On-Line Preconcentration of Zinc on Ethyl Vinyl Acetate prior to its Determination by Vapor Generation Associated to Inductively Coupled Plasma Optical Emission Spectrometry

LUIS A. ESCUDERO; S. CERUTTI; LUIS D. MARTÍNEZ; J.A. SALONIA; J. A. GASQUEZ

Mar del Plata

Simposio; 11th Rio Symposium on atomic spectrometry; 2010

The chemical vapor generation (CVG) technique has been used in analytical chemistry because the generation of gaseous analytes and their introduction into atomization cells can offer several significant advantages over conventional pneumatic nebulization methods, which include separation of the analyte from the undesirable matrix components that leads to improved selectivity in many instances, analyte transport efficiency, elimination of the need for a nebulizer, and-in many cases- more efficient analyte atomization [1, 2]. The application of CVG has been limited to the classical group of elements such as Hg, As, Sb, Bi, Se, Te, Ge, Sn, and Pb. In recent years, use of hydride generation techniques has expanded in scope to encompass the generation of  “unconventional” volatile species (possibly as hydrides, vapors, or other unidentified species) of different noble and transition metals and noble metals and noticeable efforts have been dedicated to clarification of mechanistic aspects [3-5]. More attention has been paid to the development of vapor generation of zinc because this element plays an important role in environment and human health [6, 7]. Considering the low content of zinc in these samples, sensitive analytical techniques are required to obtain low detection limits (DLs). However, the DLs of some atomic spectroscopic techniques, such as inductively coupled plasma optical emission spectrometry (ICP-OES), are not always compatible with the low levels of Zn in environmental samples. Preconcentration is an effective means of extending the DLs of the ICP-OES technique. In the present work, for first time, an on-line preconcentration procedure has been coupled to zinc vapor generation. The variables involving the preconcentration and the vapor generation were optimized using full factorial designs, respectively. Trace amounts of zinc were preconcentrated by sorption on a minicolumn packed with ethyl vinyl acetate. The analyte retained was removed from the minicolumn with hydrochloric acid. After that, volatile species of zinc were generated by merging the acidified eluent and sodium tetrahydroborate (III) in a continuous flow system. The gaseous analyte was subsequently introduced via a stream of Ar carrier into the inlet tube of the inductively coupled plasma torch. An enhancement factor of 58-fold for a sample volume of 25 ml was obtained. The detection limit achieved was 0.06 mg L-1. Potential interfering effects on the Zn signal were examined. The proposed method was successfully applied to the determination of traces of Zn in a certified reference material (VKI QC Metal LL1 DHI (Water & Environment) Denmark) and water samples.