In-tube solid-phase microextraction with a hybrid monolithic column for the preconcentration of ultra-trace metals prior to simultaneous determination by ICP-MS

Thiol-functionalized MOF modified 3D printed monolithic microextraction array for analysis of trace Cd and Pb in human urine

Controlling the position, size, and shape of pores is a limitation of traditional monolithic preparation methods. The application of 3D printing technology offers high customizability, allowing the precise printing of pore positions, sizes, and shapes according to the designer's 3D model. Herein, by using Projection Microstereolithography (PμSL), we prepared a 3D-printed monolithic array with post-modification of thiol-functionalized metal-organic framework (MOF), and combined it with inductively coupled plasma mass spectrometry (ICP-MS) for the online analysis of trace Cd and Pb in human urine. To achieve array monolithic microextraction, six 3D-printed monolithic columns were modified with thiol-functionalized MOF-808 (MOF-808-SH), and were then assembled in the 3D printed extraction device incorporating gas valve and scaffold. The MOF-808-SH modified 3D-printed monolithic column exhibits excellent extraction performance to Cd2+ and Pb2+ due to rich active adsorption sites and hierarchical porous structure, and has long life span (>100 reused times). Under the optimized conditions, the limits of detection (LODs) are 3.5 and 17.6 ng L-1 for Cd2+ and Pb2+, respectively, with the relative standard deviations of 4.9 % and 8.2 % (0.1 μg L-1, n = 7), and the sample throughput is 11 h-1. To validate the accuracy of the method, the method was used to determine Cd and Pb in Certified Reference Materials of freeze-dried human urine, the determined results agree well with the certified values. This method was also successfully applied to the determination of trace Cd and Pb in real human urine samples. The developed method offers low LODs, robust anti-interference capability, high sample throughput, long reuse cycles, and automation analysis, showing great potential for the analysis of trace heavy metals in biological samples.

Synergistic enhancement of Zn-air battery performance via integration of Ni-doped cobalt sulfide nanoparticles within N, S-doped carbon matrix

Exploring precious metal-free bifunctional electrocatalysts for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is essential for the practical application of rechargeable Zn-air battery (ZAB). Herein, Ni-doped Co9S8 nanoparticles embedded in a defect-rich N, S co-doped carbon matrix (d-NixCo9-xS8@NSC) are synthesized via a facile pyrolysis and acid treatment process. The introduction of abundant defects in both the carbon matrix and metal sulfide provides numerous active sites and significantly enhances the electrocatalytic performances for both the ORR and OER. d-NixCo9-xS8@NSC exhibits a superior half-wave potential of 0.841 V vs. RHE for the ORR and delivers a low overpotential of 0.329 V at 10 mA cm-2 for the OER. Additionally, Zn-air secondary battery using d-NixCo9-xS8@NSC as the air cathode displays a higher specific capacity of 734 mAh gZn-1 and a peak power density of 148.03 mW cm-2 compared to those of state-of-the-art Pt/C-RuO2 (673 mAh gZn-1 and 136.9 mW cm-2, respectively). These findings underscore the potential of d-NixCo9-xS8@NSC as a high-performance electrocatalyst for secondary ZABs, offering new perspectives on the design of efficient noble metal-free electrocatalysts for future energy storage and conversion applications.

A comprehensive review of portable syringe systems using micropipette-based extraction techniques for metal analysis

