Abstract
Trace metals in the environmental matrices may provide benefit or risk to humans, as well as other living organisms. Normally, environmental policies regulate maximum allowed total metal concentrations that may be toxic to living organisms. However, this approach has been criticized due to failure to consider the different toxicities that occur when metals exist in different species. Therefore, it is necessary to determine the chemical forms (species) of the element, because different species of the same metal can range from essential to innocuous to toxic. Therefore, the main objective of this project is to develop sample preparation techniques for speciation of V, Mo, Se Te and Sb in environmental samples prior to spectrometric determinations. The sample preparations methods include suspended solid phase extraction (SDSPME), dispersive liquid-liquid microextraction (DLLME) and ultrasound-assisted dispersive solid phase microextraction (UADSPME).
A rapid and efficient preconcentration method for speciation of Mo (VI), Sb (V) and V (V) that is based on ligandless ultrasound-assisted dispersive solid phase microextraction (UADSPME) using Fe3O4@Al2O3 nanoparticles (NPs) as a sorbent was developed. The NPs were characterized using XRD, SEM, EDX and surface area (BET). The experimental parameters affecting the preconcetration system were optimized using fractional factorial design. The target analytes quantified by inductively coupled plasma spectrometry (ICP-OES). Under optimum conditions, the developed method displayed relatively low limits of detection and quantification, good repeatability (intra-day precision) and reproducibility (inter-day precision). Finally, a non-chromatographic method was developed for speciation of Mo, Sb, and V at trace levels and successfully applied for the determination of analytes in environmental water samples. On the other hand, suspended dispersive solid phase microextraction combined with inductively coupled plasma spectrometric determination was used for speciation of inorganic selenium in water samples. Nano-alumina modified with Aliquat 336 was used as a solid phase materials. The developed method was found to be selective to Se(IV). The SDSPME procedure displayed excellent analytical figures of merit such as linearity, low LODs and LOQs, high precision and accuracy as well as high sample throughput.
Dispersive liquid-liquid microextraction (DLLME) was used for speciation of tellurium in wastewater and surface water samples. A multivariate approach was used for optimization of experimental parameters affecting the speciation of Te. Under the...
M.Tech. (Chemistry)