Aqueous Environmental Samples Research Articles

Red-Emitting Polymerizable Guanidinium Dyes as Fluorescent Probes in Molecularly Imprinted Polymers for Glyphosate Detection

The development of methodologies to sense glyphosate has gained momentum due to its toxicological and ecotoxicological effects. In this work, a red-emitting and polymerizable guanidinium benzoxadiazole probe was developed for the fluorescence detection of glyphosate. The interaction of the fluorescent probe and the tetrabutylammonium salt of glyphosate was studied via UV/vis absorption and fluorescence spectroscopy in chloroform and acetonitrile. The selective recognition of glyphosate was achieved by preparing molecularly imprinted polymers, able to discriminate against other common herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D) and 3,6-dichloro-2-methoxybenzoic acid (dicamba), as thin layers on submicron silica particles. The limits of detection of 4.8 µM and 0.6 µM were obtained for the sensing of glyphosate in chloroform and acetonitrile, respectively. The reported system shows promise for future application in the sensing of glyphosate through further optimization of the dye and the implementation of a biphasic assay with water/organic solvent mixtures for sensing in aqueous environmental samples.

Tannic acid as a chemosensor for colorimetric detection of Fe(II) and Au(III) ions in environmental water samples

AbstractA simple and efficient method to detect and quantify Fe(II) and Au(III) cations in environmental water samples was developed. The detection principle is based on the 1:1 mol‐ratio complex formation between the probe molecule (tannic acid, TA) and Fe(II)/or Au(III), which yields visual color change and strong light absorbance at 518 nm and 534 nm, respectively. The association constant Ka for Fe(II) and Au(III) cations 4.01 × 104 and 4.13 × 104 M−1, respectively, was determined from Benesi–Hildebrand plot, indicating strong interactions between TA and target ions. This TA probe performed well in 50 mM phosphate buffer (PB, pH 9.0) solution and demonstrated an outstanding selectivity over 16 potential interfering metal ions and a good selectivity over Fe(III). The linear range in this study for Fe(II) and Au(III) cations was 0.25–100 μM and 1.0–100 μM, respectively. The detection limit of the TA probe for Fe(II) and Au(III) cations was found to be 0.080 and 0.50 μM, respectively. The spike recovery for both metal ions in three environmental aqueous samples (spring water and pond water) was ranged 90.2%–117.2%. This study demonstrated that the TA probe is a simple and convenient detection method for analyzing water samples obtained from fresh water sources.

Silver-capped selenium explored as an electro-catalyst for simultaneous detection of nitro-aromatic drugs in different aqueous samples

Herein, we have fabricated silver (Ag) over selenium (Se) to explore its enriched electrochemical performance towards the simultaneous detection of nitro-aromatic drugs (nitrofurantoin (NFT) and P-nitrophenol (P-NP)). Due to its synergistic effect, Ag/Se modified GCE showed excellent electro-catalytic activity compared to other electrodes. Well-defined and divergent reduction peaks were obtained at −0.49 V (NFT) and −0.85 V (P-NP) with a detection range of 0.9 V at Ag/Se/GCE. It withholds an extensive linear range of 0.1 to 210 µM for NFT and 0.1 to 150 µM for P-NP with a nanomolar level detection limit of 23.87 nM L−1 & 7.82 nM L−1; an appraisable sensitivity of 1.138 µA µM−1 cm−2 & 2.86 µA µM−1 cm−2 for NFT and P-NP, respectively. Interestingly, the electrode possesses a high selectivity in the presence of biomolecules, nitro drugs, and metal ions. Examination of nitro-aromatic drug contamination on water sources shows a massive peril to human life and marine environs due to its adverse hazardous effects. Further, the fabricated Ag/Se-based electrochemical sensor was exposed to various environmental aqueous samples to detect NFT& P-NP which has demonstrated an exquisite recovery results in practical feasibility. Thereby confirms that Ag/Se-based electrochemical sensors have boundless potential for ecological investigations and sensing applications.

