Microfluidic sensors for the detection of emerging contaminants in water: A review

In recent years, numerous emerging contaminants have been identified in surface water, groundwater, and drinking water. Developing novel sensing methods for detecting diverse emerging pollutants in water is urgently needed, as even at low concentrations, these pollutants can pose a serious threat to human health and environmental safety. Traditional testing methods are based on laboratory equipment, which is highly sensitive but complex to operate, costly, and not suitable for on-site monitoring. Microfluidic sensors offer several benefits, including rapid evaluation, minimal sample usage, accurate liquid manipulation, compact size, automation, and in-situ detection capabilities. They provide promising and efficient analytical tools for high-performance sensing platforms in monitoring emerging contaminants in water. In this paper, recent research advances in microfluidic sensors for the detection of emerging contaminants in water are reviewed. Initially, a concise overview is provided about the various substrate materials, corresponding microfabrication techniques, different driving forces, and commonly used detection techniques for microfluidic devices. Subsequently, a comprehensive analysis is conducted on microfluidic detection methods for endocrine-disrupting chemicals, pharmaceuticals and personal care products, microplastics, and perfluorinated compounds. Finally, the prospects and future challenges of microfluidic sensors in this field are discussed.

Machine learning-assisted chromium speciation using a single-well ratiometric fluorescent nanoprobe

Chromium is widely recognized as a significant pollutant discharged into the environment by various industrial activities. The toxicity of this element is dependent on its oxidation state, making speciation analysis crucial for monitoring the quality of environmental water and assessing the potential risks associated with industrial waste. This study introduces a single-well fluorometric sensor that utilizes orange emissive thioglycolic acid stabilized CdTe quantum dots (TGA-QDs) and blue emissive carbon dots (CDs) to detect and differentiate between various chromium species, such as Cr (III) and Cr (VI) (i.e., CrO42- and Cr2O72-). The variations of fluorescence spectra of the proposed probe upon chromium species addition were analyzed using machine learning techniques such as linear discriminant analysis and partial least squares regression as a classification and multivariate calibration technique, respectively. Linear discriminant analysis (LDA) demonstrated exceptional accuracy in differentiating single-component and bicomponent samples. Additionally, the findings from the partial least squares regression (PLSR) showed that the sensor created has strong linearity within the 1.0-100.0, 1.0-100.0, and 0.1-15 μM range for Cr2O72-, CrO42-, and Cr3+, respectively. Furthermore, appropriate detection limits were successfully achieved, which were 2.6, 2.9, and 0.7 μM for Cr2O72-, CrO42-, and Cr3+, respectively. Ultimately, the successful capability of the sensing platform in the identification and quantification of chromium species in environmental water samples provides innovative insights into general speciation analytics.

Coumarin Linked Cyanine Dye for the Selective Detection of Cyanide Ion in Environmental Water Sample

A benzoxazole-coumarin-based probe BOC, was synthesized and validated for its anion sensing ability and found to be effective in recognizing cyanide ions. Upon addition of cyanide, a spontaneous color change was observed that was visible to the naked eye. The sensitization process takes place with nucleophilic addition, and the cyanide ion added to the probe disrupts the intra molecular charge transfer transition (ICT) between the donor and acceptor units, causing the pink colored probe to become yellow. Ultraviolet and fluorescence methods were applied to measure the detection limits of probes with added cyanide ions, which were found to be 3.47 µM and 2.48 nM. The stoichiometry of the probe with the cyanide ion was determined by the Job's method, NMR titration, and mass spectrometry and was found to be in a 1:1 ratio. The results obtained from the visual and UV-visible spectral studies are justified by theoretical calculations. The cyanide-loaded probe induced visual changes, which enabled the development of a test strip for field application, and the prepared strip can be used to detect the ppm level of cyanide in water samples. The developed probe, BOC, can be used to detect cyanide ions in various water samples.

Zinc nitride quantum dots as an efficient probe for simultaneous fluorescence detection of Cu2+ and Mn2+ ions in water samples

The exceptional ascending heights of graphene (carbon) and boron nitride nanostructures have invited scientists to explore metal nitride nanomaterials. Herein, Zn3N2 quantum dots (QDs) were prepared via a simple hydrothermal route from the reaction between zinc nitrate hexahydrate and ammonia solution that possess efficient strength towards sensing applications of metal ions (Cu2+ and Mn2+). The as-prepared Zn3N2 QDs show bright fluorescence, displaying an emission peak at 408 nm upon excitation at 320 nm, with a quantum yield (QY) of 29.56%. It was noticed that the fluorescence intensity of Zn3N2 QDs linearly decreases with the independent addition of Cu2+ and Mn2+ ions, displaying good linearity in the ranges 2.5-50 µM and 0.05-5 µM with detection limits of 21.77 nM and of 63.82 nM for Cu2+ and Mn2+ ions, respectively. The probe was successfully tested for quantifying Cu2+ and Mn2+ in real samples including river, canal, and tap water, providing good recoveries with a relative standard deviation  < 2%. Furthermore, the masking proposition can successfully eliminate the interference if the two metal ions exist together. It was found that thiourea is efficiently able to mask Cu2+ and selectively quenches Mn2+, and L-cysteine is able to halt the quenching potential of Mn2+ and is selectively able to sense Cu2+. The Zn3N2 QDs provide a simple way for the simultaneous detection of both Cu2+ and Mn2+ ions in environmental samples at low sample preparations requirements.

