Sample Preconcentration Research Articles

Single-molecule profiling of per- and polyfluoroalkyl substances by cyclodextrin mediated host-guest interactions within a biological nanopore.

Biological nanopores are increasingly used in molecular sensing due to their single-molecule sensitivity. The detection of per- and polyfluoroalkyl substances (PFAS) like perfluorooctanoic acid and perfluorooctane sulfonic acid is critical due to their environmental prevalence and toxicity. Here, we investigate selective interactions between PFAS and four cyclodextrin (CD) variants (α-, β-, γ-, and 2-hydroxypropyl-γ-CD) within an α-hemolysin nanopore. We demonstrate that PFAS molecules can be electrochemically sensed by interacting with a γ-CD in a nanopore. Using HP-γ-CDs with increased steric resistance, we can identify homologs of the perfluoroalkyl carboxylic acid and the perfluoroalkyl sulfonic acid families and detect common PFAS in drinking water at 0.4 to 2 parts per million levels, which are further lowered to 400 parts per trillion by sample preconcentration. Molecular dynamics simulations reveal the underlying chemical mechanism of PFAS-CD interactions. These insights pave the way toward nanopore-based in situ detection with promises in environmental protection against PFAS pollution.

The Development and Evaluation of Biosorbent Composite Spheres for the Adsorption and Quantification of Copper

Separation techniques are employed to treat and preconcentrate samples. Preconcentration commonly employs adsorption due to the wide range of sorbents available. The biosorbent composite has emerged as a highly effective alternative, primarily due to its selectivity for active sites and its impressive adsorption capability. This study aimed to assess and create a spherical biosorbent composite using cellulose acetate and avocado seed. The purpose of this work was to use a biosorbent composite for copper adsorption by flame atomic absorption spectrometry. The copper adsorption follows the Langmuir isotherm, which indicates that it occurs in a monolayer and is homogeneous. Additionally, the adsorption nature is favorable according to the RL factor. The highest capacity for copper adsorption is 0.121 mg g−1. The report describes the methodology and validation process for quantifying copper. The findings demonstrate that the composite biosorbent enables accurate preconcentration and quantification of copper found in decongestants.

Vortex-assisted dispersive low-density liquid–liquid microextraction of xanthydrol derivatized acrylamide in processed chips and water samples for gas chromatographic analysis

Acrylamide, a probable human carcinogen present in heat-processed foods and environmental contaminants, requires sample extraction and preconcentration before chromatographic analysis. The method developed in this study employed derivatization with xanthydrol and dispersive liquid–liquid microextraction utilizing low-density anisole. Durian or potato chips were combined with deionized water, defatted with hexane, and subjected to precipitation of soluble carbohydrates and proteins using clarification reagents. Water samples were filtered through a membrane filter. Acrylamide was derivatized by introducing an acidic methanolic solution of xanthydrol at 50 °C. The derivatized acrylamide was extracted with 70 µL of anisole and vortexed, with the methanol from the xanthydrol solution serving as the disperser solvent. The anisole layer was analyzed using gas chromatography with both flame ionization and mass spectrometric detection. Linear calibration plots exhibited coefficients of determination >0.9997. The precision was measured at <10% RSD, and recoveries ranged from 84% to 107%. The quantitation limit varied from 2 to 10 µg kg−1 for processed chips and from 0.05 to 0.10 µg L−1 for water samples. Acrylamide was detected in all processed chip samples, with some concentrations exceeding the benchmark value of 750 μg kg−1. However, no acrylamide was identified in any of the water samples.

Recent advances in capillary electrophoresis-mass spectrometry analysis of ‍trace biomolecules

In recent years, various trace bioanalysis methods have been developed, including single-cell transcriptome analysis methods. As the sample volume and amount of biomolecules contained therein are extremely limited, development of new single-cell analysis methods require extremely high-level techniques. It is necessary to design an appropriate analysis system that integrates a highly sensitive detection system and a pretreatment protocol for minimizing sample loss, where separation method is especially important for analyzing diverse mixtures of biomolecules. Among them, capillary electrophoresis (CE) can separate biomolecules in nanoliter-scale solutions with high resolution, making it highly compatible with trace samples such as single cells. By combining with highly sensitive nano-electrospray ionization-mass spectrometry (MS), it is possible to detect nanomolar to sub-nanomolar biomolecules, which can be further improved by using online sample preconcentration methods. These highly sensitive analytical techniques have made it possible to analyze trace amounts of metabolites, proteins, lipids, etc. This review paper summarizes the research on CE-MS trace bioanalysis that has been reported to date, with a focus on single-cell analysis.