Amino-functional metal–organic framework as a general applicable adsorbent for simultaneous enrichment of nine neonicotinoids

Four functional metal–organic frameworks (MOFs) were facilely synthesized through one-pot procedure or post-synthetic modification method and used as adsorbents for simultaneous enrichment of nine neonicotinoids (NEOs) for the first time. Of which, amino-functional MIL-101-NH2 showed general high affinity towards nine NEOs and performed the best due to extraordinarily high surface area and specific interaction with analytes. A simple, efficient and robust method was developed by dispersive solid phase extraction with MIL-101-NH2 combining with liquid chromatography mass spectrometry (dSPE-LC-MS). Key factors that affecting enrichment efficiency were investigated and the established method demonstrated high sensitivity with detection limits as low as 0.02–0.1 ng/mL and wide linearity range over 3–4 orders of magnitude. Besides, compared with commercial SPE cartridges, this adsorbent showed superior enrichment efficiency and could be used for at least five times without obvious recovery decrease. The method was also applied for determination of trace NEOs in aqueous environmental samples and NEO contamination was found. This study demonstrated the practicability of facile synthetic MOF in simultaneous enrichment of nine NEOs and offered a simple and general method for trace amount NEOs sample preparation in real samples.

Wanted not, wasted not: Searching for non-target taxa in environmental DNA metabarcoding by-catch

Metabarcoding of environmental DNA is based on primers specific to the target taxa (e.g. bacteria, zooplankton, fishes). However, because of commonly used protocols, regardless of the chosen primers, several sequences of non-target species will inevitably be generated, but are usually discarded in commonly used bioinformatics pipelines. These non-target sequences might contain important biological information about the presence of other species in the studied habitats and its potential for ecological studies is still poorly understood. Here, we analyzed the presence of mammal and bird species in aquatic environmental samples that were originally amplified targeting teleost fish species. After all cleaning and checking steps, we kept 21 amplicon sequence variants (ASVs) belonging to mammals and ten to birds. Most ASVs were taxonomically assigned to farm/domestic animals, such as cats, cows, and ducks. Yet, we were able to identify a native semi-aquatic mammal, the capybara, in the samples. Four native bird species and a non-native potentially invasive bird (Corvus sp.) were also detected. Although the data derived from these samples for mammals and birds are of limited use for diversity analyses, our results show the potential of aquatic samples to characterize non-aquatic birds and highlight the possible presence of a potentially invasive species that had not been recorded before in the region.

Microwave-assisted green synthesis of multi-functional carbon quantum dots as efficient fluorescence sensor for ultra-trace level monitoring of ammonia in environmental water

This study reports a facile green preparation of self-assembled multi-functional carbon quantum dots (CQDs) via direct pyrolysis technique coupled with microwave-assisted synthesis using Ziziphus Mauritiana stone biomass (as a bio-resource precursor). The synthesized multi-functional CQDs was characterized using FT-IR, XRD, XPS, TEM, and fluorescence spectroscopy techniques. The results exhibit that the prepared CQDs are spherical-shaped with an average diameter of 2–4 nm and showed bright bluish-green emissions property with stable dispersion and high photostability in the aqueous medium. Furthermore, the emission properties of CQDs were examined by quenched with ammonia (NH3) and other molecules in aqueous media. Results indicated that the developed CQDs showed effective fluorescent for the selective and sensitive detection (sensor) of NH3 with a detection limit of 10 nM. Thus, the presented procedure is a simple, low-cost, efficient, chemical-free synthesis of CQDs and can be applied as selective and sensitive (sensor) monitoring of NH3 concentration in aquatic environmental samples.