Summary recommendations on "Analytical methods for substances in the Watch List under the Water Framework Directive"

The Watch List (WL) is a monitoring program under the European Water Framework Directive (WFD) to obtain high-quality Union-wide monitoring data on potential water pollutants for which scarce monitoring data or data of insufficient quality are available. The main purpose of the WL data collection is to determine if the substances pose a risk to the aquatic environment at EU level and subsequently to decide whether a threshold, the Environmental Quality Standards (EQS) should be set for them and, potentially to be listed as priority substance in the WFD. The first WL was established in 2015 and contained 10 individual or groups of substances while the 4th WL was launched in 2022. The results of monitoring the substances of the first WL showed that some countries had difficulties to reach an analytical Limit of Quantification (LOQ) below or equal to the Predicted No-Effect Concentrations (PNEC) or EQS. The Joint Research Centre (JRC) of the European Commission (EC) organised a series of workshops to support the EU Member States (MS) and their activities under the WFD. Sharing the knowledge among the Member States on the analytical methods is important to deliver good data quality. The outcome and the discussion engaged with the experts are described in this paper, and in addition a literature review of the most important publications on the analysis of 17-alpha-ethinylestradiol (EE2), amoxicillin, ciprofloxacin, metaflumizone, fipronil, metformin, and guanylurea from the last years is presented.

A strategy for As(III) determination based on ultrafine gold nanoparticles decorated on magnetic graphene oxide

In this work, a new dendrimer modified magnetic graphene oxide (GO) was used as a substrate for electrodeposition of Au nanoparticles. The modified magnetic electrode was employed for sensitive measuring of As(III) ion as a well-established human carcinogen. The prepared electrochemical device exhibits excellent activity towards As(III) detection using the square wave anodic stripping voltammetry (SWASV) protocol. At optimum conditions (deposition potential at -0.5 V for 100 s in 0.1 M acetate buffer with pH 5.0), a linear range from 1.0 to 125.0 μgL-1 with a low detection limit (calculated by S/N = 3) of 0.47 μg L-1 was obtained. In addition to the simplicity and sensitivity of the proposed sensor, its high selectivity against some major interfering agents, such as Cu(II) and Hg(II) makes it an appreciable sensing tool for the screening of As(III). In addition, the sensor revealed satisfactory results for detection of As(III) in different water samples, and the accuracy of obtained data were confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) setup. Accounting for the high sensitivity, remarkable selectivity and good reproducibility, the established electrochemical strategy has great potential for analysis of As(III) in environmental matrices.

Assessing the pollution level of a subtropical lake by using a novel hydrogen sulfide fluorescence technology

Hydrogen sulfide (H₂S) is an important environmental toxin with bi-directional biological effects on organisms. In natural waters, H₂S complexes with heavy metal ions in an anaerobic environment influence heavy metals' bioavailability and induce phosphorus release and eutrophication in water columns. Traditional detection techniques, such as colorimetric, electrochemical, and chromatographic, cannot simultaneously detect H₂S and pollution assessment of subtropical lakes. To address these technical defects, we developed small-molecule fluorescent probes to evaluate the pollution level in natural water bodies. This method relies on the combination of the probes' response signals to raw water and the water quality index, thereby enhancing the accuracy and reliability of water quality assessments. Furthermore, this novel material has a large Stokes shift. It can detect complex levels of H₂S concentrations in natural water bodies by correlating the degree of contamination and fluorescence signals. The development of this visual research tool for detecting environmental H₂S levels in natural water bodies is expected to have meaningful, practical applications.

The covalent organic framework based nylon membrane extraction coupled with UHPLC-MS/MS for highly efficiency determination of hexabromocyclododecanes in environmental water

Hexabromocyclododecanes (HBCDs) have given their adverse effects on environment and human health, and highly sensitive analysis of HBCDs in water is urgent. In this study, a new method for the determination of trace HBCDs in water was established by covalent organic framework (COF) based nylon membrane extraction (ME) coupled with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The COF had been self-assembled onto the nylon membrane in a gentle strategy to fabricate COF nylon membrane. Several important ME parameters including the dosage of COF, pH, eluent condition and salinity were systematically investigated. The limits of detection and quantification were 0.011-0.014 and 0.038-0.047 ng/L for three HBCDs, respectively. The linear ranges were from 0.04 to 20 ng/L, and the relative standard deviations were 5.7-17.8 % (intra-day) and 5.2-14.1 % (inter-day). In addition, density functional theory (DFT) calculations on adsorption energy proved that the introduction of halogen bond (XB) made a key contribution to high extraction efficiency and excellent selectivity of COF nylon membrane for HBCDs. The 500 mL of samples, including tap water and reservoir water, could be extracted only in 23 min. The established method presented highly sensitive for ultra-trace analysis of HBCDs in environmental water.

