Matrix Effects Studies with Fused-Silica Aperture Thermospray Sample Introduction to ICP-AES

Abstract

Matrix effects with fused-silica aperture thermospray (FSApT) sample introduction for ICP-AES are found to be higher than those for pneumatic sample introduction. The effects are comparable to those reported for sample introduction to ICP-AES using ultrasonic nebulization with desolvation. The matrix effects for >mg/mL levels of Ca are found to be influenced by the thermospray operating temperature. By the use of higher thermospray temperatures, matrix effects due to transport losses are reduced to low levels, presumably by reduction of primary aerosol particle sizes. Background increases due to higher Ca input with the thermospray system result in small changes in background noise that do not appear to have a large effect on limits of detection (LODs). Matrix effects occurring within the plasma appear to be the primary source of interferences. Ca interferences can also be reduced or eliminated by appropriate adjustment of the aerosol carrier gas flow rate. For simultaneous multielement analysis, a compromise flow rate must be chosen. With the use of such compromise conditions, LODs for a wide range of elements were increased in the presence of Ca, but were on average within a factor of 1.7 of those obtained in the absence of Ca. LODs obtained for analytes in the presence of 1000–3000 μg/mL Ca for FSApT/ICP-AES were all below United States Environmental Protection Agency (EPA) required limits for Toxicity Characteristic Leaching Procedure (TCLP) samples derived from concrete stabilized hazardous waste, while pneumatic sample introduction provided inadequate detection for half the key elements tested.