Novel Triton X-114 coated Fe3O4 magnetic nanoparticle adsorbent for Cd(II) and Co(II) ions preconcentration in honey samples using magnetic solid-phase extraction: Determination by ICP-OES

This work focuses on creating and studying the effectiveness of Fe3O4 nanoparticles coated with (3-aminopropyl)triethoxysilane (APTES) and polyethylene glycol tert-octylphenyl ether (TX-114), respectively, as adsorbent. Fe3O4@APTES@TX-114 adsorbent extracts heavy metal cations Cd2+ and Co2+ using a magnetic solid phase extraction technique. The synthesized magnetic nanoparticles (MNPs) were characterized by Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray Analysis (EDX), Fourier Transform Infrared Spectroscopy (FT-IR), and Thermogravimetric Analysis (TGA). After this stage, Cd2+ and Co2+ determinations were made with the ICP-OES device. The optimum conditions for recovering Cd2+ and Co2+ cations were pH 7, an adsorbent dosage of 2 g/L, and a contact time of 120 min. While the method was compatible with Langmuir and Freundlich isotherm models, the pseudo-second-order kinetic equation was more compatible than the pseudo-first-order. Acidic and basic media were investigated for the desorption of Cd2+ and Co2+ ions from the adsorbent. At the same time, maximum recovery was achieved for both cations at a concentration of 1.5 mol/L HCl, but no significant recovery was obtained in the NaOH medium. The common ion study observed that Cd2+ and Co2+ cations were recovered over 95 % in the presence of many cations and anions at different concentrations. The relative standard deviation (RSD), limit of quantification (LOQ), limit of detection (LOD), and enrichment factor (EF) were calculated as 1.40 %, 2.963 µg/L, 0.889 µg/L, 20.99 for Cd2+ and 3.05 %, 1.88 µg/L, 0.564 µg/L, 109.41 for Co2+, respectively. The magnetic solid phase extraction method realized quantitative recovery of Cd2+ and Co2+ cations in different honey samples. It was found that the heavy metal contents in honey samples from the Sakarya region are below permissible levels.

Combination of on-line sample preconcentration by large-volume dual preconcentration by isotachophoresis and stacking (LDIS) with field-amplified sample injection (FASI) on Y-channel microchips.

In our previous study, the combination of two on-line sample preconcentration techniques, large-volume sample stacking with an electroosmotic flow (EOF) pump (LVSEP) and transient isotachophoresis (tITP), in microchip electrophoresis (MCE) was developed, which was named large-volume dual preconcentration by isotachophoresis and stacking (LDIS). LDIS was apparently effective for improving the sensitivity and the peak shape. In LDIS, however, there was a limit to the improvement of the sensitivity enhancement factor (SEF) since the amount of analytes to be concentrated was limited to the channel volume. To overcome this issue, in the present article, LDIS was coupled with field-amplified sample injection (FASI) technique on Y-shaped channel microchips. The use of a Y-channel in LDIS-FASI allowed consecutive LVSEP, FASI and tITP enrichments with a simple voltage control. In conventional LVSEP and LDIS analyses of a standard analyte, the SEFs were evaluated to be 2630 and 13,100, respectively, whereas in LDIS-FASI that was increased to 27,900 even at the FASI injection time of 0s. To achieve higher SEFs, furthermore, the FASI injection time was increased to 150s, resulting in the best SEF of 58,500. It should be emphasized that the peak width in LDIS-FASI was quite narrow, only 0.3-3.1s, while in normal LVSEP that was 13s. Furthermore, the LDIS-FASI technique was applied to the analysis of oligosaccharide mixture. Due to the focusing effect by LDIS-FASI, the resolutions were improved from 0.97-1.57 to 2.08-2.73.