Design and synthesis of nickel-doped cobalt molybdate microrods: An effective electrocatalyst for the determination of antibiotic drug ronidazole

Ronidazole (RDZ) is a veterinary antibiotic drug that has been used in animal husbandry as feed. However, improper disposal and illegal use of pharmaceuticals have severely polluted water resources. Doping/substitution of metal ions is an effective strategy to change the material's crystal phase, morphology, and electrocatalytic activity. In this work, nickel (Ni²⁺)-doped cobalt molybdate microrods (NCMO MRs) were prepared for the electrochemical detection of RDZ. The catalyst was prepared by reflux method followed by calcination at 500 °C. The prepared catalyst was confirmed by various spectroscopic and microscopic analyses. XRD and Raman spectroscopy demonstrated that the phase transition from β-CoMoO₄ to α-CoMoO₄ was achieved by Ni²⁺ doping. The SEM analysis showed that cobalt molybdate (CMO) microrods were self-assembled during Ni²⁺ doping and formed an urchin-like structure, and the average diameter of the MRs was ±50 nm. The electrocatalytic activity of the catalysts was analyzed using the CV technique. The NCMO MRs/GCE exhibited the higher current response than the pristine CMO. The electron transfer coefficient (α = 0.56) and heterogeneous rate constant (ks = 0.32 s^-1) of NCMO MRs/GCE were evaluated by kinetic studies. In addition, the diffusion coefficient of RDZ was determined to be 2.32 × 10^-5 cm²/s. Moreover, NCMO MRs/GCE exhibits a low detection limit for RDZ (15 nM) as well as a higher sensitivity (1.57 μA μM^-1 cm^-2). The fabricated RDZ sensor was successfully applied to analysis of lake and tap water samples. Based on the results, we believe that the as-prepared NCMO MRs/GCE is a viable electrode material for RDZ sensors in environmental monitoring.

Characterizing spatiotemporal variations of polycyclic aromatic hydrocarbons in Taihu Lake, China

In this study, we analyzed the concentration distributions of 20 polycyclic aromatic hydrocarbons (PAHs) in 41 water samples which were collected from the northern part of Taihu Lake during 4 field campaigns (201511, 201606, 201702 and 201709). The concentrations were determined with GC-MS, and their spatial and seasonal distribution characteristics were interpreted. The results show that 2-ring PAHs present considerably higher concentrations in warm seasons than cold seasons, but the concentrations of the other higher-ring PAHs are rather stable in warm and cold seasons. The distribution patterns of these PAHs might be mainly attributed to ambient temperature effects on the PAH solubility in the water body. Meanwhile, the spatial distributions of the PAH concentrations in cold seasons were rather various in the sampling area, while the distributions in the warm seasons were homogeneous. The different distributions could result from the water recharge from the Yangtze River during cold seasons, which diluted PAH concentrations in the northeastern part of the lake. Furthermore, via literature review on PAH concentrations in water body, PAHs are in a wide range of levels and their patterns are different among the studies, which should be more effected by local factors instead of general PAH properties. The results from this study also present special characteristics of PAHs in Taihu Lake, which exhibit more insight on PAHs existence in water bodies.

A benzothiazole-based fluorescent and colorimetric probe for the detection of ClO- and its application to zebrafish and water sample

A benzothiazole-based fluorescent and colorimetric chemosensor BZD ((E)-2-(benzo[d]thiazol-2-yl)-5-((4-(diethylamino)-2-hydroxybenzylidene)amino)phenol) was applied for detecting ClO^-. BZD showed fluorescence quenching and color variation for ClO^- via oxidative reaction between ClO^- and the imine bond. It could effectively detect ClO^- over various competitive analytes. Detection limit for ClO^- was calculated to be 1.74 μM by fluorescent method and 16.44 μM by colorimetric one, respectively. Additionally, BZD could be utilized for sensing ClO^- in zebrafish, real water sample and paper strip. The photophysical characteristics and sensing mechanism of BZD to ClO^- were studied by fluorescent and UV-visible spectroscopy, NMR titration, and ESI-mass spectrometry.

Immunoassay technology: Research progress in microcystin-LR detection in water samples

Increasing global warming and eutrophication have led to frequent outbreaks of cyanobacteria blooms in freshwater. Cyanobacteria blooms cause the death of aquatic and terrestrial organisms and have attracted considerable attention since the 19th century. Microcystin-LR (MC-LR) is one of the most typical cyanobacterial toxins. Therefore, the fast, sensitive, and accurate determination of MC-LR plays an important role in the health of humans and animals. Immunoassay refers to a method that uses the principle of immunology to determine the content of the tested substance in a sample using the tested substance as an antigen or antibody. In analytical applications, the immunoassay technology could use the specific recognition of antibodies for MC-LR detection. In this review, we firstly highlight the immunoassay detection of MC-LR over the past two decades, including classical enzyme-link immunosorbent assay (ELISA), modern immunoassay with optical signal, and modern immunoassay with electrical signal. Among these detection methods, the water environment was used as the main detection system. The advantages and disadvantages of the different detection methods were compared and analyzed, and the principles and applications of immunoassays in water samples were elaborated. Furthermore, the current challenges and developmental trends in immunoassay were systematically introduced to enhance MC-LR detection performance, and some critical points were given to deal with current challenges. This review provides novel insight into MC-LR detection based on immunoassay method.

