Abstract
Disappearance of parathion and malathion residues in 9 different kinds of fruits and vegetables (pea, cucumber, lettuce, strawberry, black currant, apple, stringbean broccoli and spinach) sprayed about two weeks before the normal harvest was investigated. In addition, experiments were made on the effects of 3 different conserving processes upon the residues on black currant as well as on the persistence of the residues in conserves and frozen products during storage. The determination of parathion was carried out by a modification of the method of AVERELL and NORRIS, using a benzene-water-alcohol mixture and increased acidity in the reduction. The malathion was determined by the method of NORRIS et al. with the modification of benzene used as the extracting solvent instead of carbon tetrachloride. The procedures for the determination of total residues in plants are described in detail. The initial deposits of parathion varied from 0.49 to 14.60 ppm and those of malathion from less than 0.5 to 49.8 ppm, depending on the plant species. The half-life of the residues was 1—3 and 1—2 days, respectively. The most persistent residues were found in black currant; in these berries malathion could be determined qualitatively 28 days and parathion at least 43 days after spraying. Very small residues were found in the steam-juice prepared from black currants. In the preparation of two kinds of jam, 30 and 54 % of the parathion and 54 and 71 % of the malathion were destroyed. Both of the pesticides were very stable in black currant conserves as well as in frozen products for a period of at least 6 months.
Highlights
Since the use of pesticides, most of which are poisonous to humans, has rapidly increased in agriculture, especially in the past decade, it is of great importance from the standpoint of public health to investigate the occurrence of residues of these compounds in food products
The extraction of the pesticides was generally carried out within two hours after the collection of the samples. 0.5 kg of plant material was macerated in 350 ml of 94 % ethyl alcohol in a 1500 ml glass container for 1 min. in a Top Drive Macerator
In the method of Norris et at. (7) for the determination of malathion residues as well as in Conroy’s modification of this method (2), carbon tetrachloride is employed as the extracting solvent
Summary
The extraction of the pesticides was generally carried out within two hours after the collection of the samples. 0.5 kg of plant material was macerated in 350 ml of 94 % ethyl alcohol in a 1500 ml glass container for 1 min. in a Top Drive Macerator. 0.5 kg of plant material was macerated in 350 ml of 94 % ethyl alcohol in a 1500 ml glass container for 1 min. The macerator was rinsed with 150 ml of ethyl alcohol which was added to the macerated extract. 500 ml of benzene were added and the process of extraction was carried out for 1 hour on a drum-tumbler stripper (44 r.p.m.); during this time the benzene phase separated from the water-alcohol phase. Light & Co. Ltd., England) and 25 % anhydrous sodium sulphate (May & Baker Ltd., England). Ltd., England) and 25 % anhydrous sodium sulphate (May & Baker Ltd., England) Ten grams of this mixture were added to 250 ml of benzene extract and mixed for 5 min. The purified benzene was filtered and two samples of 100 ml were taken for the final parathion and malathion determinations
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