From Farm to Fork: Enhancing Agricultural and Food Safety Monitoring with Laser-Engineered Graphene Sensors

In the critical fields of precision agriculture and food safety, the demand for accurate and sensitive monitoring tools for fertilizers, pesticides, and food-borne pathogens cannot be overstated. Our collaborative research with commercial entities seeks to overcome the challenges faced by current electrochemical ion-selective, enzymatic, and immunosensors, which often fall short in selectivity, stability, and sensitivity, particularly under field conditions. We showcase the tunable properties of Laser-Induced Graphene (LIG) – such as surface wettability, roughness/area, and electrical conductivity – and their instrumental role in enhancing the commercial viability of these sensor technologies.We demonstrate the conversion of hydrophilic Laser-Induced Graphene (LIG) to a near-superhydrophobic state using an innovative dual-laser process in ambient conditions. This method intricately sculpts the surface into micro and nanoscale structures reminiscent of a lotus leaf, resulting in nearly superhydrophobic characteristics. By modifying the laser's power, speed, and fluence, we can also fine-tune the electroactive surface area and electrical conductivity, significantly impacting sensor functionality. For solid contact ion-selective electrodes (SC-ISEs), enhancing the LIG surface with high hydrophobicity prevents water layer accumulation at the ion-selective membrane and electrode interface. This design expels water from within the membrane, fosters stronger membrane-electrode adhesion, and consequently, diminishes signal interference. Such improvements are instrumental in boosting the sensor's accuracy and extending its operational lifespan. In contrast, a hydrophilic LIG with a large surface area enhances catalytic efficiency and allows more biorecognition agents to adhere to its surface, thereby amplifying the sensitivity of enzymatic pesticide sensors. Lastly, a flat, hydrophilic LIG surface ensures an even distribution of antibodies, which enhances the performance of sensors detecting foodborne pathogens.These modifications to LIG and the resulting sensors have substantial commercial potential. We have developed ions sensors for nitrate, ammonium, potassium, calcium, and magnesium have demonstrated near-Nernstian sensitivities, extensive sensing ranges across four orders of magnitude, and the ability to detect concentrations as low as 1 ppm in soil and water samples. These sensors are currently being integrated into commercial soil moisture and temperature probes for monitoring in farm fields. The pesticide sensing capability of the sensor can reach an extremely low picomolar detect limit for organophosphates, the nanomolar regime for neonicotinoids, and micromolar regime for glyphosate in surface waters. These sensors are currently being interfaced with LIG-based mist/fog harvesting devices to monitor pesticide and spray drift in farm fields. Finally, the LIG-based Salmonella sensors are capable of monitoring bacteria such as Salmonella to about 10 CFU/mL in actual food matrices such as chicken broth without the need for sample preconcentration or costly lab analyses.This research forges innovative avenues in agriculture and food safety monitoring, laying the groundwork for mass production of efficient and economical sensors. We believe this technology will revolutionize field monitoring, significantly advancing sustainable agriculture and improving public health safety. Figure 1

Preconcentration of nanoplastics using micro-electromembrane extraction across free liquid membranes

Asymmetric micro-electromembrane extraction (µ-EME) based on a free liquid membrane has been evaluated for the preconcentration of nanoplastics. A conical unit (200 µL micropipette tip) enabled the simple and reproducible formation of the required three-phase extraction system consisting of a donor solution (150 µL sample/standard solution), free liquid membrane (FLM; 10 µL 1-pentanol), and an acceptor solution (5 µL of 5 mM phosphate buffer, pH 10.7). After µ-EME, nanoplastics transferred across the FLM into the acceptor solution were quantified using capillary zone electrophoresis with diode array detection. Enrichment factors >20 and extraction recoveries >70 % were achieved for nanoplastics concentrated at 500 V during 5 min. The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) of the method using 200 nm sulphonated polystyrene particles as model nanoplastics were 6.00×10−4% (w/v) and 2.00×10−3% (w/v), respectively. Intraday (n = 6) and interday (n = 6) repeatability%RSD for 5.5 × 10−3% (w/v) nanoplastics were 8.5 % and 7.2 %, respectively. µ-EME enabled an efficient sample matrix clean-up and preconcentration of nanoplastics spiked in tea sample matrices. Nanoplastics preconcentrated through the FLM for black tea resulted in an enrichment factor of 20±3.6 (n = 3), with complete sample matrix removal of UV absorbing compounds.

Determination of amino acids and peptides without their pre-column derivatization by capillary electrophoresis with ultraviolet and contactless conductivity detection. An overview.

