Natural Water Samples Research Articles

Fe3O4-Ti3AlC2 max phase impregnated with 2-(5-Bromo-2-pyridylazo-5-(diethylamino) phenol for magnetic solid phase extraction of Cadmium, lead and cobalt from water and food samples

In this work, we report the preparation of Fe3O4-Ti3AlC2 max phase impregnated with 2-(5-Bromo-2-pyridylazo-5-(diethylamino) phenol) and its implementation for the extraction of cadmium, lead and cobalt from water and food samples. Blended Fe3O4-Ti3AlC2 max phase impregnated with 2-(5-Bromo-2-pyridylazo-5-(diethylamino) phenol) was characterized using different instrumental techniques like scanning electron microscopy (SEM), surface area analyser (SAA), energy dispersive X-rays (EDX), Fourier transform infrared spectroscopy (FT-IR) and X-rays diffraction (XRD) for surface morphology, surface region, elemental composition, functional group and crystallinity, respectively. Factors that impact the % recoveries of analyte i.e pH, sample volume, vortex time, desorption condition and matrix impact were optimized. Analytical parameters like limit of detection (LOD) (Cd: 0.093 µg/L, Pb: 0.297 µg/L, Co: 0.223 µg/L), limit of quantifications (LOQ) (Cd: 0.310 µg/L, Pb: 0.992 µg/L, Co: 0.744 µg/L) preconcentration factors (PF) (Cd = Pb = Co: 40), enrichment factors (EF) (Cd: 39.8, Pb: 39, Co: 40) and relative standard deviation (RSD) (Cd: 3.8, Pb: 5.98, Co: 4.0) were determined under optimized trial conditions. The proposed strategy was tested using certified reference materials like TMDA-64.3 natural water and tobacco leaves (INCT-OBTL-5) for trace metal analysis. The developed strategy was also applied effectively to natural water samples and food samples using the standard addition method with good recovery results.

Chromoionophore decorated renewable solid-state polymer monolithic naked eye sensor for the selective sensing and recovery of ultra-trace toxic cadmium ions in aqueous environment

In the present study, we report an intelligent solid-state chemosensor by embedding a chromo-ionophoric probe (MQP), i.e., (Z)− 4-methoxy-2-(quinolin-8-yldiazenyl)phenol) onto a bimodal meso-/macro-porous monolithic polymer template for the target-specific sensing of toxic cadmium(II) ions. The MQP probe anchored polymeric sensor material imposes rapid detection kinetics upon interaction with cadmium ions through concentration proportionate visual colour transitions from pale pink to red wine. The unique structural and surface properties of sensor material for the target-specific ion-sensing amidst matrix constituents have been analyzed using p-XRD, TEM-SAED, SEM-EDAX, XPS, FT-IR, and BET/BJH analysis. The analytical sensing performance of the MQP sensor material has been studied by optimizing various physicochemical parameters. For the efficient detection of ultra-trace Cd(II) ions, a solution pH range of 7.5–8.5, solution temperature of ≥ 30 °C, response kinetics of ≥ 25 s, and a linear response range of 0–300 µg/L, with excellent ion-selectivity/-sensitivity. The limit of detection and quantification for the MQP sensor material for Cd(II) ion-sensing is 0.32 and 1.10 µg/L, respectively. The proposed solid-state naked-eye sensor adopts a simple and low-cost fabrication procedure for continuously monitoring natural and industrial water samples. The sensor is reusable for up to eleven repeated cycles and exhibits excellent data reliability/reproducibility for the quantitative detection and recovery of ultra-trace Cd(II) ions.

The first fully optimized and validated SPE-LC-MS/MS method for determination of the new-generation neonicotinoids in surface water samples