Stability properties of natural estrogen conjugates in different aqueous samples at room temperature and tips for sample storage

It is important to keep natural estrogen conjugates (C-NEs) intact in aqueous environmental sample before sample preparation; otherwise, this may influence the accurate determination of NEs. Therefore, this work thoroughly investigated the stability of C-NEs in three different aqueous environmental samples under four different storage conditions, room temperature, low temperature of 4 °C, low pH of 3, and addition of HgCl2 at 2 g/L. Results showed that C-NEs in aqueous sample were easily deconjugated under low temperature of 4 °C, which has been widely used in sample collection and storage. Both the low pH of 3 and addition of HgCl2 at 2 g/L under room temperature could keep C-NEs intact in domestic wastewaters and river water within 36 h, but the latter could keep C-NEs stable longer. This work is the first to show that low pH of 3 alone could keep C-NEs intact, which suggested that the combined condition at low temperature of 4 °C that has been widely used could be omitted. Meanwhile, compared to pH adjustment, addition of 2 g/L HgCl2 into aqueous sample is more convenient and practical for 24-h composite sampling, which may be widely applied.

A selective colorimetric chemosensor for detection of Cu(II) ions in aqueous samples

In this work we report a selective colorimetric chemosensor (S) for Cu 2+ ion detection in aqueous media. It has been synthesized by a condensation reaction between 1-hydrazinophtalazine and 6,6 ′ -dihydroxy-5,5 ′ dimethoxy-(1,1 ′ -biphenyl)-3,3 ′ -dicarbaldehyde. The interaction between S and Cu 2+ was studied and the results showed a bathochromic shift at 420 nm in UV–Vis spectra. The absorbance enhancement of S was attributed to complex formation with Cu 2+ by 2:1 stoichiometry. The proposed analytical method can be applied to Cu 2+ quantification with a linear range covering from 5.0 to 315.8μM, and can be used to routinely analyze Cu 2+ in environmental aqueous samples with satisfactory results.

Efficient nested-PCR-based method development for detection and genotype identification of Acanthamoeba from a small volume of aquatic environmental sample

Acanthamoeba spp. are opportunistic human pathogens that cause granulomatous amoebic encephalitis and keratitis, and their accurate detection and enumeration in environmental samples is a challenge. In addition, information regarding the genotyping of Acanthamoeba spp. using various PCR methods is equally critical. Therefore, considering the diverse niches of habitats, it is necessary to develop an even more efficient genotyping method for Acanthamoeba spp. detection. This study improved the sensitivity of detection to avoid underestimation of Acanthamoeba spp. occurrence in aquatic environmental samples, and to accurately define the pathogenic risk by developing an efficient PCR method. In this study, a new nested genotyping method was established and compared with various PCR-based methods using in silico, lab, and empirical tests. The in silico test showed that many PCR-based methods could not successfully align specific genotypes of Acanthamoeba, except for the newly designed nested PCR and real-time PCR method. Furthermore, 52 water samples from rivers, reservoirs, and a river basin in Taiwan were analysed by six different PCR methods and compared for genotyping and detection efficiency of Acanthamoeba. The newly developed nested-PCR-based method of genotyping was found to be significantly sensitive as it could effectively detect the occurrence of Acanthamoeba spp., which was underestimated by the JDP-PCR method. Additionally, the present results are consistent with previous studies indicating that the high prevalence of Acanthamoeba in the aquatic environment of Taiwan is attributed to the commonly found T4 genotype. Ultimately, we report the development of a small volume procedure, which is a combination of recent genotyping PCR and conventional real-time PCR for enumeration of aquatic Acanthamoeba and acquirement of biologically meaningful genotyping information. We anticipate that the newly developed detection method will contribute to the precise estimation, evaluation, and reduction of the contamination risk of pathogenic Acanthamoeba spp., which is regularly found in the water resources utilised for domestic purposes.