Metabarcoding of the phytotelmata of Pseudalcantarea grandis (Bromeliaceae) from an arid zone

BACKGROUND

Pseudalcantarea grandis (Schltdl.) Pinzón & Barfuss is a tank bromeliad that grows on cliffs in the southernmost portion of the Chihuahuan desert. Phytotelmata are water bodies formed by plants that function as micro-ecosystems where bacteria, algae, protists, insects, fungi, and some vertebrates can develop. We hypothesized that the bacterial diversity contained in the phytotelma formed in a bromeliad from an arid zone would differ in sites with and without surrounding vegetation. Our study aimed to characterize the bacterial composition and putative metabolic functions in P. grandis phytotelmata collected in vegetated and non-vegetated sites.

METHODS

Water from 10 individuals was sampled. Five individuals had abundant surrounding vegetation, and five had little or no vegetation. We extracted DNA and amplified seven hypervariable regions of the 16S gene (V2, V4, V8, V3-6, 7-9). Metabarcoding sequencing was performed on the Ion Torrent PGM platform. Taxonomic identity was assigned by the binning reads and coverage between hit and query from the reference database of at least 90%. Putative metabolic functions of the bacterial families were assigned mainly using the FAPROTAX database. The dominance patterns in each site were visualized with rank/abundance curves using the number of Operational Taxonomic Units (OTUs) per family. A percentage similarity analysis (SIMPER) was used to estimate dissimilarity between the sites. Relationships among bacterial families (identified by the dominance analysis and SIMPER), sites, and their respective putative functions were analyzed with shade plots.

RESULTS

A total of 1.5 million useful bacterial sequences were obtained. Sequences were clustered into OTUs, and taxonomic assignment was conducted using BLAST in the Greengenes databases. Bacterial diversity was 23 phyla, 52 classes, 98 orders, 218 families, and 297 genera. Proteobacteria (37%), Actinobacteria (19%), and Firmicutes (15%) comprised the highest percentage (71%). There was a 68.3% similarity between the two sites at family level, with 149 families shared. Aerobic chemoheterotrophy and fermentation were the main metabolic functions in both sites, followed by ureolysis, nitrate reduction, aromatic compound degradation, and nitrogen fixation. The dominant bacteria shared most of the metabolic functions between sites. Some functions were recorded for one site only and were related to families with the lowest OTUs richness. Bacterial diversity in the P. grandis tanks included dominant phyla and families present at low percentage that could be considered part of a rare biosphere. A rare biosphere can form genetic reservoirs, the local abundance of which depends on external abiotic and biotic factors, while their interactions could favor micro-ecosystem resilience and resistance.

A 2-Hydroxy-1-naphthaldehyde Schiff Base for Turn-on Fluorescence Detection of Zn2+ Based on PET Mechanism

Zinc ion is closely related to human health. Its content in human body is small, while the effect is large. However, it is not the more the better, must be in a scientific balance. Therefore, it is significant to the rapid detection of Zn²⁺ in the environment and organism. Herein, a fluorescent probe based on 2-hydroxy-1-naphthalene formaldehyde and furan-2-carbohydrazide was conveniently synthesized via Schiff base reaction. And this probe has been successfully applied to the accurate and quantitative detection of Zn²⁺ in real samples, showing turn on fluorescence, good selectivity, very low detection limit, real time response and reusability. In addition, this probe has the potential application to trace Zn²⁺ in living cells with low cytotoxicity.

A method for detecting perfluorooctanoic acid and perfluorooctane sulfonate in water samples using genetically engineered bacterial biosensor

A simple, reagent and pre-treatment (i.e. dilution, sample purification and pH adjustment) free approach based genetically engineered bacterial biosensor is developed and demonstrated for the detection of perfluorinated compounds in water samples. The bacterial biosensor was developed by integrating two genes called regulatory (defluorinase gene) and reporter gene (green fluorescence gene) through genetic engineering techniques. The as-developed bacterial biosensor was employed to detect perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in water samples upon induction of regulatory gene and expression of green fluorescence protein. The induced fluorescence emission by the biosensor was visualized using fluorescence microscopic images. The specificity of biosensor was evaluated with different types of organic pollutants such as chlorinated compounds, polyaromatic hydrocarbons and pesticides etc., in both presence and absence of PFOA and PFOS. The biosensor was employed to detect the perfluorinated compounds at nano gram level in both standard solutions and natural water samples like river water, wastewater and drinking water with an analysis time of 24 h. The detection of PFOA and PFOS by the developed-bacterial sensor is validated by liquid chromatography coupled with mass spectrometer. The developed biosensor has demonstrated a rapid and sensitive detection of PFOA and PFOS in various water samples.

