Highly sensitive pneumatic nebulization flame furnace atomic absorption spectrometry: complete sample aerosol introduction and on-line preconcentration of cadmium by atom trap

摘要

Complete introduction of sample aerosol into flame AAS is achieved by hyphenating pneumatic nebulization (PN) with flame furnace AAS (FF-AAS). The analyte solution is introduced via a pneumatic nebulizer into the flame heated furnace by a flow of carrier gas (air or argon). The middle part of the flame furnace, where the carrier gas impacts, is cooled by the gas flow as well as the sample aerosol, and this provides a fine strategy for on-line atom trapping for the purpose of preconcentration. A stainless steel plate is put on the top of the flame burner in the middle to form a flame-free zone, which also lowers the temperature of the flame furnace and facilitates the atom trapping process. Cadmium is selected as the analyte element because its low temperature atomization characteristic most suits for this approach. With 10 s preconcentration time (corresponding to 300 μL sample solution), a sensitivity enhancement factor of 730 (over conventional flame AAS) is obtained. The limit of detection for cadmium by the proposed method was found to be 15 ng L~(-1), comparable to that by graphite furnace AAS or chemical vapour generation atomic fluorescence spectrometry. This superior detectability originates from the atom trapping step involved in this simple and cost-effective approach.