Impact of gadolinium oxide with functionalized carbon nanosphere: A portable advanced electrocatalyst for pesticide detection in aqueous environmental samples

In this study, we developed a portable electrochemical sensor for realizing the pesticide residue in biological, environmental, and vegetable samples. A lower concentration of carbendazim pesticide (CBZ) was electrochemically exposed by newly developed gadolinium oxide/functionalized carbon nanosphere modified glassy carbon electrode (Gd2O3/f-CNS/GCE). The Gd2O3/f-CNS composite was prepared by two-pot ultrasonic-assisted co-precipitation method and characterized by various physicochemical analytical techniques. In addition, the electrocatalytic activity of the composite was investigated by cyclic voltammetry (CV) towards the detection of CBZ. Besides, the Gd2O3/f-CNS/GCE exhibited excellent electrocatalytic capability and sensitivity towards the oxidation of CBZ due to its high electrochemical active surface area, good conductivity, and fast electron transfer ability. A wide linear range of CBZ (0.5–552 μM) was attained with a low level of detection (LOD) of 0.009 μM L−1 and exceptional stability of 93.41%. The proposed sensor exemplifies practical feasibility in blood serum, water, and vegetable samples with an remarkable recovery range of 96.27–99.44% and primary current response of ∼91% after 15 days.

Effect of operating variables on the separation of radiostrontium from aqueous matrices with ion-selective solid-phase extraction systems

Radiostrontium (r-Sr: 90Sr) is one of the primary fission products in nuclear power plants and generates liquid radioactive waste when intermixed to the aqueous matrix. Therefore, separation or preconcentration of r-Sr from the aqueous matrices is necessary for environmental monitoring or nuclear forensics. The solid-phase extraction (SPE) approach is prevalently used for r-Sr isolation and to design matrix-specific methods, while generalized SPE-assisted operating protocols are not proposed by far. In the current work, four different SPEs, namely AnaLig Sr-01, Eichrom Sr, Triskem TK100, and Eichrom DGA, were evaluated for selective separation of Sr from aqueous matrices. Operating variables, e.g., solution acidity, washing solvent, eluent-type or volume, loading or elution flow-rate, were varied to optimize the SPEs performance. The objective was to ascertain the operating variables for maximum Sr-separation yield from aqueous environmental samples with the SPEs mentioned above. In addition, the Sr-separation efficiency of SPEs was evaluated by calculating the separation factor (SFSr/M) between Sr and interfering elements to r-Sr (M = Ca, Mg, Ba, or Y), and the Sr-retention capacity of the SPEs was determined. Finally, the optimized operating variables for the evaluated SPEs were used to construct protocols for r-Sr separation from aqueous matrices. Real 90Sr contaminated aqueous samples from the Chernobyl nuclear power plant cooling pond were treated by those protocols, and the results are validated comparing with the IAEA-recommended classical protocol. All the SPEs were able to isolate Sr at varying extents from matrices at the optimum conditions, even at much higher contents of interfering elements. Eichrom Sr or AnaLig Sr-01 showed better Sr-retention capability among the SPEs, while Triskem TK100 showed superiority over other SPEs regarding Sr-selectivity.

A study on structural evolution of hybrid humic Acids-SiO2 nanostructures in pure water: Effects on physico-chemical and functional properties

Humic acids (HA) are considered a promising and inexpensive source for novel multifunctional materials for a huge range of applications. However, aggregation and degradation phenomena in aqueous environment prevent from their full exploitation. A valid strategy to address these issues relies on combining HA moieties at the molecular scale with an inorganic nanostructured component, leading to more stable hybrid nanomaterials with tunable functionalities. Indeed, chemical composition of HA can determine their interactions with the inorganic constituent in the hybrid nanoparticles and consequently affect their overall physico-chemical properties, including their stability and functional properties in aqueous environment. As a fundamental contribution to HA materials-based technology, this study aims at unveiling this aspect. To this purpose, SiO2 nanoparticles have been chosen as a model platform and three different HAs extracted from composted biomasses, manure (HA_Man), artichoke residues (HA_Art) and coffee grounds (HA_Cof), were employed to synthetize hybrid HA-SiO2 nanoparticles through in-situ sol-gel synthesis. Prepared samples were submitted to aging in water to assess their stability.Furthermore, antioxidant properties and physico-chemical properties of both as prepared and aged samples in aqueous environment were assessed through Scanning Electron Microscopy (SEM), N2 physisorption, Simultaneous Thermogravimetric (TGA) and Differential Scanning Calorimetric (DSC) Analysis, Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR), Electron Paramagnetic Resonance (EPR) spectroscopies.The experimental results highlighted that hybrid HA-SiO2 nanostructures acted as dynamic systems which exhibit structural supramolecular reorganization during aging in aqueous environment with marked effects on physico-chemical and functional properties, including improved antioxidant activity. Obtained results enlighten a unique aspect of interactions between HA and inorganic nanoparticles that could be useful to predict their behavior in aqueous environment.Furthermore, the proposed approach traces a technological route for the exploitation of organic biowaste in the design of hybrid nanomaterials, providing a significant contribution to the development of waste to wealth strategies based on humic substances.