This review provides an overview of recent works focusing on the determination of amino acids (AAs) and peptides using capillary electrophoresis with contactless conductivity detection and ultraviolet (UV) detection, which is the most widespread detection in capillary electromigration techniques, without pre-capillary derivatization. Available options for the UV detection of these analytes, such as indirect detection, complexation with transition metal ions, and in-capillary derivatization are described. Developments in the field of direct detection of UV-absorbing AAs and peptides as well as progress in chiral separation are described. A separate section is dedicated to using on-line sample preconcentration methods combined with capillary electrophoresis-UV.

Development of an ecofriendly dispersive liquid phase microextraction method for the preconcentration of β-blockers in waste and environmental samples

Effective sample preparation is crucial in instrumental analysis to enhance selectivity, sensitivity, and instrument protection. The current trend of miniaturization in liquid–liquid extraction aims to conserve solvents and promote environmental sustainability. Liquid phase microextraction, requiring only small volumes of the extractant, facilitates sample preconcentration without the need for evaporation and reconstitution. This study presents the development of an eco-friendly dispersive liquid–liquid microextraction method employing solidification of floating organic droplets for the determination of five β-blocker drugs in waste and environmental samples. The optimization of key variables affecting extraction efficiency, including extractant type and volume, pH of the diluent, dispersion technique, vortexing, and centrifugation time, was carried out. Optimal results were achieved using 50 μL of dodecanol as the extractant, 1 min of vortexing for dispersion, followed by 2 min of centrifugation for phase separation. The sample was then subjected to a 5 min cooling in an ice bath to solidify the dodecanol before UHPLC/UV analysis. The method yielded enrichment factors within the range of 23–55. The applicability of this approach was demonstrated in laboratory waste and environmental water analysis, with acceptable % recoveries ranging from 98.07 % to 101.83 % and %RSD below 1.96. Moreover, we assessed the method’s performance and greenness with ComplexGAPI, BAGI, and carbon footprint. This method not only provides high efficiency and reliability but also aligns with the principles of sustainablility.

Unveiling New Arsenic Compounds in Plants via Tailored 2D-RP-HPLC Separation with ICP and ESI MS Detection.

Arsenic (As) speciation analysis is scientifically relevant due to the pivotal role the As chemical form plays in toxicity, which, in turn, directly influences the effect it has on the environment. The objective of this study was to develop and optimize a method tailored for studying As compounds in plant samples. Different extraction procedures and HPLC methods were explored to assess their efficiency, determine mass balance, and improve the resolution of compounds in the chromatograms. Conventionally applied anion-exchange chromatography facilitated the separation of well-documented As compounds in the extracts corresponding to 19 to 82% of As present in extracts. To gain insight into compounds which remain undetectable by anion chromatography (18 to 81% of As in the extracts), but still possibly metabolically relevant, we explored an alternative chromatographic approach. The procedure of sample purification and preconcentration through solid-phase extraction, facilitating the detection of those minor As compounds, was developed. The system was further refined to achieve an online 2D-RP-HPLC system, which was employed to analyze the extracts more comprehensively with ICP and ESI MS. Using this newly developed method, As(III)-phytochelatins, along with other arseno-thio-compounds, were detected and identified in extracts derived from the tree roots of seedlings grown in the presence of As(III) and As(V), and a group of arseno lipids was detected in the roots of plants exposed to As(V).

Development and characterization of a non-enzymatic electrochemical biosensor for rapid determination of sorbent-based extracted trazodone and doxepin in complicated samples

BackgroundGiven the importance of achieving optimal therapeutical concentration in patients treated with antidepressants, this study investigates a novel technique for the simultaneous determination of trazodone (TRZ) and doxepin (DOX) in human plasma and serum samples for the first time. ResultsTo achieve simultaneous determination of two antidepressants, TRZ and DOX, a novel detection system was designed: a non-enzymatic voltammetric biosensor based on boron-reduced graphene oxide/manganese oxide nanoparticles (GCE/B-rGO/MnO NPs). The detection was accomplished after pre-concentration and extraction trace amounts of the analytes using the thin film-solid phase microextraction (TF-SPME) technique, which employed polyvinyl alcohol/polyvinyl acetate/copper oxide nanoparticles (PVA/PVAc/CuO NPs) electrospun nanofibers.The successful preparation of composite nanofibers and modified electrodes was confirmed using the evaluation of field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX). Also, the composite nanofibers were characterized with attenuated total reflectance-Fourier transform-infrared (ATR-FT-IR) and X-ray diffraction (XRD). In the solution of TRZ and DOX, under optimum experimental conditions, the linear dynamic ranges (LDRs) were 0.1–20.0 μmol L−1 and 0.5–27.0 μmol L−1, respectively. Also, the limit of detection (LOD) values of TRZ and DOX were 0.032 and 0.150 μmol L−1. SignificancePVAc acts as a cross-linking agent for PVA, and their mixture is effective for sample preparation and pre-concentration of analytes in complex matrices. Also, adding CuO NPs to this polymeric mixture enhanced the adsorption efficiency.Taking advantage of the high surface area of MnO NPs and the high electrical conductivity of B-rGO, and considering the superiority of their simultaneous utilization, the constructed electrochemical biosensor is both cost-effective and rapid. It demonstrates excellent stability, repeatability, and sensitivity for the simultaneous determination of TRZ and DOX under optimal conditions.This biosensor, the first of its kind, is specifically designed for the simultaneous determination of TRZ and DOX in human plasma and serum samples, representing a significant advancement in biosensing technology.