The release of harmful compounds, particularly dangerous metal ions, into the environment has drawn deep concern from the scientific community. Therefore, it has become common in research to evaluate and quantify the harmful concentrations in the presence of these metal ions in several real samples (food, water, and biological samples). To increase sensitivity and lessen the impact of the matrix, sample pretreatment is a helpful strategy to implement before analysis. The limitations of conventional methods have been recently significantly reduced by developing new analytical approaches such as microextraction techniques. The miniaturization of conventional solid-phase extraction (SPE) led to solid-phase microextraction (SPME), drastically reducing both adsorbent use and extraction phase volume. SPME is defined in the present context as a modified extraction technique that employs a portable syringe system attached to micropipette tips. The SPME is considered one of the most appropriate sample preparation tools due to its compatibility with different detection techniques for different metal ions. The current review focuses on SPME based on a portable syringe (attaches to a micropipette tip) system because it has many advantages over conventional solid-phase extraction. It can be designed very simply in a syringe system, a very small quantity of the sorbent has to be kept in the tip, tube, or inside a syringe as a plug and combined with various analytical instruments. Many researchers have designed their own by using homemade tips packed with a sorbent to increase extraction capability and selectivity. According to the current review, there is a lot of potential for increasing the efficacy and efficiency of metal ion extraction from complicated matrices using portable syringe SPME. Studies have shown that when compared to conventional approaches, it performs better in terms of sensitivity, selectivity, and user-friendliness. Furthermore, its application to a wider range of sample types has been enhanced by the flexibility in constructing unique sorbent tips. Conclusively, the developments in portable syringe SPME have addressed several limitations of conventional techniques, positioning it as a robust and versatile tool for environmental monitoring and analysis of hazardous metal ions.

Regulatory roles of APS reductase in Citrobacter sp. XT1-2-2 as a response mechanism to cadmium immobilization in rice

Citrobacter sp. XT1-2-2, a functional microorganism with potential utilization, has the ability to immobilize soil cadmium. In this study, the regulatory gene cysH, as a rate-limiting enzyme in the sulfur metabolic pathway, was selected for functional analysis affecting cadmium immobilization in soil. To verify the effect of APS reductase on CdS formation, the ΔAPS and ΔAPS-com strains were constructed by conjugation transfer. Through TEM analysis, it was found that the adsorption of Cd2+ was affected by the absence of APS reductase in XT1-2-2 strain. The difference analysis of biofilm formation indicated that APS reductase was necessary for cell aggregation and biofilm formation. The p-XRD, XPS and FT-IR analysis revealed that APS reductase played an important role in the cadmium immobilization process of XT1-2-2 strain and promoting the formation of CdS. According to the pot experiments, the cadmium concentration of roots, culms, leaves and grains inoculated with ΔAPS strain was significantly higher than that of wild-type and ΔAPS-com strains, and the cadmium removal ability of ΔAPS strain was significantly lower than that of wild-type strain. The study provided insights into the exploration of new bacterial assisted technique for the remediation and safe production of rice in cadmium-contaminated paddy soils.

Recent advances in solid phase microextraction with various geometries in environmental analysis

Solid phase microextraction (SPME) has emerged as a versatile sample preparation technique for the preconcentration of a broad range of compounds with various polarities, especially in environmental studies. SPME has demonstrated its eco-friendly credentials, significantly reducing the reliance on solvents. The use of biocompatible materials as a coating recipe facilitates the acceptance of SPME devices in analytical chemistry, primarily in the monitoring of environmental pollutants such as persistent organic pollutants (POPs), volatile organic compounds (VOCs), and pesticides from the various environmental matrices. During the last few years, investigators have reported an improvement in the SPME enrichment technique after changing the coating recipe, geometries, and sampling procedure from the complex matrices. Furthermore, the development of various geometries of SPME with large surface areas has enhanced the extraction efficiency of environmental pollutants. As a miniaturized sample preparation technique, SPME significantly reduces the solvent usage, suggesting a potential platform for green chemistry-based research for water, air, and soil analysis. This review article summarizes the evolution of SPME, its various modes, the application of SPME, recent innovations, and prospects for the determination of water, air, and soil pollution. The advantages and disadvantages of SPME in comparison to other extraction techniques have been discussed here. This review serves as a valuable resource for investigators working in sustainable environmental research.

