Speciation of CdTe quantum dots and Te(IV) following oxidative degradation induced by iodide and headspace single-drop microextraction combined with graphite furnace atomic absorption spectrometry

Abstract

A novel speciation method for tellurium present as CdTe quantum dots (CdTe QDs) and Te(IV) in natural waters combining hydride generation with headspace single drop microextraction (HS-SDME) and subsequent measurement by graphite furnace atomic absorption spectrometry has been developed. It was found that NaBH4 is only able to generate H2Te from Te(IV) and not from CdTe QDs. The presence of iodide at high concentration in the acidified sample causes the oxidation of CdTe to Te(IV), thus allowing the simultaneous hydride generation from both species. Furthermore, a gold-containing microdrop exposed to the headspace was found to be an efficient trapping agent for H2Te. Specifically, Au(III) in the drop is reduced by the H2 generated from NaBH4 decomposition forming gold nanoparticles, on which surface H2Te is trapped via catalytic decomposition. Experimental parameters influencing hydride generation, its transport to the headspace and trapping by the drop have been studied. Under optimal conditions, the proposed method yielded detection limits of 0.13 μg L−1 and 0.03 μg L−1 for Te(IV) and total Te [i.e., Te(IV) + CdTe QDs], respectively. Intra-day repeatability and inter-day reproducibility were lower than 4.2% (n = 3) and 9.5% for both measurements, respectively. The method was applied to the analysis of natural waters, namely superficial water, groundwater and lake water, obtaining good recoveries for both Te species.