3D Paper-Based Origami Device for Programmable Multifold Analyte Preconcentration.

In analytical chemistry, preconcentration represents a critical step able to enhance the accuracy of detection; however, the experimental procedures needed to preconcentrate samples might be characterized by drawbacks regarding the whole analytical process, e.g., being complex, invasive, and/or time-consuming. In this study, a novel 3D paper-based origami device is introduced for multifold analyte preconcentration. Leveraging the benefits of paper-based substrates, the proposed architecture boosts sample preconcentration while minimizing time and tasks for measurements, solely by exploiting the porous and versatile nature of paper-based substrates. In comparison with other paper-based approaches reported in the literature for preconcentration, the present architecture offers the ability to be programmed for obtaining the needed sensitivity increase without sacrificing measurement time. To demonstrate the efficacy of the novel approach, the 3D paper-based origami device was deeply characterized, including the most relevant parameters, i.e., disk size and number, unfolding time, and volume, and subsequently applied for the preconcentration and the detection of various analytes in real matrices, namely, mercury in tap water and glucose in sweat, resulting in a 400% and 300% sensitivity enhancement, respectively. This innovative preconcentration tool addresses the limitations of existing conventional methods, providing increased sensitivity without the use of expensive and time-consuming procedures through only exploiting the intrinsic properties of paper-based substrates and a rationale design. The proposed architecture emerges as a universal tool to be adopted and programmed for various analytical systems and fields of application.

High enrichment factors in chemical analysis of progestins and in bioassays: insights beyond trace levels.

Concerns are growing about adverse effects of progestins on biota, even at ultra-trace concentrations. The enrichment factor (EF) from extraction of analytes in environmental samples that is needed for sample pre-concentration can affect not only performance of the analytical method but also the matrix effect. Therefore, the present study aimed to assess the influence of high sample EF on performance of the high-performance liquid chromatography with atmospheric pressure chemical ionization and photoionization coupled with high-resolution mass spectrometry (HPLC-APCI/APPI-HRMS) method for analysis of progestins in waste water treatment plant (WWTP) effluents and surface waters and analysis of (anti-)progestogenic activities measured by (anti-)PR-CALUX bioassays. The results showed that HPLC-APCI/APPI-HRMS coupled with solid-phase extraction and a high EF (33,333 Lwater/Lextract) enabled the detection of more compounds compared to samples with lower sample EF (10,000 Lwater/Lextract). The matrix effect did not increase proportionally compared to lower EFs (10,000 and 16,666 Lwater/Lextract), and lower limits of quantification were achieved in WWTP effluents and surface waters. The results of bioassays have shown that relative EF of 25 Lwater/Lbioassay appears high enough to detect progestogenic activity in treated waste water. Our study is one of the first to provide insights into sample pre-concentration in analysis of progestins and progestogenicity in aquatic environments.

Application of on-line sample preconcentration by large-volume dual preconcentration by isotachophoresis and stacking (LDIS) on straight-channel microchips.

