A simplified method for the determination of forchlorfenuron in agricultural products by HPLC with UV detection was investigated. A chopped sample homogenate from agricultural products was extracted with acetone. The extract was filtrated and concentrated. The residues was loaded onto a Chem Elut column and extracted with ethyl acetate. The crude extract was purified on Oasis HLB and Bond Elut PSA mini-columns using a mixture of methanol and ethyl acetate. Forchlorfenuron was analyzed by HPLC with UV detection (263 nm). HPLC separation was performed on an ODS column with methanolῌwater as the mobile phase. Recoveries of forchlorfenuron from several agricultural products fortified at the level of 0.1 mg/g were in the range of 87.6ῌ99.5῍. The limit of detection (S/Nῌ3) was 0.005 mg/g in the sample.
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.
A simple analytical method was developed for the determination of total bromine in fruits and grain products by means of wavelength dispersive X-ray fluorescence spectrometry (WDXRF).Five gram samples of fresh fruits, frozen fruits, dried fruits and grain products were extracted with distilled water twice and diluted to 25 mL with distilled water. The sample solution (0.5 mL) was dripped onto the filter paper, which was dried and analyzed by WDXRF. The working curve was linear in the range of 0 to 10 mg/mL. Recoveries at the level of 5 mg/g were 76ῌ104̮. The detection limit was 0.5 mg/g and the determination limit was 1.5 mg/g in foods. Compared to the GC-ECD method, this method gave equivalent results for fresh fruits, frozen fruits and grain products. In addition, some dried fruits, in which a slightly high level was detected, gave almost the same results with the GC-ECD method. Therefore, this method is considered to be available as an alternative to the GC-ECD method.
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.
An analytical method for the determination of fluopicolide in livestock products and seafood was developed using LC-MS/MS. Sodium chloride was added to livestock products and seafood samples and fluopicolide was extracted twice with acetone after acidification with formic acid. The fat from the crude extract was removed using a macroporous diatomaceous earth column, followed by purification with a combination of mini-columns of GC graphite carbon and PSA ethylenediamine-N-propyl silylation silica gel . The average recovery n 5 of fluopicolide from 10 types of livestock products and seafood cattle fat, cattle liver, cattle muscle, chicken, eel, egg, freshwater clam, honey, milk and salmon spiked at the MRLs or at the uniform limit 0.01 ppm was 96-100 , with a relative standard deviation of 2.3-6.2 . The limit of quantitation of the developed method was calculated to be 0.01 mg/kg.
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