Comprehensive Assessment and Potential Ecological Risk of Trace Element Pollution (As, Ni, Co and Cr) in Aquatic Environmental Samples from an Industrialized Area.

A global assessment of arsenic (As), nickel (Ni), cobalt (Co) and chromium (Cr) was performed in environmental samples from an important industrial bay. Different fractions of water, sediments and tissues from four species of fish were analysed. Samples were collected from selected sampling sites during four consecutive samplings in spring and autumn seasons, in order to evaluate concentrations and their possible correlations among the aquatic compartments. While a higher availability of Cr and Ni was found in water, Co and As were the most available elements in sediments. In fish, the liver was the tissue with the highest proportion of As and Co, and gills showed the highest concentrations of Ni and Cr. Significance differences were observed among sites showing the pollution sources. In sediments, high correlations were found between total Co content and the most available fractions. Total Ni content highly correlated with the oxidisable fraction, while Cr total content tightly correlated with the least available fractions. Quality guideline values for sediments were frequently exceeded. In sediments and biota, concentrations were slightly higher than in other ecosystems, indicating that maritime, industrial and urban activities are affecting this type of ecosystem with great anthropogenic influence.

Morphological transformation assisted switchable deep eutectic solvents combined with HPLC-DAD for the detection of six UV-filters in surface and bathing waters

Detection of ultraviolet (UV) filters in environmental matrices has aroused great interest; however, most relevant analytic approaches lack efficiency and convenience. Herein, a ‘green’ fatty acid-based deep eutectic solvent (FA-DES), with both the ‘switchability’ (between hydrophobicity and hydrophilicity) and proper melting points for solidification was synthesized to preconcentrate/extract six UV filters in river, lake, sea, and bathing water samples. The switchable FA-DES acts as both the extractant and disperser, thereby reducing the overall solvent consumption. Strong electrolytes and effervescence produced in-situ during ‘switch’ propelled the lipophilic UV filters salting out and mass-transferring from aqueous phase to DES phase. Quick solidification of FA-DES after extraction realized thorough phase separation with less analyte loss and transfer errors. Overall, these advantageous characteristics are conductive to the superior extraction performance of FA-DES for UV-filters. Synthesizing conditions of the selected DES and extraction parameters were optimized by central composite design (CCD) and univariate analysis. Under the optimum conditions, the limits of detection (LOD) and recovery for six UV-filters in real samples were in the range of 0.021–0.336 μg/L and 86.2–116.6%, respectively. Overall, the proposed methodology is eco-friendly, efficient, convenient and cost-effective, and thus has promising prospect for quantitative analysis of diverse UV-filters in various environmental aqueous samples. For instance, the method can be utilized to monitor the concentration level of UV-filters in swimming pools, lidos, and recreational water.

Visual Method for Selective Detection of Hg2+ Based on the Competitive Interactions of 2-Thiobarbituric Acid with Au Nanoparticles and Hg2+

A facile visual strategy is presented for specific identification of mercury ions (Hg2+) in an aqueous environment based on the competitive interactions of 2-thiobarbituric acid (TBA) with Au nanoparticles (AuNPs) and Hg2+. This approach depends on the unique optical performance of AuNPs and the sulfophile affinity of AuNPs and Hg2+. With the addition of TBA, AuNPs aggregate because of the ligand exchange between surface-loaded citrate ions of AuNPs and the thiol group of TBA, which induces a red shift in the absorption spectrum, and the color changes to blue from wine red. However, the added Hg2+ in advance can restrain the agglomeration of AuNPs induced by TBA since the mercaptan group is more likely to react with Hg2+ than AuNPs through the formation of Hg2+ sulfur. Based on the competitive interactions of TBA with AuNPs and Hg2+, the method can specifically detect Hg2+ in the absence of masking reagents without reacting with the major interfering metal ions including Cu2+, Pb2+, and Cd2+ compared to previous studies. Moreover, the detection limit of this original method can be as low as 2.4 nM, and it can be effectively used for Hg2+ detection in environmental aqueous samples.

