2.2.2. Extraction and clean up A modified version of the QuEChERS method was applied to
obtain pesticide extracts. The QuEChERS Restek Q-Sep salt kits were used in the extraction process and the Restek dSPE Q-Sep adsorbent kits were employed in the clean-up procedure. In a centrifuge tube, 10 g of previously homogenized sample were weighed, 15 ml of solvent were poured into it and then it was manually shaken by one minute. The extraction solvent consisted of acetonitrile and acetic acid 1% (v/v). Thereafter, 6 g of anhydrous MgSO
and 1 g of sodium acetate were added, and it was shaken again. The tube was centrifuged at 4500 rpm for 5 min and 10 ml of the supernatant (solution A) were measured using a pipette and then transferred to a 15 ml centrifuge tube. In the case of the cleanup procedure, 25 mg of PSA (primary/secondary amine) and 150 mg of anhydrous MgSO
4
were added for each extract milliliter of solution A. Afterwards, it was shaken by 30 s and centrifuged by 2 min at 4500 rpm. Finally, the supernatant was filtered through a 0.22 mm PTFE filter (Ahumada & Zamudio, 2011a).
4
2.2.2. Extraction and clean up A modified version of the QuEChERS method was applied toobtain pesticide extracts. The QuEChERS Restek Q-Sep salt kits were used in the extraction process and the Restek dSPE Q-Sep adsorbent kits were employed in the clean-up procedure. In a centrifuge tube, 10 g of previously homogenized sample were weighed, 15 ml of solvent were poured into it and then it was manually shaken by one minute. The extraction solvent consisted of acetonitrile and acetic acid 1% (v/v). Thereafter, 6 g of anhydrous MgSOand 1 g of sodium acetate were added, and it was shaken again. The tube was centrifuged at 4500 rpm for 5 min and 10 ml of the supernatant (solution A) were measured using a pipette and then transferred to a 15 ml centrifuge tube. In the case of the cleanup procedure, 25 mg of PSA (primary/secondary amine) and 150 mg of anhydrous MgSO4were added for each extract milliliter of solution A. Afterwards, it was shaken by 30 s and centrifuged by 2 min at 4500 rpm. Finally, the supernatant was filtered through a 0.22 mm PTFE filter (Ahumada & Zamudio, 2011a).4
การแปล กรุณารอสักครู่..