Widespread use of the new generation neonicotinoids (NQs) results in their constant inflow to water bodies. Both their persistence in waters and mechanism of action similar to older compounds already banned in the EU raise concerns about potential ecotoxicological effects. Information about presence of the new NQs in the aquatic environment is still sparse, and the consequences for aquatic organisms remain mostly unknown, due to the lack of sensitive and selective analytical tools. Therefore, a method utilizing solid-phase extraction and liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) has been developed and optimized, enabling the monitoring of EU-approved NQs: acetamiprid (ACT), sulfoxaflor (SFX) and flupyradifurone (FLU), and common NQ metabolite 6-chloronicotinoic acid (6-CNA) in surface waters. To optimize their extraction from natural water samples, the response surface methodology (RSM) was used. An increase in pH value favored higher absolute recoveries (AR) of ACT, SFX and FLU, while the opposite effect was observed for 6-CNA. Increasing water sample volume had adverse effect on the extraction of all compounds. The optimal conditions for simultaneous extraction of all compounds included the use of Oasis HLB sorbent, 200 mL of a water sample at pH of 4.6, and application of 0.3% HCOOH in acetonitrile as an eluent, allowing to obtain AR values above 80% in most cases. Further increase in pH value had positive impact on extraction effectiveness of ACT, SFX and FLU. The method was subjected to full matrix-matched validation and was proven to be fully reliable for the analysis of ACT, SFX and FLU, while the successful isolation of 6-CNA depends on the matrix composition. Finally, the method was applied to the analysis of NQs in surface water samples, proving its sensitivity and selectivity. It can be easily adapted as a tool for trace analysis of NQs and for NQ-associated risk assessment in aquatic ecosystems.

Detection and Quantification of Antimicrobial-Resistant Cells in Aquatic Environments by Bioorthogonal Noncanonical Amino Acid Tagging.

Aquatic environments are important reservoirs of antibiotic wastes, antibiotic resistance genes, and bacteria, enabling the persistence and proliferation of antibiotic resistance in different bacterial populations. To prevent the spread of antibiotic resistance, effective approaches to detect antimicrobial susceptibility in aquatic environments are highly desired. In this work, we adopt a metabolism-based bioorthogonal noncanonical amino acid tagging (BONCAT) method to detect, visualize, and quantify active antimicrobial-resistant bacteria in water samples by exploiting the differences in bacterial metabolic responses to antibiotics. The BONCAT approach can be applied to rapidly detect bacterial resistance to multiple antibiotics within 20 min of incubation, regardless of whether they act on proteins or DNA. In addition, the combination of BONCAT with the microscope enables the intuitive characterization of antibiotic-resistant bacteria in mixed systems at single-cell resolution. Furthermore, BONCAT coupled with flow cytometry exhibits good performance in determining bacterial resistance ratios to chloramphenicol and population heterogeneity in hospital wastewater samples. In addition, this approach is also effective in detecting antibiotic-resistant bacteria in natural water samples. Therefore, such a simple, fast, and efficient BONCAT-based approach will be valuable in monitoring the increase and spread of antibiotic resistance within natural and engineered aquatic environments.

Sensitive Determination of Trace 4-Nitrophenol in Ambient Environment Using a Glassy Carbon Electrode Modified with Formamide-Converted Nitrogen-Doped Carbon Materials.

Sensing trace amounts of 4-nitrophenol (4-NP) as a harmful substance to organisms even in small quantities is of great importance. The present study includes a sensitive and selective electrochemical sensor for detecting 4-NP in natural water samples using formamide-converted nitrogen-carbon materials (shortened to f-NC) as a new material for electrode modification. The structure and morphology of the f-NC were set apart by SEM, TEM, XRD, XPS, FTIR, Raman, and the electrochemical performance of the f-NC were set apart by CV, EIS and CC. We studied the electrochemical behaviour of 4-NP on the glassy carbon electrode modified with f-NC before and after pyrolysis treatment (denoted as f-NC1/GCE and f-NC2/GCE). In 0.2 M of H2SO4 solution, the f-NC2/GCE has an apparent electrocatalytic activity to reduce 4-NP. Under the optimal conditions, the reduction peak current of 4-NP varies linearly, with its concentration in the range of 0.2 to 100 mM, and the detection limit obtained as 0.02 mM (S/N = 3). In addition, the electrochemical sensor has high selectivity, and the stability is quite good. The preparation and application of the sensor to detect 4-NP in water samples produced satisfactory results, which provides a new method for the simple, sensitive and quantitative detection of 4-NP.

A new Desmodesmus sp. from the Tibetan Yamdrok Lake.