A simple and efficient Solid-Phase Microextraction - Gas Chromatography - Mass Spectrometry method for the determination of fragrance materials at ultra-trace levels in water samples using multi-walled carbon nanotubes as innovative coating

The occurrence of emerging contaminants is becoming of increasing importance to assess the impact of anthropogenic activities onto the environment. The present study reports for the first time the development and validation of an efficient method for the simultaneous determination of fragrance materials in water samples based on the use of a novel multiwalled carbon nanotubes (MWCNTs)-based solid-phase microextraction coating. Helical MWCNTs were selected as adsorbent material due to their outstanding extraction performance. The multicriteria method of desirability functions allowed the optimization of the experimental conditions in terms of extraction time and extraction temperature. Validation proved the reliability of the method for the determination of the analytes at ultra-trace levels, obtaining detection limits in the 0.2-13 ng/L range, good precision, with relative standard deviations lower than 20% and recovery rates in the 80 ± 12%-111 ± 11%. Superior enrichment factors compared to commercial fibers were also calculated. Finally, applicability to real sample analysis was demonstrated.

Solidified floating organic drop microextraction (SFODME) for the simultaneous analysis of three non-steroidal anti-inflammatory drugs in aqueous samples by HPLC

In this work, a liquid-liquid microextraction methodology using solidified floating organic drop (SFODME) was combined with liquid chromatography and UV/Vis detection to determine non-steroidal anti-inflammatory drugs (NSAIDs) naproxen (NPX), diclofenac (DCF), and mefenamic acid (MFN) in tap water, surface water, and seawater samples. Parameters that can influence the efficiency of the process were evaluated, such as the type and volume of the extractor and dispersive solvents, effect of pH, agitation type, and ionic strength. The optimized method showed low detection limits (0.09 to 0.25 μg L^-1), satisfactory recovery rates (90 to 116%), and enrichment factors in the range between 149 and 199. SFODME showed simplicity, low cost, speed, and high concentration capacity of the analytes under study. Its use in real samples did not demonstrate a matrix effect that would compromise the effectiveness of the method, being possible to apply it successfully in water samples with different characteristics.

A Highly Selective Turn-on Fluorescent and Naked-eye Colourimetric Dual-channel Probe for Cyanide Anions Detection in Water Samples

A highly selective turn-on fluorescent and naked-eye colourimetric dual-channel probe for cyanide anions (CN-) has been designed and characterized. In the mixed solution (DMSO / H₂O, 9:1, v / v), only CN- could cause an increase in the UV absorption intensity and the corresponding fluorescence intensity increased, and other anions had no significant effect on the probe. After treatment with cyanide in the probe solution, the solution showed a noticeable colour change, from light yellow to purple. Moreover, a fluorescence spectrophotometer can be used to observe that the fluorescence intensity of the solution is significantly enhanced. The response of the colourimetric and fluorescent dual-channel probe to CN- was attributed to nucleophilic addition, and the mechanism was determined by ¹H NMR spectroscopy. In addition, this probe was used to detect CN- in actual water samples, including river water, drinking water, and tap water. The spiked CN- recovery rate is very high (97.2%-100.06%), and analytical precision is also very high (RSD < 2%), which shows its feasibility and reliability for detecting cyanide ions in actual water samples.

Cationic metal-organic framework based mixed-matrix membrane for extraction of phenoxy carboxylic acid (PCA) herbicides from water samples followed by UHPLC-MS/MS determination

A novel kind of cationic metal-organic framework(MOF) based mixed-matrix membrane(MMM) namely cationic MOF-MMM was firstly designed and used for simultaneous dispersive membrane extraction(DME) of six phenoxy carboxylic acid(PCA) herbicides from water samples followed by determination using ultrahigh-performance liquid chromatography tandem mass spectrometry. The cationic MOF-MMM was synthesized by soaking the zirconium-based MOFs in a polyvinylidene fluoride(PVDF) solution and further functionalization with quaternary amine groups, viz., UiO-66-NMe₃⁺ MMM. The well-prepared UiO-66-NMe₃⁺ MMM was characterized by FT-IR, SEM, XRD, XPS, NMR and etc. Several main variables influencing the MMM based DME efficiency were investigated and optimized in detail, such as dosage ratio of MOF/PVDF, solution pH, extraction time, coexistent anions and ionic strength. Electrostatic interactions dominated adsorption mechanism between anionic PCAs and cationic UiO-66-NMe₃⁺ MMM, along with ππ conjugation and cation-π bonding, leading to better adsorption performance. Low limits of detection in the range of 0.03-0.59 ng/L and satisfactory recoveries within 80.06-117.40 % for all the PCAs are a reliable witness to demonstrate supreme sensitivity and the applicability of the developed method. By relying on the obtained results, the present work implied cationic MOF-MMM based DME can be a versatile and worthy utility for extraction of pollutants from different water samples with high throughput.