Aptamer based hybrid monolithic pipette tips supported by melamine sponge for enrichment of proteins

BACKGROUND

The convenient preparation and application of functionalized organic-inorganic hybrid monolithic materials have obtained substantial interest in the pretreatment of complex samples by solid-phase extraction (SPE). Compared to the in-tube solid-phase microextraction in fused-silica capillaries, micro SPE in plastic pipette tips have fascinating merits for the easily operated enrichment of trace target analytes from biological samples. However, the poor compatibility of organic-inorganic hybrid monoliths with plastics leads to the rare appearance of commercial hybrid monolithic pipette tips (HMPTs). Therefore, how to synthesize the organic-inorganic hybrid monolithic materials with better extraction performance in plastic pipette tips becomes a challenge.

RESULTS

We develop a facile and cheap strategy to immobilize organic-inorganic hybrid monoliths in pipette tips. Melamine sponge was employed as the supporting skeleton to in situ assemble amine- and thiol-bifunctionalized hybrid monolithic material via "one pot" in a pipette tip, and gold nanoparticles (GNPs) and thiol-modified aptamer against human α-thrombin were sequentially attached to the hybrid monolith within the HMPTs. The average coverage density of the aptamer with GNPs as an intermediary reached as high as 818.5 pmol μL-1. The enriched thrombin concentration was determined by a sensitive enzymatic chromogenic assay with the limit of detection of 2 nM. The extraction recovery of thrombin at 10 nM in human serum was 86.1 % with a relative standard deviation of 6.1 %. This proposed protocol has been applied to the enrichment and determination of thrombin in real serum sample with strong anti-interference ability, low limit of detection and high recovery.

SIGNIFICANCE

The amine- and thiol-bifunctionalized HMPTs prepared with sponge as the skeleton frame provided a novel substrate material to decorate aptamers for efficient enrichment of proteins. This enlightens us that we can take advantage of the tunability of sponge assisted HMPTs to produce and tailor a variety of micro SPE pipette tips for broader applications on the analysis of trace targets in complex biological, clinic and environmental samples.

Smart dual imprinted Origami 3D-ePAD for selective and simultaneous analysis of vanillylmandelic acid and 5-hydroxyindole-3-acetic acid carcinoid cancer biomarkers using graphene quantum dots coated with dual molecularly imprinted polymers

Measuring the levels of the biomarkers vanillylmandelic acid (VMA) and 5-Hydroxyindole-3-acetic acid (5-HIAA) is a valuable tool for clinical diagnosis not only of neuroblastoma or carcinoid syndrome, but also of essential hypertension, depression, migraine, and Tourette's syndrome. Herein, we explore using graphene quantum dots (GQDs) coated with molecularly imprinted polymer (MIP) as novel dual-imprinted sensors for selective and simultaneous determination of VMA and 5-HIAA in urine and plasma samples. The dual-MIP was successfully coated on the GQDs core via co-polymerization of (3-aminopropyl) triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS), acting as functional and cross-linking monomers, respectively. In addition, we successfully created the dual imprinted VMA and 5-HIAA shell on the GQDs' core via a one-pot synthesis. We fabricated a facile and ready-to-use Origami three-dimensional electrochemical paper-based analytical device (Origami 3D-ePAD) for simultaneous determination of VMA and 5-HIAA using a GQDs@dual-MIP modified graphene electrode (GQDs@dual-MIP/SPGE). The Origami 3D-ePAD was designed to form a voltammetric cell on a three-layer foldable sheet with several advantages. For example, they were quickly assembled and enhanced the device's physical durability with the hydrophobic backup sheet. The developed dual imprinted Origami 3D-ePAD leads to substantially enhanced sensitivity and selectivity to electrochemical signal amplification generated from increasing the electrode-specific surface area, electrocatalytic activity, and the large numbers of dual imprinted sites for VMA and 5-HIAA detection. The synthetic recognition sites are highly selective for 5-HIAA and VMA molecules with an imprinting factor of 8.46 and 7.10, respectively. Quantitative analysis relying on square wave voltammetry reveals excellent linear dynamic ranges of around 0.001-25 μM, with detection limits of 0.023 nM for 5-HIAA and 0.047 nM for VMA (3Sb, n = 3). The Origami 3D-ePAD provides high accuracy and precision (i.e., recovery values of 5-HIAA ranged from 82.98 to 98.40 %, and VMA ranged from 83.28 to 104.39 %), and RSD less than 4.37 %) in urine and plasma samples without any evidence of interference. Hence, it is well suited as a facile and ready-to-use disposable device for point-of-care testing. It is straightforward, cost-effective, reproducible, and stable. Furthermore, it allows for rapid analysis (analysis time ∼20s) useful in medical diagnosis and other relevant fields.

