Method performance of the closed vessel microwave-assisted acid extractionusing 50% HNO3 : HCl (3 : 2) with positive pressure Teflon membrane filtration

The recovery from soil of 22 metals on the U.S. Environmental Protection Ag ency's (EPA) Target inorganic analyte list is described. The extraction met hod was developed to provide a safe, rapid, and analytically reliable means of leaching metals from soils and sediments in one procedure. The influenc e of digestion matrices, filtration media, reference standard types and ins trument performance of inductively coupled plasma/optical emission spectros copy is presented. The method employs a closed vessel, temperature and pres sure controlled, microwave acid digestion using 20 mt of 50% HNO3:HCl in a ratio of (3:2). The digestate was filtered through a positive pressure Tefl on membrane cartridge. This procedure recovered all metals at concentration s equal to or greater than what is possible by EPA standardized methods or other methods published in the literature. Excellent method precision and a ccuracy was obtained for all metals, especially Ag and Sb. Results show tha t the positive Teflon membrane filtration system yielded higher and statist ically different concentrations of Mn, Zn, Cu, Fe. As, Cd, Pbt Ag, and Sb t han paper filtration in half the time. These findings were produced from st andard reference soils and soil collected from a hazardous waste site landf ill.