Trace determination of lead(II) ions by using a magnetic nanocomposite of the type Fe3O4/TiO2/PPy as a sorbent, and FAAS for quantitation

Three-dimensional tree-like branched TiO2 nanorods for the highly selective enrichment and determination of lead

Branched titanium dioxide nanorods (B-TiO₂ NRs) grown on fluorine-doped tin oxide glass (FTO) were developed, which can be used as a solid-phase extractant for preconcentration and determination of trace Pb(II) combined with inductively coupled plasma optical emission spectrometry (ICP-OES). The B-TiO₂ NR-based glass substrate displayed excellent adsorptive selectivity and capacity for Pb(II); the maximum adsorption capacity was found to be 168.4 mg⋅g^-1 PB(II) at pH = 5.0. It proved that the primary extraction mechanism was attributed to soft acid/soft base interactions to form complexes for chemisorption. Investigating the adsorption kinetics and isotherms indicated that the pseudo-second-order and Langmuir models can better describe Pb(II) adsorption on the B-TiO₂ NRs. The proposed method presented good linearity from 0.01 to 5 mg⋅L^-1 with a correlation coefficient (R²) of 0.9989 and a low limit of detection (LOD) of 2.2 μg⋅L^-1 for Pb(II) under optimal conditions. The method was successfully applied to Pb(II) determination in foodstuffs with desirable recoveries from 93.18 to 108.1% and good precision with an RSD of less than 12.2%. This work provides a new strategy for selective extraction and determination of Pb(II) in complicated matrix samples.

Preparation of a magnetic polystyrene nanocomposite for dispersive solid-phase extraction of copper ions in environmental samples

The core shell nanostructure of magnetic polystyrene (PS@Fe₃O₄) was prepared and its physic-chemical properties were studied FT-IR, SEM, TEM, VSM and BET + BJH. The new adsorbent was applied in the dispersive solid phase extraction technique for measuring copper ions in water, Soil and Oyster samples. Analysis is carried out using a flame atomic absorption spectrometry system. Effective parameters on extraction efficiency, such as pH of extraction solution, sorbent dosage, contact time, concentration and volume of desorption eluent and desorption time were optimized using one at a time method. N₂ adsorption-desorption experiment resulted in high BET surface area (32.002 m² g⁻¹) and large pore volume (0.1794 cm³ g⁻¹) for PS@ Fe₃O₄ nanocomposite. Under the optimum conditions, a calibration curve within the range of 5–40 ng mL⁻¹ with an appropriate coefficient of determination (R²) of 0.9946 was obtained. Preconcentration factor (PF) and limit of detection (LOD) were found to be 55 and 1.6 ng mL⁻¹, respectively. The repeatability and reproducibility for three replicate measurements at the concentration of 25 ng mL⁻¹ were 2.5%–1.4%, respectively. The Freundlich adsorption isotherm and pseudo-second-order kinetic model were consistent to experimental data in adsorption mechanism study. The maximum adsorption capacity was 19.56 mg g⁻¹ for Cu (II). Finally, the efficiency of the method was investigated for analysis of the copper in environmental samples and good relative recoveries (RR%) were obtained within the range of 99.2% to 101.2%.

Highly Permeable Monolith-based Multichannel In-Tip Microextraction Apparatus for Simultaneous Field Sample Preparation of Pesticides and Heavy Metal Ions in Environmental Waters

A portable multichannel in-tip microextraction-based field sample preparation (FSP) apparatus was developed using polymer-based monoliths as an extraction phase. The construction of the FSP device is quite facile and convenient. More specifically, according to the chemical properties of studied analytes, functional-rich and high-permeability monoliths were in situ synthesized in pipet tips. After that, three tips containing the sorbents were mounted to three syringes, which were connected to a screw motor employed to drive the syringes and accurately regulate the flow rates in the adsorption and desorption stages. Because of the multifunction groups in the monoliths, the sorbents displayed satisfactory coextraction performance for pesticides (carbamates and triazoles) and heavy metal ions (Cd²⁺, Pb²⁺, and Cu²⁺) under the optimized conditions. The practicability of the proposed apparatus was demonstrated by the quick and simultaneous FSP of studied analytes in various environmental waters and combined with high-performance liquid chromatography/diode-array detection (for pesticides) and atomic absorption spectrometry (for metal ion) analysis. The results indicated that the limits of detection for the pesticides and metal ions were in the range of 0.36 to 1.2 ng/L and 0.061 to 0.40 ng/L, respectively, with ideal coefficients of determination. Furthermore, the results obtained with the constructed device were quite comparable to those obtained with the traditional laboratory extraction process, which demonstrated that the newly developed apparatus possesses the expected application in the high-throughput FSP of pesticides and heavy metal ions in water samples.

Magnetic Hierarchically Macroporous Emulsion-Templated Poly(acrylic acid)-Iron Oxide Nanocomposite Beads for Water Remediation

Tainting of waterbodies with noxious industrial waste is the gravest environmental concern of the day that continues to wreak inevitable havoc on human health. To cleanup these hard-to-remove life-threatening water contaminants, we have prepared hierarchically porous poly(acrylic acid) beads by emulsion templating. These emulsion-templated macroporous polymer beads not only mediate the synthesis of Fe₃O₄ nanoparticles inside their porous network using a coprecipitation approach but, in turn, create diverse anchoring sites to immobilize an additional poly(acrylic acid) active layer onto the nanocomposite beads. These post-synthetically modified nanocomposite beads with macropores and abundant acrylic acid moieties offer the ready mass transfer and fair advantage of relatively higher overall negative charge to efficiently adsorb lead [Pb(II)] and crystal violet with impressive performance-even superior to many of the materials explored in this regard so far. Furthermore, the strong entanglement of nanoparticles in the porous polymeric scaffolds tackles the curb of trade-off between all-round effective remediation and secondary pollution and the millimeter size eases their processing and recovery during the adsorption tests, thereby making these materials practically worthwhile.