Cationic metal-organic frameworks as an efficient adsorbent for the removal of 2,4-dichlorophenoxyacetic acid from aqueous solutions

Metal-organic frameworks (MOFs) material with high surface area, good chemical stability and multi-functionality, has become an emerging adsorbent for water treatment. A novel kind of quaternary amine anionic-exchange MOFs UiO-66 namely UiO-66-NMe₃⁺ was firstly synthesized for adsorptive removal of a widely used toxic herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions. The well-prepared UiO-66-NMe₃⁺ MOFs were fully characterized, and then the main parameters affecting the adsorption process including solution pH, adsorbent dosage and coexisting anions were systematically investigated. The maximum adsorption capacity of UiO-66-NMe₃⁺ toward 2,4-D reached as high as 279 mg g^-1, much higher than that of pristine UiO-66 and aminated UiO-66. The adsorption mechanism could be attributed to the electrostatic interactions efficiently enhanced by the functionalization of quaternary amine groups, combining with the π-π conjugations between the linkers in MOFs and 2,4-D molecules, leading to the better adsorption performance of UiO-66-NMe₃⁺. Additionally, the UiO-66-NMe₃⁺ could be well regenerated by simple solvent washing and exhibited a slight decline of adsorption capacity after seven successive recycle. Furthermore, satisfactory adsorption capacity and reusability of the MOFs in environmental water samples were attained. Comparing with reported activated carbon and resin materials, the UiO-66-NMe₃⁺ MOFs possessed higher adsorption capacity and shorter equilibrium time, as well as good reusability and practicality. The developed ion-exchange functionalized MOFs provided an ideal alternative for efficient adsorptive-removal of 2,4-D from complicated aqueous environment.

Amplified electrochemical determination of UO22+ based on the cleavage of the DNAzyme and DNA-modified gold nanoparticle network structure

A superior electrochemical biosensor was designed for the determination of UO₂²⁺ in aqueous solution by integration of DNAzyme and DNA-modified gold nanoparticle (DNA-AuNP) network structure. Key features of this method include UO₂²⁺ inducing the cleavage of the DNAzyme and signal amplification of DNA-AuNP network structure. In this electrochemical method, the DNA-AuNP network structure can be effectively modified on the surface of gold electrode and then employed as an ideal signal amplification unit to generate amplified electrochemical response by inserting a large amount of electrochemically active indicator methylene blue (MB). In the presence of UO₂²⁺, the specific sites on DNA-AuNP network structure can be cleaved by UO₂²⁺, releasing the DNA-AuNP network structure with detectable reduction of electrochemical response intensity. The electrochemical response intensity is related to the concentration of UO₂²⁺. The logarithm of electrochemical response intensity and UO₂²⁺ concentration showed a wide linear range of 10~100 pM, and the detection limit reached 8.1 pM (S/N = 3). This method is successfully used for determination of UO₂²⁺ in water samples. Graphical abstract Fabricated DNAzyme network structure for enhanced electrical signal. Numerical experiments show that the current signal decreases as the concentration of UO₂²⁺ increases. It can be seen that the biosensors could be used to detect UO₂²⁺ in aqueous solution effectively.

Luminescent Sm(III) complex bearing dynamic imine bonds as a multi-responsive fluorescent sensor for F- and PO43- anions together with Zn2+ cation in water samples

We have designed and synthesized a new luminescent mononuclear samarium (III) complex Sm-2_h based on the [1 + 1] Schiff-base macrocycle H₂L2_h, derived from the cyclocondensation reaction between dialdehyde and diamine precursors, and its exact architecture is determined to be [Sm(HL2_h) (NO₃)₂]. The sensing ability of complex Sm-2_h is carefully evaluated for various common inorganic ions in solution. It is shown that complex Sm-2_h is a multi-responsive fluorimetric sensor with high selectivity for F^- and PO₄^3- anions together with Zn²⁺ cation. The sensing process is rapid within 60 s for F^- and PO₄^3- ions and 300 s for Zn²⁺ ion. Further detailed responsive investigations suggest that its sensing behavior has excellent linear relationship between the fluorescence intensity (or absorption value) and ion concentration. The limit of detection (LOD) for sensing F^-, PO₄^3- and Zn²⁺ ions are as low as 2.61 μM (2.94 μM), 1.92 μM (1.64 μM) and 5.67 μM (3.53 μM), respectively, verified by fluorimetric (or colorimetric) titration experiments. ESI mass spectra prove that these efficient detections originate from the structure collapse of sensor Sm-2_h because of the ion-induced imine bond breakage. Moreover, sensor Sm-2_h shows excellent sensing performances for F^-, PO₄^3- and Zn²⁺ ions in real water samples, and we also have developed a convenient method to detect these three ions by use of the sensor impregnated test paper strips, providing rapid and distinguishable fluorimetric color changes. Therefore, the macrocyclic Sm(III) complex Sm-2_h could be regarded as a valuable candidate for monitoring F^-, PO₄^3- and Zn²⁺ ions in practical applications.

A recyclable fluorescent probe for picric acid detection in water samples based on inner filter effect

1-Aminopyrene@ZIF-8 composite was synthesized as the fluorescent probe for picric acid (PA) based on inner filter effect. The probe displayed selective response toward PA within 10s, and a linear range was obtained from 1 to 150μM with detection limit of 0.3μM, which is much lower than the permissible level of PA in drinking water reservoir (0.5mgL^-1/2.2μM) set by China's State Environmental Protection Administration (GB3838-2002). Most importantly, the probe possessed excellent recyclability and could be recycled for at least six times. It was further applied to the detection of PA in water samples, and satisfactory recoveries were obtained in the range of 96.0-104.0%.