Revegetation of exposed sub-soil, while a desirable recovery strategy, often fails due to extreme soil chemical properties, such as low organic matter and pH levels. Microalgae play a key role in maintaining water quality in the lakes and rivers on the Qinghai-Tibet plateau. Plateau microalgae have extensive application prospects in environmental purification, biotechnology, medicine and cosmetics, food industry, and renewable energy. To identify the high biomass of microalgae present in nature, microalgae with the greatest biomass were screened from natural water samples through filtration, pre-culture, and plate scribing separation. Following identification via 18S rRNA sequencing as for the Desmodesmus sp., we constructed a neighbor-joining phylogenetic tree. The novel Desmodesmus sp. from the Tibetan Yamdrok Lake were identified through polyphasic taxonomy. Simultaneously, the sequence of the experimental samples and the target species were shown different following the identification and analysis of SNP and InDel loci. The light-absorbing properties of plateau Desmodesmus sp. have been investigated previously. The characteristic absorption peak of Desmodesmus sp. on the plateau was measured at 689 nm in the visible spectrum using full wavelength scanning with a UV-Vis spectrophotometer. For Desmodesmus sp. which is prone to settling in the process of amplification culture. By monitoring the change trend of total nitrogen, total phosphorus, pH and electrical conductivity in algae solution system, we determined that the logarithmic growth phase and the best transfer window of Desmodesmus sp. were at 15-20 days. This study can provide basic research methods for the study of microalgae in high altitude areas, and lay a foundation for the later study and application of microalgae.

Cost-effective screen-printed carbon electrode biosensors for rapid detection of microcystin-LR in surface waters for early warning of harmful algal blooms.

Microcystins (MCs) are toxins produced by cyanobacteria commonly found in harmful algal blooms (HABs). Due to their toxicity to humans and other organisms, the World Health Organization (WHO) sets a guideline of 1 μg L-1 for microcystin-leucine-arginine (MC-LR) in drinking water. However, current analytical techniques for the detection of MC-LR such as liquid chromatography-mass spectrometry (LC-MS) and ELISA are costly, bulky, time-consuming, and mostly conducted in a laboratory, requiring highly trained personnel. An analytical method that can be used in the field for rapid determination is essential. In this study, an anti-MC-LR/MC-LR/cysteamine-coated screen-printed carbon electrode (SPCE) biosensor was newly developed to detect MC-LR, bioelectrochemically, in water. The functionalization of the electrode surface was confirmed with surface characterization methods. The sensor performance was evaluated by electrochemical impedance spectroscopy (EIS), obtaining a linear working range of MC-LR concentrations between 0.1 and 100 μg L-1 with a limit of detection (LOD) of 0.69 ng L-1. Natural water samples experiencing HABs were collected and analyzed using the developed biosensor, demonstrating the excellent performance of the biosensor with a relative standard deviation (RSD) of 0.65%. The interference tests showed minimal error and RSD values against other common MCs and possible coexisting ions found in water. The biosensor showed acceptable functionality with a shelf life of up to 12 weeks. Overall, the anti-MC-LR/MC-LR/cysteamine/SPCE biosensors can be an innovative solution with characteristics that allow for in situ, low-cost, and easy-to-use capabilities which are essential for developing an overarching and integrated "smart" environmental management system.

Molecular simulations of CRANADs to disclose a specific cyanide sensor in aqueous media

Chemical pollutants are the major contaminants in natural water samples and can be introduced either through natural processes or as a result of human activities. Some of the cations and anions such as cyanide, lead, mercury, and arsenic are toxic even at extremely low concentrations. The fatal effects of cyanide ions on the ecosystem have led to extensive research in the advancement of methods for rapid and specific detection of cyanide. We already reported the theoretical and experimental studies on the specific cyanide sensing capacity of the curcuminoid-BF2 complex, CRANAD-1. However, the theoretical investigation of the sensing mechanism of these types of CRANADs pointed out the key structural features which are capable of generating a better fluoroprobe for the rapid detection of cyanide in aqueous media even in trace quantities. Herein, we designed a novel selective and efficient fluorescent probe for cyanide detection based on these features. The DFT (Density Functional Theory) approach explores the significance of the probe in the quantitative detection of cyanide concentration in natural water samples. A comprehensive examination of the binding energies of the designed CRANADs in presence of various anions such as CN−, F−, Cl−, Br−, AcO−, SO42−and NO3− were carried out using the B3LYP level of density functional theory using SDD and 6-311++G** basis sets. Theλmaxabsorption values, FMO (Frontier Molecular Orbital), ESP (Electrostatic potential) plots and NBO (Natural Bond Orbital) analysis reveal the better cyanide sensing ability of the D–A–D (Donor-Acceptor–Donor) type CRANAD scaffold.

