Icp qms

A method developed previously in our laboratory that was also accredited by the French Committee of Standardization (Cofrac) 19 was used for total As determination. 21 Briefly, 0.3 g of dry weight sample was precisely weighed in a quartz vessel and then thoroughly mixed with 3 mL of concentrated HNO 3 and 3 mL ultrapure water. The mixture was then submitted to microwave heating in a closed system during 7 min following the temperature program reported elsewhere. 21 After cooling at room temperature, the extract solutions were quantitatively transferred into 50 mL polyethylene flasks and then 100 µL of IS solution were added to achieve a final concentration of 2 µg L -1 of Sc; ultrapure water was finally added to the digested samples to a final volume of 50 mL. As t concentration in the digests was determined by ICP-QMS (Agilent) using an in-house validated method on the basis of the accuracy profile procedure. 22, 23 Briefly, the quantification was performed by external calibration (5 points) in the range 0-50 µg L -1 . The limit of quantification (LOQ) for As t determination was 0.002 mg kg -1 of fresh matter for a typical sample weight of 0.3 g and a final volume of 50 mL.