In this study, large-volume dual preconcentration by isotachophoresis and stacking (LDIS) which is an on-line sample preconcentration technique coupling large-volume sample stacking with an electroosmotic flow pump (LVSEP) with transient isotachophoresis (tITP) was applied to microchip electrophoresis (MCE) for improving both detection sensitivities and peak shapes. To realize LDIS in MCE, we investigated experimental procedures for injecting a short plug of a leading electrolyte (LE) solution into a straight microchannel without any sophisticated injector apparatus. We found that a short LE plug could be injected into a sample-filled straight-channel only by making the liquid level of the LE solution in an outlet reservoir higher than that in an inlet one. By applying a reversed-polarity voltage to the microchip, anionic analytes injected throughout the microchannel were first enriched by LVSEP, followed by tITP. Through the second preconcentration effect by tITP in LDIS, sensitivity enhancement factor (SEF) and asymmetry factor for a standard dye were improved from 878 and 0.62 to 1330 and 1.14, respectively, relative to those in conventional LVSEP. It should be noted that more viscous running buffer containing sieving polymers could be employed to the LDIS analysis, which was effective for improving the SEF and the separation efficiencies, especially for bio-polymeric compounds. Finally, LDIS was applied to the oligosaccharide and protein analyses in MCE, resulting in the SEFs of 1410 and ca. 50 for maltotriose and bovine milk casein, respectively.

Wastewater-based monitoring of the nitazene analogues: First detection of protonitazene in wastewater

Synthetic opioids, particularly the nitazene analogues class, have become a public health concern due to their high potency. Wastewater-based epidemiology can detect community use of these compounds. The objective of this work was to detect nitazene analogues in wastewater from samples collected from eight sites in the United States. Influent wastewater samples were collected from eight sites in seven states (Arizona, Oregon, New Mexico, Illinois, New Jersey, Washington and Georgia) in the United States. Samples were collected from each site on three days between 27 December 2022 and 4 January 2023, acidified on collection, stored frozen and shipped to Arizona State University (Tempe, AZ) for sample processing. Samples were then shipped to The University of Queensland (Brisbane, Australia) for sample analysis. Protonitazene was found in samples collected from two sites in Washington and Illinois. The concentration was estimated up to 0.5 ng/L, with estimated excreted mass loads up to 0.3 mg/day/1000 people. This work has shown that it is possible to detect nitazene analogues in wastewater using a combination of sample pre-concentration and sensitive instrumentation, thereby further expanding the utility of wastewater-based epidemiology.

Optimization of a pre-concentration method for the analysis of mercury isotopes in low-concentration foliar samples.

Hg isotope analysis in samples from background regions is constrained by the presence of low Hg concentration and therefore requires a pre-concentration method. Existing Hg pre-concentration methods are constrained by long sample processing time and limited sample loading capacity. Using foliar samples as a test case, an optimized Hg pre-concentration method is presented that involves the microwave-assisted digestion of samples for Hg isotope analysis with the addition of a pre-digestion step. Microwave-digested foliar samples and CRMs were transferred to an impinger, reduced with SnCl2, and collected in a 2.25 mL concentrated inverse aqua regia (3:1 HNO3:HCl, v/v). This resulted in an optimal acid concentration in the solution ideal for analysis on MC-ICP-MS. The time for purging with Hg-free N2 was optimized to 30 min and the efficiency of the pre-concentration method was tested using a combination of approaches. Tests performed on pure reagents and matrix of foliar samples spiked with 197Hg radiotracer showed recoveries averaging 99 ± 1.7% and 100 ± 3.0%, respectively. Mercury at concentrations as low as 1.83 ng g-1 was pre-concentrated by digesting aliquots of foliage samples in individual digestion vessels. Recoveries following their pre-concentration averaged 99 ± 6.0%, whereas recoveries of 95 ± 4.7% and 95 ± 2.5% were achieved for NIST SRM 1575a (pine needle) and reagents spiked with NIST SRM 3133, respectively. Analysis using multicollector-ICP-MS showed low fractionation of δ202Hg during sample pre-concentration with no significant mass-independent fractionation. The proposed method is a relatively simple and robust way to prepare Hg samples for Hg isotopic analysis and is suitable even for complex biological matrices.