Factorial design optimization of dispersive liquid–liquid microextraction for analysis of metals in natural and drinking waters

In this work, a dispersive liquid–liquid microextraction method combined with inductively coupled plasma optical emission spectrometry was developed to extract and pre-concentrate the trace metals cadmium and lead. Variables such as extracting solvent, dispersive solvent and chelating agent were studied using a univariate design. On the other hand, parameters such as pH, volume of the extracting solvent, volume of the dispersive solvent and concentration of the chelating agent were optimized using a factorial design 24. Doehlert design was used to improve the conditions established in the factorial design. The optimized method consisted of chelating agent concentration of 0.05 % (w/v), 8000 µL of dispersive solvent (ethanol), 600 µL of extracting solvent (chlorobenzene) and a pH of 7.0. Using these conditions, it was obtained a limit of detection of 0.85 and 0.55 µg L-1, enrichment factors of 13.4 and 10 and relative standard deviation of 0.8 and 3.7 % (5 µg L-1, n = 3) for the metals Cd and Pb, respectively. The developed methodology was applied for the analysis of cadmium and lead in natural and drinking water samples.

Aniline-Naphthylamine Copolymer as the Solid Phase Microextraction (SPME) Fiber Coating for the Determination of Chlorobenzenes by Gas Chromatography – Mass Spectrometry (GC-MS)

A new solid phase microextraction fiber coating based on aniline-naphthylamine copolymer was prepared using an electrochemical approach on a wire as a robust substrate. The aniline polymer, naphthylamine polymer, and diverse ratio of the aniline-naphthylamine copolymer were synthesized and subsequently characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The results demonstrate that the aniline-naphthylamine copolymer has high porosity and a non-uniform structure compared to the unmodified polymers. The method was employed for the determination of chlorobenzenes (CBs) as model compounds for determination from water samples. The significant parameters of the sorbent morphology and extraction processes, including the type of polymer, the concentration of polymer, the electrochemical time and applied voltage, the extraction time and temperatures, and the concentration of salts, were optimized. The developed approach is sensitive, rapid, and provides suitable detection limits between 0.8 and 1.5 ng L−1. Moreover, the limit of quantification was 3–5 ng L−1 with an equilibrium time of 25 min. The linearity of the method was between 5 and 1500 ng L−1 with the correlation coefficient R2 exceeding 0.9997. The repeatability of the method was evaluated at 40 ng L−1 and relative standard deviation values were from 4 to 8% were obtained. Lastly, the developed protocol was employed to analyze natural water samples with recovery values from 96 to 101%, illustrating the absence of matrix effects.

ANALYSIS OF THE RADON CONCENTRATIONS IN NATURAL MINERAL AND TAP WATER USING LUCAS CELLS TECHNIQUE

The aims of this study were to determine the radon concentration in natural mineral and tap water and to estimate the resulting ingestion doses received by adults. Physical-chemical characteristics of water samples have also been investigated. In the last years have been an increase of water consumption of both, natural mineral and tap, many sources and producers being available on the market. Thus, the physical-chemical and radiologic parameters of water must be in compliance with the Drinking Water Directive (DWD). Thus, the study presents an assessment of the radioactivity due to 222Rn and 3H in several mineral natural water samples from the north region of Romania, but also in several tap water samples. The methods used were based on gamma spectrometry, gross alpha-beta measurements and beta spectroscopy, but also ICP-MS for chemical parameters. The results of this work showed that the geology and rock types clearly influence the water radon concentration. The radon concentration is lower in the water that passes through sedimentary rocks than that passing through granitic rocks. An important aspect of this work is to provide reliable information regarding radon and tritium concentrations. Radon concentration varied between 0.15±0.05 Bq/L and 11.35±2.97 Bq/L in the natural mineral water samples and between 0.17±0.05 Bq/L and 8.51±2.34 Bq/L in the tap water samples. An estimation of annual effective radiation dose based on the sample results was also made. Calculated values for ingestion dose due to regular consumption of water does not induce a health risk because of the intake of various radionuclides contained in the water. The maximum values being of 47.38 µSv/y. The determined values for the collected samples are below recommended reference levels, but more important aspect is that this study emphasise environmental sustainability in the investigated area.

