A new procedure for the determination of 21 macro- and trace elements in human fetal urine using an inductively coupled plasma mass spectrometry with dynamic reaction cell (ICP-DRC-MS) equipped with a micro-flow nebulizer

Accurate Determination of Trace Cadmium in Soil Samples with Graphite Furnace Atomic Absorption Spectrometry Using Metal-Organic Frameworks as Matrix Modifiers

Cadmium (Cd) is a highly toxic heavy metal that is widely distributed in soils at low concentrations. Its volatilization loss occurs at an ashing temperature higher than 350 °C. Accordingly, the accurate determination of its concentration in soils often requires the addition of chemical modifiers by graphite furnace atomic absorption spectrometry (GFAAS) to improve the thermal stability of Cd. In this work, a metal-organic framework (MOF, UIO-66-NH₂) was utilized as a matrix modifier to improve accuracy in determining Cd in soils using GFAAS. The Cd signal, as influenced by drying and pyrolysis temperature and special gas, was also investigated, and the measuring conditions were optimized (2 μg L^-1 Cd concentrations, matrix modifier: UIO-66-NH₂, pyrolysis temperature: 550 °C, atomization temperature: 1650 °C, and special gas: air). The limit of detection (LOD) and the characteristic mass for Cd in soil were 3.84 ng g^-1 and 0.80 pg, respectively. Five soil standard reference materials (SRMs) were analyzed for Cd to verify the effectiveness of the optimized measuring conditions. The soil Cd concentrations obtained were in remarkable agreement with the reference values. Moreover, the mechanism of UIO-66-NH₂ on the graphite platform was investigated in the drying and pyrolysis steps by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). During the drying steps, many functional groups of the matrix were activated, and Cd²⁺ could be captured on its surface. After the pyrolysis step, the structure matrix collapsed and was partially decomposed into ZrO₂, and subsequently, an intermediate state of ZrO₂-(CdO) appeared at high temperatures, which came from the active binding sites on the zirconium oxide octahedron nodes.

Exploitation of 2D Cu-MOF nanosheets as a unique electroactive material for ultrasensitive Cu(II) ion estimation in various real samples

Herein, hybrid carbon sensor has been developed with graphite sheets as a matrix, tricresyl phosphate (TCP) as a plasticizer and nanosheets of 2D Cu-MOF (metal-organic framework) as an electroactive material for the ultrasensitive Cu(II) ion detection in various real samples. Where, the present study proves the efficiency of 2D Cu-MOF as a promising sensing material for the development of Cu(II) ion selective carbon sensor. The developed 2D Cu-MOF nanosheets based sensor containing 2D Cu-MOF: TCP: graphite in the ratio of 2.67: 30.54: 66.79 (% wt/wt) displayed unique Nernstian behavior over two linearity ranges of 1.0 × 10^-11-1.0 × 10^-9 and 1.0 × 10^-5-1.0 × 10^-1 mol L^-1 with slopes of 29.5 ± 0.25 and 29.6 ± 0.13 mV decade^-1, respectively. The fabricated carbon sensor achieved a widely pH independency, fast response time and superior thermal stability with highly selective and ultrasensitive performance. Moreover, It has been efficiently applied for the Cu(II) ion potentiometric estimation in human hair, sesames seeds, two different tea infusions and tap water real samples.