Covalent organic frameworks based hierarchical porous hybrid monolithic capillary: Synthesis, characterization, and applications in trace metals analysis

The preparation of hierarchical porous monolithic column with high covalent organic frameworks (COF) loading and micropores accessibility is challenging due to the easy aggregability and sedimentation of COFs. Herein, a novel strategy based on high internal phase emulsion (HIPE) polymerization was proposed for preparing COF hybrid capillary monolithic column with hierarchical porosity. COFs with different frameworks including imine COFs (COF-OMe, COF-F and COF-SH), triazine COF (CTF-1) and boron-based COF (COF-5) were selected to investigate the universality of the preparation strategy. The presence of COF in the monolithic capillary was confirmed by scanning electron microscope, X-ray diffraction and fourier transform infrared spectroscopy. Nitrogen adsorption/desorption experiments and thermogravimetric analysis showed that the prepared COF hybrid monolithic capillary exhibited high COF loading (e.g., 28.7% for COF-SH) and accessibility (e.g., 98.5% for COF-SH), mainly due to the thin walls of void-window structures originated from polymerization of HIPE. The successful preparation of water-stable COF-F, COF-OMe, COF-SH and CTF-1 hybrid monolithic columns demonstrated the proposed synthesis strategy is universal to water-stable COF without tedious optimization of dispersion system, effectively avoiding the sedimentation of COF in pre-polymerization solution. Then, the sulfhydryl-modified COF hybrid polymer (poly(COF-SH-HIPE)) monolithic column was evaluated for the extraction of heavy metal ions, and a method based on poly(COF-SH-HIPE) monolithic capillary microextraction on-line coupled with inductively coupled plasma mass spectrometry detection was developed for analysis of trace Cd, Hg and Pb in human fluid samples.

Organic-silica hybrid monolithic sorbents for sample preparation techniques: A review on advances in synthesis, characterization, and applications

Organic-silica hybrid monolithic materials have attracted considerable attention as potential stationary phases in separation science. These materials combine the advantages of organic polymer and silica-based monoliths, including easy preparation, lower back pressure, high permeability, excellent mechanical strength, thermal stability, and tunable surface chemistry with high surface area and selectivity. The outstanding chromatographic efficiency as stationary phase of hybrid monolithic capillary columns for capillary liquid chromatography and capillary electrochromatography has been reported in many papers. Organic-silica hybrid monolithic materials have also been extensively used in the field of sample preparation. Owing to their surface functionalities, these porous sorbents offer unique selectivity for pre-concentration of different analytes in the most complex matrixes by fast dynamic transport. These sorbents not only improve the analytical method sensitivity, but also introduce novelties in terms of extraction devices and instrument coupling strategies. The current review covers the period spanning from 2017 to 2023 and describes the properties of organic-inorganic hybrid monolithic materials, the present status of this technology and summarizes recent developments in their use as innovative sorbents for microextraction sample preparation techniques (solid phase microextraction with pipette tip, offline in-tube SPME, in-tube SPME online with LC, and in-tube SPME directly coupled with mass spectrometry). Aspects such as the synthesis methods (sol-gel process, one-pot approach, and polyhedral oligomeric silsesquioxanes-based procedure), characterization techniques, and strategies to improve extraction efficiency in various applications in different areas (environmental, food, bioanalysis, and proteomics) are also discussed.