Ion-specific bathochromic shifts: Simultaneous detection of multiple heavy metal pollutants via charge transfer interactions

An anthraimidazoledione-based colorimetric probe (1) has been developed to detect heavy metal pollutants in acetonitrile medium. Adding metal ions, such as Zn2+, Ni2+ and Co2+ induce ion-dependent redshifts in the metal-to-ligand charge transfer (MLCT) band. As a result, the almost colorless solution of1turned into green, yellow and red colors upon adding Zn2+, Ni2+, and Co2+ ions. On the other hand, the blue fluorescence of 1 is slightly quenched in the presence of Zn2+ ions, while the diminution is significant for Ni2+ ions. On the other hand, Co2+ ion results in the red-shift of emission maxima and quenching. Thus, we could observe faint cyan-colored fluorescence with Co2+ ions. The binding affinities for metal ions follow Irving–William’s order. At the same time, the colorimetric responses depend on the ionic radius, hydration enthalpy, coordination number, crystal field stabilization energies of the metal ions, etc. However, in the mixed aqueous environment, the ratiometric response was noticed only with Co2+ ions. Along with ratiometric color change, additions of metal ions result in an increase in both anodic and cathodic peak current along with shifts in the redox potential values. Further, the presence of residual Co2+ was determined in natural water samples.

Double Immunochromatographic Test System for Sensitive Detection of Phycotoxins Domoic Acid and Okadaic Acid in Seawater and Seafood.

In this investigation, a double immunochromatographic analysis (ICA) of two relevant phycotoxins, domoic acid (DA) and okadaic acid (OA), was developed for the first time. The ICA was performed in the indirect competitive format using gold nanoparticles conjugated with anti-species antibodies. Under optimal conditions, the instrumental detection limits/cutoffs for simultaneous detection of DA and OA were 1.2/100 and 0.1/2.5 ng/mL, respectively. The time of the assay was 18 min. The ICA was applied to test seawater and a large panel of seafood, including mussels, tiger shrimps, octopuses, whelks, crabs, and scallops. The proposed simple sample preparation method for seafood takes only 20 min. For seawater, a dilution by buffer was implemented. The assay recoveries varied from 80.8% to 124.5%. The competitive potential of the proposed technique as a tool to control natural water and seafood samples is determined by its simplicity, rapidity, and sensitivity.

Easy detection of Prorocentrum donghaiense by polymerase chain reaction-nucleic acid chromatography strip.

In recent years, Prorocentrum donghaiense, as a dominant species, has ranked first in terms of cumulative number and area of algal blooms in the East China Sea. In this study, the D1-D2 region of the large ribosomal subunit of P. donghaiense was used as the target gene, and specific primers DH-FP/DH-RP were designed according to the species-specific region of the target gene. An easy, sensitive and visual detection method refered to as polymerase chain reaction-nucleic acid chromatography strip (PCR-NACS) was established for P. donghaiense. The optimized parameters of the PCR amplification system are as follows: primer concentration, 0.15μM; annealing temperature, 62°C; and Mg2+ concentration, 1.5mM. The specificity test showed that PCR-NACS was exlusively specific for the detection of the target algae. The sensitivity test show that the lowest detection limit (LDL) of PCR-NACS was 2.7 × 10-2ng·μL-1 for genomic DNA and 3.58 × 102 copies·μL-1 for plasmid DNA, respectively. The tests using both genomic DNA and plasmid DNA as templates showed that the sensitivity of PCR-NACS was 10 times higher than that of ordinary PCR. The stability test showed that the interfering algal species did not affect the detection of the target algae by PCR-NACS. In addition, the test with simulated natural samples containing target algae showed that the LDL of PCR-NACS could reach 1.27 × 101 cells·mL-1. In summary, the PCR-NACS established in this study may provide a new method for easy identification of P. donghaiense in natural water samples.