VALIDAÇÃO DE MÉTODO ANALÍTICO PARA QUANTIFICAÇÃO DOS ESTRÓGENOS NATURAIS (E1, E2 E E3) E SINTÉTICO (EE2) EM ÁGUA SUPERFICIAL E MATERIAL PARTICULADO EM SUSPENSÃO DE UM ESTUÁRIO SUBTROPICAL DO ATLÂNTICO SUL, BRASIL

VALIDATION OF ANALYTICAL METHOD FOR QUANTIFICATION OF NATURAL ESTROGENS (E1, E2, AND E3) AND SYNTHETIC (EE2) IN SURFACE WATERS AND SUSPENDED PARTICULATE MATERIAL OF A SOUTH ATLANTIC SUBTROPICAL ESTUARY, BRAZIL. Marine pollution has become relevant for coastal conservation units and ecosystems of great ecological importance. This study validated analytical methods to investigate the occurrence of the emerging contaminants 17β-estradiol (E2), estrone (E1), estriol (E3), and 17α-ethinylestradiol (EE2) in surface waters and suspended particulate matter (SPM) from Guaratuba Bay, South Atlantic, Brazil. The analysis was performed by liquid chromatography coupled to a fluorescence detector (LC-FLD) after pre-concentration of surface water samples by solid phase extraction (SPE) or solid-liquid extraction for SPM samples. The recovery percentages were between 48 and 87%, and the coefficient of variation (CV) between 3 and 24% for SPM and from 64 to 107% (CV of 4 to 42%) for surface water. The method thus proved to be accurate and precise at the concentrations studied (ng g-1 and µg L-1). The concentration ranged from 10 to 177 ng L-1 in surface waters and from 392 to 4108 ng g-1 in SPM. E2, EE2, and E3 were found in SPM under different climatic conditions and population occupation. EE2 was determined in all sampling campaigns, especially in summer, when the number of tourists increases considerably. The presence of EE2 in the SPM of Guaratuba Bay warns for possible implications for the health of coastal environments.

Strongly coupled plasmonic metal nanoparticles with reversible pH-responsiveness and highly reproducible SERS in solution.

We report a facile method to prepare polymer-grafted plasmonic metal nanoparticles (NPs) that exhibit pH-responsive surface-enhanced Raman scattering (SERS). The concept is based on the use of pH-responsive polymers, such as poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH), as multidentate ligands to wrap around the surface of NPs instead of forming polymer brushes. Upon changing the solvent quality, the grafted pH-responsive polymers would drive reversible aggregation of NPs, leading to a decreased interparticle distance. This creates numerous hot spots, resulting in a secondary enhancement of SERS as compared to the SERS from discrete NPs. For negatively charged PAA-grafted NPs, the SERS response at pH 2.5 showed a secondary enhancement of up to 104-fold as compared to the response for discrete NPs at pH 12. Similarly, positively charged PAH-grafted AuNPs showed an opposite response to pH. We demonstrated that enhanced SERS with thiol-containing and charged molecular probes was indeed from the pH-driven solubility change of polymer ligands. Our method is different from the conventional SERS sensors in the solid state. With pH-responsive polymer-grafted NPs, SERS can be performed in solution with high reproducibility and sensitivity but without the need for sample pre-concentration. These findings could pave the way for innovative designs of polymer ligands for metal NPs where polymer ligands do not compromise interparticle plasmon coupling.

Molecularly Imprinted Polymers (MIPs): Bibliometric Analysis

Separation techniques can be applied to sample clean up and preconcentration processes which are key steps in analytical methods to improve the characteristic performance for the separation and detection of various analytes. Selection of the right sorbent with higher selectivity is the main objective of analysis proposed by Molecularly Imprinted Polymers (MIPs). MIPs is a separation technique are prepared by reaction sequences containing a template, one or two functional monomers, one/two crosslinking monomers, polymerization initiator in a solvent containing solution. Various studies on MIPs have been carried out because MIPs have many advantages over other methods, especially as a selective adsorbent for sample preconcentration. The aim of this study is to comprehensively and systematically examine and present bibliometric data analysis using VOSViewer using Scopus article data. it is possible to infer that VOSviewer may be used as a tool for bibliometric data analysis, whereas Publish or Perish can be utilized as a reference management tool for collecting research article data on "molecularly imprinted polymers." The data utilized in this study to analyze data with VOSviewer is research on "molecularly imprinted polymers" from the Scopus database. The total number of publications acquired relevant to the issue was 200 documents spanning the years 2018-2023. Between 2018 and 2023, the amount of research on molecularly imprinted polymers published in Scopus-indexed journals declined. The network visualization depicts the evolution map of molecularly imprinted polymers, which is separated into four clusters. Cluster 1 contains 128 topics, Cluster 2 contains 95 topics, Cluster 3 contains 90 topics, and Cluster 4 contains 73 items. So, the total number of terms in this study is 386 from four clusters.