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

The recovery from soil of 22 metals on the U.S. Environmental Protection Agency’s (EPA) Target inorganic analyte list is described. The extraction method was developed to provide a safe, rapid, and analytically reliable means of leaching metals from soils and sediments in one procedure. The influence of digestion matrices, filtration media, reference standard types and instrument performance of inductively coupled plasma/optical emission spectroscopy is presented. The method employs a closed vessel, temperature and pressure controlled, microwave acid digestion using 20 mL of 50% HNO₃ : HCl in a ratio of (3 : 2). The digestate was filtered through a positive pressure Teflon membrane cartridge. This procedure recovered all metals at concentrations equal to or greater than what is possible by EPA standardized methods or other methods published in the literature. Excellent method precision and accuracy was obtained for all metals, especially Ag and Sb. Results show that the positive Teflon membrane filtration system yielded higher and statistically different concentrations of Mn, Zn, Cu, Fe, As, Cd, Pb, Ag, and Sb than paper filtration in half the time. These findings were produced from standard reference soils and soil collected from a hazardous waste site landfill. Received: 6 August 1998 / Revised: 14 January 1999 / Accepted: 19 January 1999     

Nontargeted Screening Using Gas Chromatography–Atmospheric Pressure Ionization Mass Spectrometry: Recent Trends and Emerging Potential

Gas chromatography–high-resolution mass spectrometry (GC–HRMS) is a powerful nontargeted screening technique that promises to accelerate the identification of environmental pollutants. Currently, most GC–HRMS instruments are equipped with electron ionization (EI), but atmospheric pressure ionization (API) ion sources have attracted renewed interest because: (i) collisional cooling at atmospheric pressure minimizes fragmentation, resulting in an increased yield of molecular ions for elemental composition determination and improved detection limits; (ii) a wide range of sophisticated tandem (ion mobility) mass spectrometers can be easily adapted for operation with GC–API; and (iii) the conditions of an atmospheric pressure ion source can promote structure diagnostic ion–molecule reactions that are otherwise difficult to perform using conventional GC–MS instrumentation. This literature review addresses the merits of GC–API for nontargeted screening while summarizing recent applications using various GC–API techniques. One perceived drawback of GC–API is the paucity of spectral libraries that can be used to guide structure elucidation. Herein, novel data acquisition, deconvolution and spectral prediction tools will be reviewed. With continued development, it is anticipated that API may eventually supplant EI as the de facto GC–MS ion source used to identify unknowns.