An application of PCR-RFLP species identification assay for environmental DNA detection

Recent advancement of environmental DNA (eDNA) methods for surveying species in aquatic ecosystems has been used for various organisms and contributed to monitoring and conservation of species and environments. Amphibians are one of the promising taxa which could be monitored efficiently by applying quantitative PCR (qPCR) or next generation sequencing to eDNA. However, the cost of eDNA detection using these approaches can be quite high and requires instruments that are not usually installed in ecology laboratories. For aiding researchers in starting eDNA studies of amphibians, especially those not specialized in molecular biology, we developed a cost efficient protocol using PCR-RFLP method. We attempted to detect eDNA of three Japanese Rana species (Rana japonica, Rana ornativentris, and Rana tagoi tagoi) in various spatial scales including an area close to the Fukushima nuclear power plant where the environment is recovering after the disaster in 2011. Our PCR-RFLP protocol was successful in detecting Rana species in static water in both laboratory and field; however, it could not detect Rana species in non-static water samples from the field. Even a more sensitive detection method (standard qPCR) was unable to detect frogs in all non-static water samples. We speculate that our new protocol is effective for frogs living in lentic habitats, but not for lotic habitats which may still require the gold standard of field observation for detection approach.

A cytosine-rich hairpin DNA loaded with silver nanoclusters as a fluorescent probe for uranium(IV) and mercury(II) ions

A dually responsive fluorescent probe for determination of U(IV) and mercury(II) ions was synthesized. The probe consists of a cytosine-rich hairpin DNA loaded with silver nanoclusters (DNA-AgNCs). The fluorescence of the AgNCs is found to be quenched by UO₂(II) at pH 5.0 and Hg(II) at pH 7.0 due to combined static and dynamic quenching. Under the optimal conditions, the green fluorescence of the DNA-AgNCs, best measured at excitation/emission wavelengths of 420/525 nm, decreases in the 4.0 to 75 pM UO₂(II) concentration range, and in the 0.3 to 8.0 nM Hg(II) concentration range. The respective detection limits are as low as 1.8 pM and 0.1 nM. The method was successfully applied to the determination of UO₂(II) and Hg(II) in (spiked) pond and taps waters and in soil extracts. Graphical abstract A label-free DNA was designed to synthesize green-fluorescent silver nanoclusters (AgNCs) and used for rapid dual detection of uranyl ions (UO₂(II)) at pH 5.0 and of mercury ions (Hg(II)) at pH 7.0 in environmental samples.

Photo-assisted electrochemical detection of bisphenol A in water samples by renewable {001}-exposed TiO2 single crystals

Bisphenol A (BPA) is a semi-persistent environmental endocrine disrupter and widely present in aqueous environments. Electrochemical detection is an effective method to monitor pollutants like BPA in aqueous environments. However, the electrode fouling from anodic polymeric products is one main barrier of electrochemical sensors for their practical applications. In this work, a renewable electrochemical sensor was rationally designed, constructed and tested for efficient BPA detection. The TiO₂ anodic material was surface-engineered by inorganic-framework molecular imprinting sites with tailored morphological shape, exposed facet and crystal structure. This electrode could be activated mainly as an electrochemical catalyst and partially as a photochemical catalyst. The developed TiO₂-based sensor exhibited a good detection reliability and cyclic stability for determining BPA in water samples, with an electrochemical signal decrease of less than 5.0% in 10-run cyclic tests. By virtue of the bi-functional properties of the tailored TiO₂ anodic material, a unique photo-assisted electrochemical sensor was further developed, in which analyte digestion and analytical signal originated mainly from anodic conversion. Such a synergistic digesting mechanism distinguishes it from the reported electro-assisted photochemical TiO₂ sensors. Our work provides a robust sensor for monitoring pollutants in aqueous environments and a new opportunity to develop renewable electrode materials with good reusability.

Analysis of trace metals in water samples using NOBIAS chelate resins by HPLC and ICP-MS

The pre-concentration of major constituents is crucial to accurate and precise determination of trace metals in water samples by inductively coupled plasma mass spectrometry (ICP-MS). In this work, NOBIAS chelate resins were used in the sample concentration for both HPLC and ICP-MS detection. 4-(2-Pyridylazo) resorcinol (PAR) was selected as a precolumn chelating reagent for this research. 520 nm wavelength was used as to minimize the peak of PAR and to reduce baseline noise for HPLC analysis. The sample pre-treatment step was achieved by enrichment and Cd(II), Co(II), Cu(II), Mn(II), Ni(IV), Pb(II), and Zn(II) were detected in the bottled water and tap water samples. The results of two detection methods of ICP-MS and HPLC were compared. Results showed that by acquiring 50-time pre-concentrates of test samples using 250 mg of the Nobias-chelate PA1 chelating resin, the metal contents could be accurately detected using both ICP-MS and HPLC. And the approach of HPLC enables the quantitative detection of bottled water and tap water at different concentrations with determination coefficient (R²) greater than 0.9990. This simple and cost-effective quantitative detection approach using NOBIAS chelate resins and HPLC may widen the application of NOBIAS chelate resins for quantitative detection of more water samples.

