Determination of tellurium at ultratrace levels by on-line solid phase microextraction coupled to GFAAS

J. PEDRO; J. STRIPEIKIS; A. BONIVARDI; M. TUDINO

Barquisimeto, Venezuela

Simposio; 9th, Rio Symposium on Atomic Spectrometry; 2006

Facultad Experimental de Ciencias, Univ. Zulia, Venezuela e Instituto de Química; Universidad Federal de Bahia, BA. Brazil

On-line coupling of flow injection pre-concentration manifolds to high performance detectors such as graphite furnaces allows to extend the detection capability of this technique up to the ultratrace level (below ng.ml-1). Solid phase extraction in packed micro-columns and precipitation or co-precipitation of the analyte followed by collection onto adsorbent resins or knotted reactors are the more popular strategies for  pre-concentration purposes. These approaches require a careful optimization of the variables affecting the performance of the analytical methodology such as: the design of the flow injection manifold including the geometry and location of the micro-column and the characteristics of the filling, the eluant, the flow rate and pH of retention and elution, the heating program, the matrix modification and the coupling between the flow system and the atomizer. Since the optimization of the instrumental parameters and the graphite furnace heating program for Te determination were reported in a previous study[1], in this work we present two systems for the on-line pre-concentration of tellurium in tap water. The first system involves strong anionic resins (Dowex X8) as micro-column packaging and the second is based on co-precipitation of the analyte with La(OH)3  followed by retention onto adsorbent fillings (XAD resins) or knotted reactors. Both systems (optimized by means of a Box-Behnken experimental design) will be compared in terms of limit of detection, linear range, RSD%, sample throughput, micro-columns lifetime, easiness of operation, aptitude for a successful coupling flow system-discrete analyzer, etc. The applications to the determination of tellurium in tap water will be shown as well as the validation of the analytical methodology employing SRM 1643e as certified reference material.   [1] Termal stabilization of tellurium in mineral acid solutions: Use of permanent  modifiers for its determination in sulfur by GFAAS. J. Pedro, J. Stripeikis, A. Bonivardi & M. Tudino. Talanta, 69(1), 199-203 (2006).