Spectroscopic detection of Hg2+ in water samples using fluorescent carbon quantum dots as sensing probe

Mercury (Hg2+) is remarked as toxic and hazardous element to global environment. Here, carbon quantum dots (CQDs) were synthesized by simple microwave assisted technique for Hg2+ detection in water samples via. fluorescence quenching and FT-IR spectroscopic approach. The morphology and chemical structure of synthesized CQDs was investigated by TEM, FT-IR, 13C-NMR, fluorescence and UV-vis spectroscopic technique. The resultant CQDs bears spherical morphology with an average size of 2–4 nm. The binding parameters, as Stern-Volmer quenching constant (Ksv) and binding constant for CQDs-Hg system was investigated by fluorescence method, whereas UV-vis techniques was employed for determination of thermodynamic parameters, as Gibb’s free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) at three different temperature (295, 298 and 305 K). Moreover, selectivity assay for Hg2+ detection has been studied in presence of other metal ions by FT-IR as well as fluorescence spectroscopy. Analytical assay was also successfully applied for Hg2+ in spiked water samples collected from different areas of Chhattisgarh, with 98–99 recovery %. The detection of Hg2+ has been demonstrated in the range of 0 to 5.0μM with 3.25 nM detection limit. The present method is found to be simple, highly sensitive and selective for sensing of Hg2+ in aquatic environmental samples using CQDs as sensing probe.

Determination of polar benzotriazoles in aqueous environmental samples by hollow-fibre microextraction method with LC-MS/MS and its comparison to a conventional solid-phase extraction method

A hollow-fibre liquid-phase microextraction method (HF-LPME) was developed for the extraction of polar benzotriazoles from aqueous samples. In combination with LC-MS/MS determination, the method was also validated for environmental waters. Several parameters were optimized, with solvent selection and sample pH having the greatest influence on the enrichment factors. Reduced enrichment factors were observed in HF-LPME from natural waters compared to deionized water, but this was successfully overcome by the addition of 0.20 mM EDTA. Due to matrix effects of up to ±62%, a matrix-matched calibration in river water was used. In terms of its efficacy and applicability for environmental water samples, HF-LPME was compared with a dispersive liquid–liquid microextraction (DLLME) method developed in our previous work and with a conventional solid-phase extraction method. Comparable LODs were achieved: 0.0020–0.16 μg/L for HF-LPME, 0.0020–0.090 μg/L for SPE, and 0.040–0.75 μg/L for DLLME, while repeatability with RSD below ±20% was acceptable for all three methods. The accuracy was highest for SPE, followed by HF-LPME and DLLME. The methods were also compared in terms of environmental impact using the tools Analytical Eco-Scale and GAPI, with HF-LPME giving the best results, followed by DLLME and SPE. Finally, polar benzotriazoles were determined in Slovenian wastewaters at concentrations up to 11.6 μg/L in the influent and up to 9.1 μg/L in the effluent wastewater, but they were generally not detected in samples of river water or groundwater.

Extraction and Separation of Chiral Amino Acids for Life Detection on Ocean Worlds Without Using Organic Solvents or Derivatization.

