal water samples were not same in the three provinces. The concentration of isoproturon was higher in NWFP water samples as compared to Punjab and Sindh. Methamidophos, monocrotophos and phosphamidon residues were found higher in canal water in Punjab, Sindh and NWFP but these compounds have lower residues in tubewell waters in these provinces.
Pesticide residues in vegetables and fruits were determined by GC, HPLC and HPTLC. High residue of mancozeb was detected in tomato and potato. A very high concentration of carbendazim was found in cauliflower, tomato and potato samples belonging to farm areas. Benomyl was detected in ladyfinger, bittergourd, brinjal and pumpkin whereas chlorothalonil was found only in bittergourd and brinjal. Imidacloprid was detected in most vegetable samples but high concentration was found in tomato. Chlorpyriphos and methamidophos were also found in most vegetables but high residues of chlorpyriphos and methamidophos were detected in cauliflower, spinach, tomato, potato and ladyfinger respectively. Pyrethroids were also found in all vegetable samples but their residues were higher in farm samples as compared to city area samples. High residues of bifenthrin were found in spinach, cauliflower, tomato, ladyfinger and green peas whereas cypermethrin and cyhalothrin were detected in brinjal and green peas. Decamethrin was only found in potato. Endosulfan, heptachlor and DDT were also found in most vegetables.
Mancozeb, triforin, thiophanate-methyl, fenarimol and carbendazim were detected in most fruits and higher concentrations of these compounds were detected in farm samples. High residue of carbendazim was found in apricot samples. Endosulfan, DDT and heptachlor were also found in fruit samples. Melon had high residues of endosulfan and DDT than other fruits whereas no residues of endosulfan and DDT were detected in guava and apple samples. Heptachlor was also found in pear, banana, plum, apricot and grapes in substantial concentrations. High residues of cypermethrin, bifenthrin, fenvalerate, cyhalothrin and fenpropathrin were found in pear, orange, banana, plum, apricot, melon, guava, mango and apple samples. Imidacloprid was only found in pear, orange and banana whereas dimethoate and monocrotophos in apple and mango samples.