Date

2014

Author

Njie, Njaw

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Speciation analysis is important for arsenic. Novel methods to improve the sensitivity for determination of total arsenic and arsenic speciation have been developed. The techniques basically rely on generation of volatile arsenic species by reaction with sodium borohydride followed by trapping on a W-coil atomizer and finally releasing analyte atoms by heating the atomizer; the system is named as W-coil atom trapping electrothermal atomic absorption spectrometry (WC-ETAAS). Sample solution may be introduced both by continuous flow hydride generation (CF-HG-WC-ETAAS) or flow injection hydride generation (FI-HG-WC-ETAAS). Speciation analysis was performed by using high pressure liquid chromatography (HPLC) for separation followed by W-coil trapping; this method is named as HPLC-HG-WC-ETAAS. For optimization and comparison, an electrically heated quartz tube atomizer was also used for the systems named CF-HG-EHQTA-AAS and FI-HG-EHQTA-AAS. Both for FI and HPLC systems, rapid on-line reduction of As(V) to As(III) was realized by using 1.0% (v/v) thioglycollic acid in 0.002 mol/L HCl. In HPLC analyses, the collection of analyte was done only for As(III) and As(V), these species were then collected and then atomized consecutively. The results are used to determine total inorganic arsenic content. The optimized temperatures for collection and atomization temperatures for W-coil were 720 ºC and 1920 ºC, respectively. Using CF-HG-WCETAAS and 180 s collection of 19.5 mL sample, limits of detection limits for As(III) and As(V) were 1.9 ng/L and 1.8 ng/L, respectively. For speciation analysis by HPLCHG- WC-ETAAS, limits of detection were 0.25 ng/mL and 0.30 ng/mL for As(III) and As(V), respectively; a sample loop of 0.16 mL was used. For testing accuracy, Waste Water EU-L-2, Trace Elements in Water 1643e, Trace Elements in Spinach Leaves1570aand Tuna Fish Tissue BCR627 were used as certified reference materials. Applications on real samples were carried out on irrigation water, dill, lettuce, garden rocket and parsley. The methods developed offer novel alternatives in arsenic determination and speciation using only a simple atomic absorption spectrometer.

Subject Keywords

Arsenic., Arsenates., Tungsten compounds., Atomic absorption spectroscopy.

URI

http://etd.lib.metu.edu.tr/upload/12617642/index.pdf
https://hdl.handle.net/11511/23804

Collections

Graduate School of Natural and Applied Sciences, Thesis