Speciation studies of trace metals in environmental samples, using spectrometric techniques

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

Nanostructured materials as sorbents for sample preparation in trace metal analysis

Abstract: Trace metals pollution of the environment is a global challenge. This is because these may be a health risk to humans, as well as other living organisms. Metals such as As, Co, Cr, Cd, Pb, Tl, Te, Sb, are regarded as toxic inorganic pollutants. These metals normally exist at trace levels in various environmental matrices such as, soil, water and biological samples to name a few. Toxic metals can cause severe health problems that can even lead to fatalities for animals and human beings, this is due to the fact that unlike organic contaminants these trace toxic metal ions are non-biodegradable and have a tendency to accumulate in vital human organs, such as liver, lungs, heart and kidneys. Therefore, the aim of this research was to prepare a nanostructured material and applied as an effective adsorbent for preconcentration of trace from complex matrices. The quantification of the trace metals was achieved using inductively coupled plasma optical emission spectrometry (ICP-OES) technique. The nanocomposites were then characterized using scanning electron microscopy (SEM), Fourier Transform infrared (FTIR) spectroscopy transmission electron microscopy (TEM), and x-ray diffraction (XRD). Several effective experimental parameters controlling the preconcentration of the trace metals were optimized using central composite design. Under optimum conditions they showed good the linearity ranged, correlation of coefficients (R2), limits of detection (LODs) and quantification (LOQs). The prepared adsorbents are Mg/Al-LDH@CNTs nanocomposite, MPC@SiO2@Fe3O4, and Fe3O4@Mg/Al-layered double hydroxide were characterized and used to develop three preconcentration methods which are mainly ultrasound assisted solid phase extraction using magnetic and dispersive ultrasound-assisted cloud point- dispersive μ-solid phase extraction...Ph.D. (Chemistry

Recent Advances in Synthesising and Applying Magnetic Ion-Imprinted Polymers to Detect, Pre-Concentrate, and Remove Heavy Metals in Various Matrices

Magnetic ion-imprinted polymers (MIIPs) are an innovative material that combines the selectivity of ion imprinting with the ease of separation provided by magnetic properties. Recent advancements in MIIPs have shown that they have higher selectivity coefficients compared to non-imprinted materials. The synthesis of MIIPs involves creating specific recognition sites for target ions in magnetic nanomaterials. Various nanomaterials, such as graphene oxide, carbon nanotubes, and silica, have been incorporated into the IIPs to improve their analytical performance for different environmental applications, including metal extraction, monitoring, detection, and quantification. This review stresses the need to develop new monomers with a high affinity for the target analyte and to find supporting materials with groups that facilitate the effective removal of the target analyte. It also explores the influence of experimental parameters on metal determination

Removal of Oxyanions and Trace Metals from River Water Samples Using Magnetic Biopolymer/Halloysite Nanocomposites

The presence of metallic pollutants presents a significant risk to human health, making their removal crucial. Magnetic halloysite nanotube (HNT@Fe3O4) nanocomposite was synthesised via co-precipitation, and then magnetic hydrogel (Fe3O4@HNT-SA and Fe3O4@HNT-CTS) nanocomposites were prepared using chitosan (CTS) and sodium alginate (SA) biopolymers. The structural, morphological, crystalline, surface, and thermal properties of the hydrogels were determined. The favourable adsorption performance of Fe3O4@HNT-SA and Fe3O4@HNT-CTS hydrogels towards As, Cd, Cr, Mo, Pb, Sb and V was established by optimising the factors affecting the sorption process. The results indicated that Fe3O4@HNT-CTS was suitable for the adsorption of As, Cr, Mo, Sb and V, while Fe3O4@HNT-SA had high adsorption affinity for Cd and Pb. The data for the adsorption of target analytes onto the hydrogels were mostly explained by both the Langmuir isotherm model and the pseudo-second order model. The maximum adsorption capacities of Fe3O4@HNT-SA hydrogel for Cd and Pb were 52.2 mg/g and 57.7 mg/g, respectively. On the other hand, the maximum capacities of the Fe3O4@HNT-CTS hydrogel for As, Cr, Mo, Sb, and V were 30.3 mg/g, 28.4 mg/g, 22.2 mg/g, 24.7 mg/g, and 19.9 mg/g, respectively. The Fe3O4@HNT-SA and Fe3O4@HNT-CTS hydrogels effectively removed the respective target analytes from river water samples

