Date

2017

Author

Mercan, Pınar

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Tungsten coil (W-coil) has become an alternative tool for graphite tubes in atomic spectrometry for its high melting point, good electrical conductivity and low cost. Tungsten coil systems have been used in atomic spectrometry as both atomizers and vaporizers. Both approaches include advantages and disadvantages. In this work the behaviors of both approaches were investigated. Bismuth (Bi), one of the hydride forming elements, was selected as the analyte. The properties and performances of both techniques, namely electrothermal atomizer (ETA) and electrothermal vaporizer (ETV), were studied regarding analytical efficiency, interferences and practicability. In this study, W-coil was used as an atom trap for preconcentration and atomization/revolatilization of volatile species of Bi, using hydride generation technique. In W-coil Atom Trap ETA system, the collected analyte species were atomized directly, since the W-coil was functioning as atomizer. In the system where W-coil was used as a vaporizer (W-coil Atom Trap ETV) the collected analyte vi species were revolatilized rapidly and sent to quartz T-tube atomizer for measurement. The experimental parameters were optimized for Bi with rhodium coated W-coil Atom Trap ETA and syringe attached rhodium coated W-coil atom trap ETA where the limits of detection obtained for this system were 0.046 and 0.018 ng/mL for 120 s trapping, respectively. Moreover, conditions for rhodium coated Atom Trap ETV and syringe attached rhodium coated W-coil Atom Trap ETV systems were optimized; the limits of detection for these systems were 0.047 and 0.026 ng/mL for 120 s trapping, respectively. In literature, interferences of ETA and ETV systems have been investigated separately; however, any study regarding the comparison of interferences for both approaches has not been performed. In this study the interferences were studied by comparing the trends exhibited by both of the approaches. In order to understand the nature of the interference, a twin-channel hydride generation system containing two gas liquid separators was used. For Rh coated W-coil atom trap ETA system, among the selected interference elements, Te and Sb suppressed significantly the signals. On the other hand, Rh coated W-coil atom trap ETV system for Bi had a completely different behavior pattern compared to Rh coated W-coil atom trap ETA system. By using the twin-channel system, a detailed interference study with Rh coated W-coil atom trap ETV system was carried out. It was found that As, Se and Sb enhanced the analytical signal of Bi significantly and the interferences most probably took place in the revolatilization stage.

Subject Keywords

Bismuth., Hydrides., Tungsten., Electric coils., Atomic spectroscopy.

URI

http://etd.lib.metu.edu.tr/upload/12620877/index.pdf
https://hdl.handle.net/11511/26328

Collections

Graduate School of Natural and Applied Sciences, Thesis