A New Trend and Future Perspectives of the Miniaturization of Conventional Extraction Methods for Elemental Analysis in Different Real Samples: A Review

Sample preparation is one of the viable procedures to be used before analysis to enhance sensitivity and reduce the matrix effect. The current review is mainly emphasized the latest outcome and applications of microextraction techniques based on the miniaturization of the classical conventional methods based on liquid-phase and solid-phase extraction for the quantitative elemental analysis in different real samples. The limitation of the conventional sample preparation methods (liquid and solid phase extraction) has been overcome by developing a new way of reducing size as compared with the conventional system through the miniaturization approach. Miniaturization of the sample preparation techniques has received extensive attention due to its extraction at microlevels, speedy, economical, eco-friendly, and high extraction capability. The growing demand for speedy, economically feasible, and environmentally sound analytical approaches is the main intention to upgrade the conventional procedures apply for sample preparation in environmental investigation. A growing trend of research has been perceived to quantify the trace for elemental analysis in different natures of real samples. This review also recapitulates the current futuristic scenarios for the green and economically viable procedure with special overemphasis and concentrates on eco-friendly miniaturized sample-preparation techniques such as liquid-phase microextraction (LPME) and solid-phase microextraction (SPME). This review also emphasizes the latest progress and applications of the LPME and SPME approach and their future perspective.

Oriented immobilization of antibodies onto sensing platforms - A critical review

The immunosensor has been proven a versatile tool to detect various analytes, such as food contaminants, pathogenic bacteria, antibiotics and biomarkers related to cancer. To fabricate robust and reproducible immunosensors with high sensitivity, the covalent immobilization of immunoglobulins (IgGs) in a site-specific manner contributes to better performance. Instead of the random IgG orientations result from the direct yet non-selective immobilization techniques, this review for the first time introduces the advances of stepwise yet site-selective conjugation strategies to give better biosensing efficiency. Noncovalently adsorbing IgGs is the first but decisive step to interact specifically with the Fc fragment, then following covalent conjugate can fix this uniform and antigens-favorable orientation irreversibly. In this review, we first categorized this stepwise strategy into two parts based on the different noncovalent interactions, namely adhesive layer-mediated interaction onto homofunctional support and layer-free interaction onto heterofunctional support (which displays several different functionalities on its surface that are capable to interact with IgGs). Further, the influence of ligands characteristics (synthesis strategies, spacer requirements and matrices selection) on the heterofunctional support has also been discussed. Finally, conclusions and future perspectives for the real-world application of stepwise covalent conjugation are discussed. This review provides more insights into the fabrication of high-efficiency immunosensor, and special attention has been devoted to the well-orientation of full-length IgGs onto the sensing platform.

Postsynthetic Modification of the Magnetic Zirconium-Organic Framework for Efficient and Rapid Solid-Phase Extraction of DNA

In recent years, several approaches have been applied to modify metal-organic frameworks (MOFs) owing to their excellent structural tunability such as higher extraction efficiency than that of primitive crystals. Herein, Zr-based MOFs (UiO-66-NH₂) with a suitable size modulated by acetic acid were successfully synthesized for effective DNA extraction. The bonding conformations and adsorption mechanism indicated a high affinity between UiO-66-NH₂ and the DNA molecules. Furthermore, Fe₃O₄ nanoparticles were immobilized on the UiO-66-NH₂ surface to allow MOFs with magnetism. The magnetic zirconium-organic framework (MZMOF) retained the intact structure of MOFs and simplified subsequent extraction operations. In the DNA recovery investigation, MZMOF showed high recovery efficiency for both short-stranded DNA (90.4%) and pseudovirus DNA (95.1%). In addition, it showed superior DNA extraction efficiency from plasma (57.6%) and swab preservation solution (86.5%). The prepared MZMOF was employed for highly specific extraction of viral DNA and cfDNA from samples. To further simplify the extraction process, MZMOF was applied to immiscible phase filtration assisted by a surface tension (IFAST) chip for facilitating rapid DNA extraction with sensitive point-of-care testing. The developed MZMOF-based extraction method has significant potential for increasing the demand for rapid and efficient nucleic acid extraction.

