TOWARDS STEADY-STATE DIRECT SOLID SAMPLE ANALYSIS BY INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY - QUALITATIVE EVALUATION OF ANINTRAPLASMIC POWDERED SAMPLE DIGESTER

A new type of reactor designed for continuous halogen-assisted digesti on and analysis of powdered samples was evaluated. Two different halog enating gas introduction methods were tested, as well as the use of an internal baffle to increase the residence time of the solids inside t he reactor. Studies were carried out on Al2O3 and CuO as model compoun ds for optimization of the reactor's parameters, such as the carrier g as flow, the fraction of halogenating gas and the feed rate, using Fre on-12 as the halogenating gas. A qualitative study of a pseudo fluidiz ed bed reactor (PFBR) was also performed on a soil sample certified re ference material (SO-4). The internal gas flow rate had to be kept to an absolute minimum in order to minimize cooling of the PFBR's inner w alls. pre-mixing of the halogenating reagent into the solid aerosol ca rrier resulted in a much more efficient reaction than separate flow in troduction. The use of a baffle drastically improved the digestion eff iciency by virtue of an increased solid residence time. The argon plas ma did not have a sufficiently high heat transfer capability to ensure proper operation of the PFBR under continuous sample loading. The por osity of the graphite used for the PFBR construction caused some taili ng and memory effects due to analyte seepage into the reactor's walls. (C) 1998 Elsevier Science B.V. All rights reserved.