Rapid determination of inorganic elements in airborne particulate matter by using acidified subcritical-water extraction and inductively-coupled plasma–optical-emission spectrometry

Abstract

A rapid and simple method has been developed for determination of inorganic elements in airborne particulate matter (PM10) by using acidified subcritical water and ICP–OES. Elements such as Al, As, B, Ba, Cd, Cu, Fe, Mn, Pb, Se, and Zn were rapidly and efficiently extracted from PM10 samples with a solution of 0.1 mol L⁻¹ HNO₃ under subcritical conditions. The method requires approximately 5% of the amount of acid used in the standard microwave extraction procedure. The material selected for the subcritical extraction manifold was poly ether ether ketone (PEEK), to avoid sample contamination with elements present in previously reported stainless-steel manifolds. The extraction temperature, time of static and dynamic extraction, and flow rate of acidified water were studied keeping the pressure controlled at about 1,500 psig. The efficiency of extraction of most of the analytes increased with temperature, tending to quantitative extraction at temperatures near 150°C. After the extraction process the analytes were determined directly in the extract by ICP–OES. When the method was compared with the USEPA counterpart, the results indicate that under optimized conditions (static extraction time: 15 min, dynamic extraction time: 30 min, flow rate: 2 mL min⁻¹) the analytes were extracted with recoveries between 73 and 158%. Alternatively, by using an extraction time of 15 min, the method could be used to screen for all the elements, with recoveries over 50%. The developed method was applied to the determination of inorganic elements in airborne particulate matter in the atmosphere of Santiago, Chile.