Microfluidic sensor integrated with nanochannel liquid conjunct Ag/AgCl reference electrode for trace Pb(II) measurement

Pollution due to heavy metals is becoming increasingly hazardous; therefore, demand for the large-scale deployment of sensor nodes for water quality monitoring has increased. The development of integrated and miniaturised sensors for detecting heavy metals is necessary. Herein, an integrated microfluidic sensor based on a "glass-silicon-glass" sandwich structure is proposed for Pb²⁺ detection. This micro-sensor consists of a nanochannel liquid conjunct Ag/AgCl reference electrode(RE), a working electrode with a three-dimensional Au micropillar array, and a detection chamber for sample measurement. The potential fluctuation of the RE in this sensor was only 0.62% over seven days, remaining relatively stable. Under optimal conditions, the limit of detection and sensitivity for lead were 0.13 μg L^-1 (S/N = 3) and 52.30 nA (μg L^-1)^-1, respectively. The linearity of the sensor for detecting lead was good in the concentration range of 0.50-150 μg L^-1 (R² = 0.9989). Moreover, the proposed microsensor showed high selectivity for Pb²⁺ and achieved sensitive detection of trace Pb²⁺ in different water samples. Therefore, this integrated and miniaturised sensor is a practical tool for trace lead detection, allowing the development of large scale sensor network for water monitoring.

Preparation of a novel amino functionalized ion-imprinted hybrid monolithic column for the selective extraction of trace copper followed by ICP-MS detection

In this work, a novel amino functionalized Cu(II) ion-imprinted organic-inorganic hybrid monolithic column (Cu(II)-IIHMC) was prepared via one-pot co-condensation and the combination of sol-gel and ion-imprinting techniques in a fused capillary. The Cu(II)-IIHMC was used as solid phase microextraction (SPME) matrix followed by inductively coupled plasma-mass spectrometry (ICP-MS) for the analysis of trace Cu(II). The prepared Cu(II)-IIHMC has good mechanical strength, stable imprinting sites and homogeneous structure of network skeleton with large flow-through pores by optimizing the synthesis process. Under the optimized conditions, the Cu(II)-IIHMC can selectively adsorb Cu(II) with the adsorption capacity of 3.13 mg g^-1. With enrichment factor of 10-fold, the calibration curve was established in the range of 0.05-50 μg L^-1 with r² of 0.9992 and the detection limit was 0.008 μg L^-1 for Cu(II). Compared with the non-imprinted hybrid monolithic column (Cu(II)-NIHMC), the Cu(II)-IIHMC possesses better selectivity, anti-interference ability and adsorption capacity. The Cu(II)-IIHMC can specifically capture the target ion in the presence of competitive ions, with the selectivity coefficients exceeding 39.4. The protocol was validated by analyzing Certified Reference Materials of standard sediment, soil and iron ore, and the results were in good agreement with certified values. Moreover, the proposed in-tube SPME procedure can not only preconcentrate trace Cu(II), but also effectively reduce the matrix effect and powerfully eliminate the interference from the main metals in real samples. Therefore, the developed SPME-ICP-MS method with facile preparation, specific selectivity, high sensitivity and efficient analysis, was applied in the determination of trace Cu(II) in environmental and mineral samples with the recoveries of 89.8-111.8% in all spiked samples.

Understanding the relationship between viral infections and trace elements from a metallomics perspective: implications for COVID-19

Recently, the World Health Organization (WHO) declared a pandemic situation due to a new viral infection (COVID-19) caused by a novel virus (Sars-CoV-2). COVID-19 is today the leading cause of death from viral infections in the world. It is known that many elements play important roles in viral infections, both in virus survival, and in the activation of the host's immune system, which depends on the presence of micronutrients to maintain the integrity of its functions. In this sense, the metallome can be an important object of study for understanding viral infections. Therefore, this work presents an overview of the role of trace elements in the immune system and the state of the art in metallomics, highlighting the challenges found in studies focusing on viral infections.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.