دانلود رایگان مقاله لاتین بقایای آفت کش آلی کلر در نمونه خام مواد غذایی بازارهای باز از سایت الزویر
عنوان فارسی مقاله:
ارزیابی بقایای آفت کش های آلی کلر در نمونه های خام مواد غذایی بازارهای باز در دو شهر آفریقایی
عنوان انگلیسی مقاله:
Assessment of organochlorine pesticide residues in raw food samples from open markets in two African cities
کد محصول : E5094
بخشی از مقاله انگلیسی:
2. Materials and methods
2.1. Materials and reagents A mixture of seventeen analytical grade organochlorine pesticides constituted of a e BHC, b eBHC, ge BHC, d e BHC, heptachlor, heptachlor epoxide, aldrin,, endrin, endrin aldehyde, dieldrin, endosulfan I, endosulfan II, endosulfan sulphate, 4,40 - DDT, 4,40 e DDD, 4,40 e DDE and methoxychlor were purchased from SigmaeAldrich, South Africa. The purity of the standard was 95%. The stock solutions of 5 mg L1 were prepared in hexane/toluene (50/ 50) mixture and stored in freezer at 4 C. The working solutions of different concentrations were prepared daily by dilution of the stock solution with the same solvent mixture. The concentration of 1, 5 and 10 mg L1 were used as working solution for calibration Hexane and toluene used was of analytical grade from Merck (Johannesburg South Africa). Acetonitrile, magnesium sulphate monohydrate, sodium chloride and bondesil primary/secondary amine (PSA) were from SigmaeAldrich (Johannesburg South Africa). Anhydrous sodium sulphate was from Merck (Johannesburg, South Africa). The analysis was carried out by GC 7890A (Agilent Technologies, DE, USA) equipped with flame ionization detector (FID) and electron capture detector (ECD) and GCxGC/TOFMS, 7890B (LECO Corp., St Joseph, MI, USA) with a 7683 series injector (Agilent Technologies, DE, USA). 2.2. Sampling 120 food samples constituted of beans, cabbage, beef and fish (tilapia) were purchased in Kinshasa (60 samples) and Johannesburg (60 samples) open markets from July till October 2015. In Kinshasa, the food samples were purchased in the biggest urban open market. In this market, foods are sold on the floor without any hygienic condition and in some areas near the high traffic road. All the food samples were kept in closed polypropylene plastic boxes in refrigerator (- 4 C) at the University of Kinshasa before being send by courier to South Africa. In Johannesburg, the food samples were purchased in Johannesburg town market from individual vendors. Concerning the vegetables (cabbage, beans) and beef, the sources were not clari- fied. The tilapia fish bought were from Mpumalanga province. All the food samples were kept in closed polypropylene plastic boxes in refrigerator (- 4 C) at the University of the Witwatersrand, Johannesburg. 2.3. QuEChERS extraction method The QuEChERS extraction method was done using the modified procedure reported by Rawn et al. (2010). Homogenized samples with no pesticides detected on previous occasions were used for recovery studies, and for the preparation of matrix-matched standards for calibration. The homogenised samples were spiked with 1, 5 and 10 mg L1 of a standard mixture of seventeen organochlorines. The spiked samples were allowed to stand for 30 min. Ten grams of homogenized food sample was put in a 50 ml Teflon tube. Then 10 ml of acetonitrile was added and the sample was shaken strongly for 1 min. This was followed by salting-out step with additions 1.5 g sodium chloride and 3 g of anhydrous magnesium sulphate into the tube and the mixture was shaken vigorously for 1 min and then centrifuged. After centrifuge, 6.5 ml of organic supernatant was transferred into the polypropylene centrifuge tube to clean-up with 1.65 g anhydrous magnesium sulphate and 27.5 g primary/secondary amine (PSA). The solution was centrifuged for 5 min and filtered using a 0.45 mm PTFE and injected in the GC eECD and/or GCxGC/TOFMS for analysis. The GCxGC/TOFMS was used to confirm the identification of compounds in samples. 2
کلمات کلیدی:
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