Green synthesis of bimetallic nanocomposite: Efficient use of nanocomposite in the removal of phenol and n-(n-Propyl) thiourea by photo-Fenton-like process

The contamination of water bodies with emerging and persistent water contaminants, viz., phenol and n-(n-propyl) thiourea (NNPT) is a severe environmental and health concern. This study aims to obtain the novel bimetallic heterogeneous nanocatalyst supported with natural bentonite using a facile greener route. The in situ nanoparticles, i.e., Fe0 and Ag0, were obtained utilizing natural phytochemicals from leaf extracts of P. guajava. The XPS and XRD analyses inferred the presence of Ag0(NPs) and Fe0(NPs) in the composite material. Moreover, the bandgap energy of nanocomposite material (Ben@(Fe0+Ag0)) was 2.25 eV compared to the pristine bentonite of 3.25 eV. Further, the nanocatalyst was efficiently employed in the photo-Fenton-like process to eliminate of phenol and NNPT in an aqueous medium. The degradation efficiency of the catalyst for targeted pollutants was found to be 73% (for phenol) and 95% (for NNPT) in the photo-Fenton-like process for 2 h of UV-A illumination. Similarly, a significant efficiency (Ca. 60% for phenol and Ca. 90% for NNPT) was achieved utilizing the LED (Visible) light illumination in a similar photo-Fenton-like process. The degradation of these two pollutants has predominantly proceeded through the •OH radicals. The photo-Fenton-like process mineralized these two pollutants significantly. Several parameters optimized the Fenton-like process, including pH, catalyst dose, and H2O2 concentration. The repeated photo-Fenton-like processes for 4 consecutive cycles showed an insignificant decrease in the efficiency of nanocatalyst, at least in the elimination of these two contaminants. The process was further employed to eliminate phenol and NNPT in the natural water samples spiked with known concentrations of these pollutants. The promising approach is excellent for the removal of recalcitrant environmental pollutants.

Investigation of natural colloidal particles contained metals in lake water by single particle inductively coupled plasma mass spectrometry

ABSTRACT The existence of inorganic elements in natural water is heterogeneous due to the suspended micro colloidal and nanoparticles. In this work, the signals of Fe, Cu, Cd, Pb content in natural water samples collected from a city lake were examined using the single-particle inductively coupled plasma mass spectrometry (ICP-MS) under the time resolved detection mode. Total numbers, data distributions and central values of the detected signals were obtained based on statistical analysis using the Excel and the Origin software. Both fractionation filtration (0.22, 0.45 and 3.0 µm membranes) and centrifugation (2000, 4000, 6000 and 8000 rpm rotating speed) have a significant effect on the detection of metals coexisted in the natural colloidal particles (NCPs) in water. Notable number of single-particle signals still presents in the lake water samples even after the pretreatment of 0.22 µm filtration or 8000 rpm centrifugation, which reveals the ubiquitous existence of micro aggregates or colloids in natural water. Sampling with online dilution is proved to be a direct, simple and effective method for the implementation of time resolved analysis of metallic micro NCPs in lake water by ICP-MS, especially for elements with high dissolved concentration. The results enhance the knowledge of how-to evaluation of the quantity and chemical stability of metal-containing aggregates, colloids and nanoparticles that may exist in natural water.

Assessing organic fouling of ultrafiltration membranes using partition coefficients of dissolved organic matter in aqueous two-phase systems

Organic fouling caused by dissolved organic matter (DOM) is a critical challenge for membrane technologies. In this study, prediction models for the fouling of commercial polyether sulfone (PES) and regenerated cellulose (RC) ultrafiltration membranes by DOM were established based on the hydrophobicity of DOM. The organic fouling behavior of 40 natural water samples collected from Lake Taihu was investigated. The fouling propensity of water samples on ultrafiltration membranes was evaluated using the fouling index (FI). The hydrophobicity of DOM in water samples was quantified by its partition coefficient in an aqueous two-phase system (KATPS). The FI of water samples on RC membranes was lower than that on PES membranes due to stronger repulsive Lewis acid-base interactions, which reduced DOM-membrane interactions. A significant positive correlation was found between KATPS and FI, suggesting the important role of DOM hydrophobicity in the organic fouling of ultrafiltration membranes. FI prediction models using KATPS as the variable were established using a training group containing 20 water samples for PES and RC membranes, respectively. The resulting models were then validated using the additional 20 water samples, which suggested good prediction power (RMSE = 1.65). The pH effect on the organic fouling can be adequately predicted by the same model with KATPS values measured at given pH. The results suggest that KATPS can be used as a convenient index for assessing the initial organic fouling of ultrafiltration membranes by freshwater DOM.

