Atomic Absorption Determination of the Dissolved and Suspended Forms of Elements in Natural Water with Dynamic Sorption Preconcentration in Atomizers

Abstract

* Institute of Fundamental Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow oblast, Russia ** Department of Chemistry, Moscow State University, Vorob’evy gory, Moscow, 119899 Russia In natural water (river, sea, atmospheric, etc.) elements occur in dissolved and suspended forms. The data on the concentrations and ratio of these forms are important for geochemical and environmental studies. For the determination of ultralow concentrations of Ag, Bi, Cd, Pb, and Tl in dissolved (El diss ) and suspended (El susp ) forms and the total concentration (El diss + El susp ), we proposed a sorption–atomic-absorption method with the dynamic preconcentration of metals on the DETATA sorbent directly in a crucible electrothermal atomizer. A filtrate, unfiltered water sample, or solution obtained after the decomposition of a suspension (< 5– 50 mL) was pumped through a crucible microcolumn with holes of small diameter in the bottom and a graphite filter. The crucible microcolumn is a part (evaporation zone) of a two/three-chamber graphite electrothermal crucible–cell/crucible–cylinder–cell atomizer. The design of the atomizers provided independent programmed heating of the evaporation zone and the atomization zone for optimizing the processes and decreasing nonselective interferences and matrix effects. The cycle of the determination of elements in a solid matrix (concentrate, concentrate + suspension) commonly included drying, pyrolysis, and atomization ( 1800– 2600°e ) with the evaporation of elements to the isothermally heated zone. For the efficient suppression of interferences, we used the principles of element vapor filtration through graphite filters (between the evaporation and atomization zones) and fractional evaporation with the subsequent independent atomic-absorption analysis of the condensate.