Plasma parameter and film casting optimization for the determination of particulate matter in a sol–gel matrix by radiofrequency glow discharge optical emission spectrometry (rf-GD-OES)

Abstract

Solids analysis has typically suffered from the lack of true analytical blanks and the inability to study particulate solids in their native state. Reported here is an approach to the analysis of particulate matter entrapped in a sol–gel matrix by radiofrequency glow discharge optical emission spectroscopy (rf-GD-OES). Sol–gel glasses are synthesized by acid-catalyzed condensation of methyltrimethoxysilane (MTMOS) and spun cast onto glass substrates. Slurries of powdered NIST standard reference materials (SRMs) 1884a Portland Cement and 1648 Urban Particulate Matter were incorporated into the films and analyzed for both main and trace element components. Cast films were analyzed to determine the discharge operating conditions and effects of particle size and deposited layer thickness while monitoring optical emission lines of a number of analytes. Using the sol–gel method, analytical blanks were obtained by use of an undoped sol–gel. Detection limits were determined for minor elements using background/blank subtraction and were found to be in the range of 1–12 μg g⁻¹ in Portland Cement for elements Al, Ca, P, Mn and Fe, which corresponds to single-nanogram absolute detection limits.