In situ instrumentation that can detect amino acids at parts-per-billion concentration levels and distinguish an enantiomeric excess of either d- or l-amino acids is vital for future robotic life-detection missions to promising targets in our solar system. In this article, a novel chiral amino acid analysis method is described, which reduces the risk of organic contamination and spurious signals from by-products by avoiding organic solvents and organic additives. Online solid-phase extraction, chiral liquid chromatography, and mass spectrometry were used for automated analysis of amino acids from solid and aqueous environmental samples. Carbonated water (pH ∼3, ∼5 wt % CO2 achieved at 6 MPa) was used as the extraction solvent for solid samples at 150°C and as the mobile phase at ambient temperature for chiral chromatographic separation. Of 18 enantiomeric amino acids, 5 enantiomeric pairs were separated with a chromatographic resolution >1.5 and 12 pairs with a resolution >0.7. The median lower limit of detection of amino acids was 2.5 μg/L, with the lowest experimentally verified as low as 0.25 μg/L. Samples from a geyser site (Great Fountain Geyser) and a geothermal spring site (Lemon Spring) in Yellowstone National Park were analyzed to demonstrate the viability of the method for future in situ missions to Ocean Worlds.

Dual-channel responsive fluorescent sensor for the logic-controlled detection and bioimaging of Zn2+ and Hg2+

The fluorescence sensing of specific cationic species is necessary and crucial due to their numerous potential effects on living organisms and the environment. In the present investigation, an efficient dual-channel responsive novel probe based rhodamine 6G condensed isophorone moiety (RHI) was designed and synthesized for sensitive, rapid and specific sensing of metal ions. RHI enabled selective and quick recognition of Zn2+ and/or Hg2+ in the presence of other tested metal ions in EtOH/H2O (8/2, v/v). It demonstrated remarkable red for Zn2+ or yellow emission enhancement for Hg2+ and good photochromism. Addition of S2− to a solution of RHI-M2+ reversed the process, followed by quenching emission, enabling reversible use of RHI. It was able to detect the levels of Zn2+ and Hg2+ within the limit of detection of 82.2 nM and 1.13 μM, respectively. Measurements of mineral and tap water samples prove the potential of the probe RHI for the detection of Zn2+ and Hg2+ ions in environmental aqueous samples. Dual-channel fluorescence response of RHI for Zn2+ and Hg2+ ensured a chance to apply them for build simple or complex molecular logic circuits. Moreover, it could easily visualize Zn2+ or Hg2+ in DDL-1 cells in bioimaging experiments.

Chitosan-based ion-imprinted polymer for selective extraction of Zn(II) in aqueous samples

ABSTRACT In this study, a new strategy for novel chitosan-based ion-imprinted polymer (IIP) preparation was adopted for selective separation and recovery of Zn(II) ions from aqueous environmental samples using batch extraction experiments. The Zn(II) ion-imprinted polymer was prepared by precipitation copolymerisation of methacrylamide and 2,2- azobisisobutyronitrile along with Zn(II) ions and toluene as a functional complexing monomer, initiator, template ion, and porogenic solvent, respectively, in the presence of chitosan. The ethylene glycol dimethacrylate and tetraethyl orthosilicate were used as cross-linking agents. The prepared Zn(II) ion-imprinted polymer was characterised by Fourier transform infrared spectroscopy, field emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric analysis, and inductively coupled plasma-optical emission spectroscopy to determine the structural and functional IIP variations before and after Zn(II) adsorption. Characterisation results suggested the formation of Zn(II) ion-imprinted polymer with excellent thermal stability and also have the potential for selective Zn(II) extraction. Further, the Zn(II) sorption using IIP sorbent was also evaluated as a function of pH, IIP sorbent dosages, Zn(II) ion concentration, sorption time, and IIP sorbent reusability. The Zn(II) sorption equilibrium was studied using various isotherm and kinetic models, and the result suggested that the Langmuir and pseudo-second-order model as the best to explain the sorption process. Sorption capacity was calculated using Langmuir isotherm linear equation and its value was found to be 3.06 mg/g. The method detection limit (MDL) and limit of quantification (LOQ) of sorbent were calculated as 0.1 and 0.3 mg/L, respectively. Finally, the developed sorbent Zn(II) IIP was found to be effective in the selective extraction of Zn(II) from the tap and river water samples.