Development of ultrasound-assisted dispersive solid-phase microextraction based on mesoporous carbon coated with silica@iron oxide nanocomposite for preconcentration of Te and Tl in natural water systems

The main objective of this study was to develop an ultrasound-assisted dispersive solid-phase microextraction (UADSPME) method for separation and preconcentration of tellurium (Te) and thallium (Tl) in environmental samples prior to inductively coupled plasma-optical emission spectrometry determination. The MPC@SiO2@Fe3O4 nanocomposite was used as a nanoadsorbent in the UADSPME method. The nanocomposite was prepared using a coprecipitation and sol–gel method, and it was characterized using scanning electron microscopy/energy-dispersive X-ray spectroscopy, transmission electron microscopy and X-ray powder diffraction techniques. The Box–Behnken design and response surface methodology were used for the optimization of experimental parameters (such as pH, extraction time and mass of adsorbent) affecting the preconcentration procedure. Under optimized conditions, the limits of detection were 0.05 and 0.02 µg L−1 and the limits of quantification were 0.17 and 0.07 µg L−1 for Te and Tl, respectively. The precision expressed as the relative standard deviation (%RSD) was 2.5% and 2.8% for Te and Tl, respectively. Finally, the developed method was applied for the analysis of Tl and Te in real samples

Seasonal Variation of Drinking Water Quality and Human Health Risk Assessment: A Case Study in Rural Village of the Eastern Cape, South Africa

Contamination of drinking water by metals remains a global threat to living organisms. Therefore, the current study describes variations of metal occurrence, water quality and human health risk assessment between the dry and wet seasons of a rural village located in the Eastern Cape Province, South Africa. The concentrations of major and trace metals were determined in drinking water samples using inductively coupled plasma-optical emission spectrometry (ICP-OES). The physicochemical parameters, water quality index (WQI), total water hardness (TWH) and health risk assessment (hazard quotient: HQ and chronic daily intake: CDI) were evaluated seasonally. The TWH results showed that the water was very hard with water hardness values ranging between 415 and 442. The water also contained several metals and metalloids such as Al (2.18–3.36 mg L−1), As (0.17–0. 53 mg L−1), Cd (0.0068–0.0134 mg L−1), Cr (0.2481–0.2601 mg L−1), Mn (0.387–1.582 mg L−1), Pb (0.064–0.0802 mg L−1), Sb (0.0496–0.1391 mg L−1) and Se (0.075–0.148 mg L−1) that exceeded the SANS and WHO permissible limits in drinking water. The health risk assessment revealed that the water may cause noncarcinogenic and carcinogenic health effects due to the presence of As, Cr, Sb, Tl and V in water samples, while the water quality index revealed that the water was of very poor quality.</jats:p

Development of ultrasound-assisted dispersive solid-phase microextraction based on mesoporous carbon coated with silica@iron oxide nanocomposite for preconcentration of Te and Tl in natural water systems

Abstract The main objective of this study was to develop an ultrasound-assisted dispersive solid-phase microextraction (UADSPME) method for separation and preconcentration of tellurium (Te) and thallium (Tl) in environmental samples prior to inductively coupled plasma-optical emission spectrometry determination. The MPC@SiO2@Fe3O4 nanocomposite was used as a nanoadsorbent in the UADSPME method. The nanocomposite was prepared using a coprecipitation and sol–gel method, and it was characterized using scanning electron microscopy/energy-dispersive X-ray spectroscopy, transmission electron microscopy and X-ray powder diffraction techniques. The Box–Behnken design and response surface methodology were used for the optimization of experimental parameters (such as pH, extraction time and mass of adsorbent) affecting the preconcentration procedure. Under optimized conditions, the limits of detection were 0.05 and 0.02 µg L−1 and the limits of quantification were 0.17 and 0.07 µg L−1 for Te and Tl, respectively. The precision expressed as the relative standard deviation (%RSD) was 2.5% and 2.8% for Te and Tl, respectively. Finally, the developed method was applied for the analysis of Tl and Te in real samples.</jats:p