Hydride generation and preconcentration of bismuth on a single-drop followed by determination using electrothermal atomic absorption spectrometry

Dügencili, Başak
A novel method for determination of bismuth is proposed where the analyte is converted to its hydride form, BiH3, followed by head space preconcentration on a single aqueous drop; final detection was done using electrothermal atomic absorption spectrometry (ETAAS). The preconcentration step was named as headspace single-drop microextraction (HS-SDME). Experimental parameters for hydride generation using both continuous flow and batch technique, ETAAS and finally HS-SDME were optimized. For HS-SDME, Pd, Ni, Au or Pt was used as matrix modifiers (MMs) with a concentration of 5.0 mg/L. In hydride generation, sample was prepared in 1.0 mol/L HCl, reductant was 1.0 mL of 0.5% (w/v) NaBH4 stabilized in 0.2% (w/v) NaOH. 3.0 µL of 10.0 µL of selected MM in 1.0% HNO3 was exposed to analyte vapors in head-space mode. Au was selected as the best MM where the detection limit was found to be 0.005 ng/mL using a sample of 5.0 mL. vi Nonspectral interference effects for some species were studied. Regarding the hydride forming species, the effects of As(III), Se(IV), Sb(III), Sn(IV), Te(VI) and Pb(II) were investigated. In the presence of As(III), Se(IV) and Sb(III), the analyte signal was suppressed when interferant/analyte mass ratio was as high as 1000; Sn(IV), Te(VI) and Pb(II) did not have any significant interference effect using the same conditions. Among the transition elements, Co, Cu and Zn seemed to have a suppressing effect while Cr, Mn and Fe had a much lower effect. Regarding the effects of some ubiquitous ions, Ca2+and Mg2+ had no significant effect while Al3+ , Na+ and PO43- had higher effect on analyte signal. The developed method was applied to tap water, bottled water and mineral water samples; it was observed that standard additions would be needed for desired accuracy. Using NIST 1643e “Trace elements in water” standard reference material, satisfactory accuracy was obtained.