An analytical method for the determination of 32 kinds of pesticide residues in onions, Welsh onions and mushrooms using gas chromatograph with an atomic emission detector (GC-AED) was developed. The pesticides were extracted with acetone῍n-hexane (2 : 3) mixture῍ The crude extract was partitioned between 5ΐ sodium chloride and ethyl acetate῍n-hexane (1 : 4) mixture. The extract was passed through a Florisil ῌ mini-column for cleanup with 10 mL of acetone῍ n-hexane (1 : 9) mixture. Although the sensitivity of GC-AED was inferior to that of GC-ECD, GC-AED has a superior element-selectivity. Therefore pesticide residues in foods could be analyzed more exactly by using GC-AED. Thirty-two pesticides including chlorine in onion, Welsh onion and shiitake mushroom were detected without interference. Recoveries of these pesticides from samples determined by GC-AED were 64῍114ΐ, except for a few pesticides.
Four unknown peaks were detected in GC chromatograms during analysis of organophosphorus pesticide residues in foods. They were identified by using GC/MS as triethyl phosphate (TEP), tributyl phosphate (TBP), diphenyl 2-ethylhexyl phosphate (DPEHP) and N-ethyltoluenesulfoneamide (NETSA), which are used as plasticizers or flame retardants in food packaging. These chemical substances were detected in the range of tr. (below 0.01 microg/g) to 11 micro/g from 29 samples, and they were also detected in the packaging. It was supposed that they were transferred to the foods from the packaging. Furthermore, they were detected in some cereals and cereal products which contain fat and had been preserved for a long time.
A survey of pesticide residues in 595 imported frozen products on the Tokyo market from April 1989 to March 2008 was carried out. Forty three kinds of pesticides, including organophosphorus, organochlorine, carbamate, pyrethroid and others, were detected between levels of trace (below 0.01 ppm) and 4.6 ppm from 162 samples. Chlorpyrifos, cypermethrin and omethoate were frequently detected in green vegetables (komatsuna leaf and spinach), cypermethrin and methamidophos were detected in pods and seeds (green soybean and string pea), chlorpropham (CIPC) was detected in potato, and captan and carbaryl were detected in berries (blueberry, raspberry and strawberry). The hydrophilic pesticide methamidophos was detected in flesh of lychee. Residue levels of these pesticides were calculated as between less than 0.5̮ and 30̮ of their ADI values according to the daily intake of frozen products. Therefore, these frozen products should be safe when they were eaten in customary amounts.
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