“Caught in the Act” @ disruption of A-ET-E process in the recognition of F− by a lamellar EuIII-MOF in heterogeneous manner with logic gate construction: From protagonist idea to implementation world

Development of cost-effective and reliable fluoride sensor for assessing water quality of natural water samples is of immense importance in developing countries as they can provide an easy platform for safeguarding human health. These sensors should be as simple as possible to be fabricated locally by layman. In this context, EuIII-based MOFs provide trustable platform with bright luminescence in the visible region due to their absorbance-energy transfer-emission (A-ET-E) process. Herein the designed synthesis of a 2D porous coordination polymer, Eu@CMERI, has been carried out following a solvothermal reaction route. The compound shows selective “turn-off“ sensing of fluoride in heterogeneous manner from purely aqueous phase and other biological matrices with a detection limit of 28.4 ppb and it carries enormous importance for drinking water analysis under internal regulations. Prohibition of A-ET-E cycle of the EuIII-MOF is proposed to be the prime reason for fluorescence quenching upon interaction with F−. DFT studies also revealed that lowest △EHOMO-LUMO and highest chemical potential value (μ) of F− are the driving forces for selectivity of EuIII-MOF towards the targeted anion. The high stability of the porous frameworks along with its interesting sensing features, including fast response and wide linear detection range etc. instigated us not to restrict the chemistry of EuIII-MOFs at protagonist idea rather to explore its application to real-world analysis. Based on the fluorescence signal exhibited by the targeted analyte, an integrated AND-OR logic gate has also been fabricated which depicts its applicability in molecular electronics. In view of the modular design principle of our polymeric probe, the proposed strategy could open a new horizon to construct powerful sensing materials for ultrafast detection of other important pollutants in the domain of supramolecular chemistry in coming days.

An Optical Fiber Sensor for Uranium Detection in Water.

An optical sensor for uranyl has been prepared based on a gold-plated D-shaped plastic optical fiber (POF) combined with a receptor consisting of a bifunctional synthetic molecule, 11-mercaptoundecylphosphonic acid (MUPA), with a phosphonic group for complexing the considered ion, and a sulfide moiety through which the molecule is fixed at the gold resonant surface as a molecular layer in an easy and reproducible way. The sensor is characterized by evaluating the response in function of the uranyl concentration in aqueous solutions of different compositions and real-life samples, such as tap water and seawater. The mechanism of the uranyl/MUPA interaction was investigated. Two different kinds of interactions of uranyl with the MUPA layer on gold from water are observed: a strong one and a weak one. In the presence of competing metal ions as Ca2+ and Mg2+, only the strong interaction takes place, with a high affinity constant (around 107 M−1), while a somewhat lower constant (i.e., around 106 M−1) is obtained in the presence of Mg2+ which forms stronger complexes with MUPA than Ca2+. Due to the high affinity and the good selectivity of the recognition element MUPA, a detection limit of a few μg L−1 is reached directly in natural water samples without any time-consuming sample pretreatment, making it possible for rapid, in situ controls of uranyl by the proposed sensor.

Detection of Atrazine and Its Metabolites in Natural Water Samples Using Photonic Molecularly Imprinted Sensors.

In a previous study, photonic-based molecularly imprinted polymers (MIPs) were fabricated using atrazine (ATZ) and its metabolites, desethylatrazine (DEA) and desisopropylatrazine (DIA), as templates in separate matrices. For the purposes of monitoring the abovementioned molecules in natural waters, the effect of natural waters—featuring ionic strength and natural organic matter (NOM) on atrazine MIP—were studied in this work, and the photonic MIP was implemented for monitoring the target molecules in natural water samples collected from land in nearby farms in northeast of Columbia MO. Non-imprinted polymers (NIP) were also fabricated and applied in the experiments as a control test. In presence of NaCl, CaCl2, and NOM, MIPs presented lower responses by 26%, higher responses by 23%, and higher responses by 35%, respectively. NIPs response in terms of an increase or decrease was consistent with those of MIPs, but only for a lower percentage. MIPs response in natural waters—which were characterized for their physicochemical characteristics such as conductivity, total organic carbon content, etc.—provided a good approximation of the real concentrations obtained from the LCMS instrument; in general, they showed a good concordance, although large discrepancies occurred for some samples, which can be related to reproducibility issues in the manufacturing process or the presence of unknown interfering compounds in the real samples.