Tellurium Speciation Using Hydride Generation Atomic Absorption Spectrometry And In-situ Graphite Cuvette Trapping

Autor: Yildirim, Emrah
Jazyk: angličtina
Rok vydání: 2009
Předmět:
Druh dokumentu: M.S. Thesis
Popis: In recent years speciation analysis is becoming more important as it is known that each chemical form of an element behaves differently in biological and environmental media. Since abundance of tellurium in earth crust is extremely low, very sensitive and accurate methods are needed to determine the concentration of tellurium. Hydride generation atomic absorption is a sensitive, fast and economical technique applied for the determination of tellurium. Speciation of tellurium can be achieved by making use of different kinetic behaviors of Te(IV) and Te(VI) upon its reaction with sodiumborohydride. A continuous flow hydride generation system was developed and parameters that affect the analytical signal were optimized. Sample solutions were prepared in 4.0 mol/L HCl
as reductant 0.5 % (w/v) sodiumborohydride in 0.5 % (w/v) NaOH was used. Quantitative reduction of Te(VI) was achieved through application of a microwave assisted prereduction of Te(VI) in 6.0 mol/L HCl solution. Sensitivity of the system was further enhanced by in-situ trapping of the formed H2Te species in a previously heated graphite furnace whose surface was modified using Pd or Ru. Overall efficiency of pyrolytic coated graphite surface was found to be 15% when hydrides are trapped for 60 seconds at 300 oC. LOD and LOQ values were calculated as 86 pg/mL and 287 pg/mL according to peak height values. Efficiency was increased by 46% and 36% when Pd and Ru modifiers were used, respectively. With Ru modified graphite tube 173 fold enhancement was obtained over 180 seconds trapping period with respect to direct ETAAS. LOD values were 6.4 and 2.2 pg/mL for Pd and Ru treated systems, respectively, for 180 s collection of 9.6 mL sample solution.
Databáze: Networked Digital Library of Theses & Dissertations
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