Magnetic boronate modified molecularly imprinted polymers on magnetite microspheres modified with porous TiO2 (Fe3O4@pTiO2@MIP) with enhanced adsorption capacity for glycoproteins and with wide operational pH range

Boronate-affinity based molecularly imprinted polymers (MIPs) are beset by the unsatisfied adsorption capacity and narrow working pH ranges. A magnetic molecularly imprinted polymer containing phenylboronic acid groups was placed on the surface of Fe₃O₄ (magnetite) microspheres coated with porous TiO₂ (Fe₃O₄@pTiO₂@MIP). In contrast to its silica analog (Fe₃O₄@SiO₂@MIP), the flowerlike Fe₃O₄@pTiO₂ offers more binding sites for templates. Thus, the adsorption capacity of the Fe₃O₄@pTiO₂@MIP is strongly enhanced. The strong electron-withdrawing effects of Ti(IV) enable the boronic acid of the MIP to have better affinity for glycoproteins at a wide pH range from 6.0 to 9.0. Consequently, the Fe₃O₄@pTiO₂@MIP exhibits higher adsorption for glycoproteins than Fe₃O₄@SiO₂@MIP in both basic and acidic medium. The Fe₃O₄@pTiO₂@MIPs were eluted with 5% acetic acid aqueous solution containing 30% acetonitrile, and the eluate was analyzed by MALDI-TOF MS. The method was applied to the selective extraction and quantitation of horseradish peroxidase (HRP) in spiked fetal bovine serum (FBS). The linear range is 0.40-10 μg·mL^-1 with the limit of detection of 0.31 μg·mL^-1. In our perception, this work has a wide scope in that is paves the way to a more widespread application of boronate affinity based MIPs for analysis of glycoproteins and related glyco compounds even at moderately acidic pH values. Graphical abstract Schematic presentation of the magnetic boronate modified molecularly imprinted polymer on magnetic spheres modified with porous TiO₂ (Fe₃O₄@pTiO₂@MIP). It was applied to extract glycoprotein in spiked both basic fetal bovine serum (FBS) and acidic urine samples prior to quantitation by MALDI-TOF mass spectrometry.

Speciation analysis of Tl(I) and Tl(III) after magnetic solid phase extraction using a magnetite nanoparticle composite modified with aminodibenzo-18-crown-6 functionalized MIL-101(Cr)

The authors describe a magnetic metal-organic framework nanocomposite consisting of aminodibenzo-18-crown-6 magnetite nanoparticles and MIL-101(Cr). It was employed to the speciation analysis of Tl(I) and Tl(III) ions. The sorbent is capable of selectively extracting Tl(I) while Tl(III) remains in solution. The total amount of thallium was then determined by reducing Tl(III) to Tl(I) by hydroxylamine hydrochloride and also extracting it. The extraction parameters were optimized by employing design of experiments methodology. Thallium was quantified by ET-AAS. Under optimized conditions, the detection limit is as low as 1.5 ng L^-1, the quantification limit is 5.0 ng L^-1, the linear range extends from 5 to 400 ng L^-1, and the relative standard deviation is <12% (for n = 5 at levels of 5, 50 and 250 ng L^-1). The recoveries of real samples analysis were in the range of 90-106%. The method was successfully applied to the analysis of a certified reference material (NIST SRM 1643d water sample) and to various real water samples. Graphical abstract A novel metal-organic framework nanocomposite consisting of aminodibenzo-18-crwon-6 magnetite nanoparticles (Fe₃O₄@ADB18C6) and MIL-101(Cr) was synthesized, characterized and employed to speciation analysis of Tl(I) and Tl(III).

Vortex assisted solid-phase extraction of lead(II) using orthorhombic nanosized Bi2WO6 as a sorbent

Nanosized single crystal orthorhombic Bi₂WO₆ was synthesized by a hydrothermal method and used as a sorbent for vortex assisted solid phase extraction of lead(II). The crystal and molecular structure of the sorbent was examined using XRD, Raman, SEM and SEM-EDX analysis. Various parameters affecting extraction efficiency were optimized by using multivariate design. The effect of diverse ions on the extraction also was studied. Lead was quantified by flame atomic absorption spectrometry (FAAS). The recoveries of lead(II) from spiked samples (at a typical spiking level of 200-400 ng·mL^-1) are >95%. Other figures of merit includes (a) a detection limit of 6 ng·mL^-1, (b) a preconcentration factor of 50, (c) a relative standard deviation of 1.6%, and (d) and adsorption capacity of 6.6 mg·g^-1. The procedure was successfully applied to accurate determination of lead in (spiked) pomegranate and water samples. Graphical abstract Nanosized single crystal orthorhombic Bi₂WO₆ was synthesized and characterized by a hydrothermal method and used as a sorbent for vortex assisted solid phase extraction of lead(II). The procedure was successfully applied to accurate determination of lead in (spiked) pomegranate and water samples.