Development of Rapid and Specific Detection for the Human Aichivirus A Using the Loop-Mediated Isothermal Amplification from Water Samples

Human Aichivirus A (AiV-A) is classified as a Kobuvirus, group IV positive sense single strand RNA viruses. The first outbreak of AiV-A was reported from Aichi Prefecture, Japan in 1989. AiV-A exists not only among clinical patients, such as diarrhea, but also in a variety of water environments, as its occurrence is reported across a wide geographical range, from developing to advanced countries. For diagnose of AiV-A from water samples, mostly polymerase chain reaction (PCR) system have been developed. However, loop-mediated isothermal amplification (LAMP) assay has not been applied. In this study, developed a LAMP method to achieve a rapid, specific and highly sensitive detection of AiV-A. The method developed in this study is aimed specifically at AiV-A. Through a specific and non-specific selection and sensitivity test process for the five prepared LAMP primer sets, one primer set and optimum reaction temperature were selected. A newly developed method was more rapid (approximately 2–8 h), specific and equivalent detection of AiV-A than with the conventional PCRs. In addition, confirm system of positive LAMP reaction was developed by using the restriction enzyme Aci I and Hae III. For evaluation and verification of developing LAMP assay, a was applied to twenty cDNA from groundwater samples. This study proved rapid and specific diagnosis of AiV-A from water samples, and it is also demanded to be applicable to other environmental, clinical and food samples.

Ultrasensitive impedimetric mercury(II) sensor based on thymine-Hg(II)-thymine interaction and subsequent disintegration of multiple sandwich-structured DNA chains

An impedimetric method is described for ultrasensitive analysis of mercury(II). It is based on thymine-Hg(II)-thymine interaction which causes the disintegration of multiple-sandwich structured DNA chains. DNA strands were selected that are partially complementary to the T-rich Hg(II)-specific oligonucleotides (MSO). They were immobilized on a gold electrode via Au-S interaction. Next, the MSO and the bridging strands (BS) that can connect adjacent MSOs were alternately attached through layer-by-layer hybridization. Thus, a multiple-sandwich structured interface in created that carries numerous MSOs. This leads to a change-transfer resistance (R_ct) values of the electrode-electrolyte interface at faradic electrochemical impedance spectroscopy measurements in the presence of the hexacyanoferrate(II)/(III) redox probe at 0.2 V (vs. Ag/AgCl). If Hg(II) is added to the solution, the MSOs selectively interact with Hg(II) to produce T-Hg(II)-T structures. Hence, the multiple-sandwich hybridization chains become disintegrated, and this causes a decrease in resistivity. The effect can be used to quantify Hg(II) over an analytical range that extends over four orders of magnitude (1 fM to 10 pM), and it has a 0.16 fM limit of detection under optimal conditions. Graphical abstract An electrochemical sensor for femtomolar level detection of Hg²⁺ is realized on the basis of thymine-Hg²⁺-thymine interaction which causes disintegration of multiple sandwich DNA hybridization strands.

Assessment of the cytotoxic and mutagenic potential of the Jialu River and adjacent groundwater using human-hamster hybrid cells

The Jialu River in China has been seriously polluted by the direct discharge of industrial and domestic wastewater. The predominant contaminants of the Jialu River and its adjacent groundwater were recently investigated. However, the potential genotoxic impact of polluted water on human health remains to be clarified. Here, we used human-hamster hybrid (A_L) cells, which are sensitive for detecting environmental mutagens. We found that the cytotoxicity and mutagenicity of the groundwater in the Jialu River basin were influenced by the infiltration of the Jialu River. Hydrological periods significantly affected the cytotoxicity, but not the mutagenic potential, of surface and groundwater. Further, the mutagenic potential of groundwater samples located <1km from the Jialu River (S_M-2 water samples) was detected earlier than that of groundwater samples located approximately 20km from the Jialu River (S_N water samples). Because of high cytotoxicity, the mutagenic potential of water samples from the Jialu River (S_M-1 water samples) was not significantly enhanced compared with that of untreated controls. To further assess the mutagenic dispersion potential, an artificial neural network model was adopted. The results showed that the highest mutagenic potential of groundwater was observed approximately 10km from the Jialu River. Although further investigation of mutagenic spatial dispersion is required, our data are significant for advancing our understanding of the origin, dispersion, and biological effects of water samples from polluted areas.

A glassy carbon electrode modified with cerium phosphate nanotubes for the simultaneous determination of hydroquinone, catechol and resorcinol

A nafion film containing cerium phosphate nanotubes was pasted onto a glassy carbon electrode (GCE) to obtain a sensor for hydroquinone (HQ). The morphologies and components of the coating were characterized by transmission electron microscopy, scanning electron microscopy and energy-dispersive spectroscopy. Cyclic voltammetry and differential pulse voltammetry (DPV) showed the specific surface of the electrode to be significantly increased and the electron transfer rate to be accelerated. The modified GCE was applied to the determination of hydroquinone (HQ) via DPV. The oxidation current increases linearly in the 0.23 μM to 16 mM HQ concentration range which is as wide as five orders of magnitude. The limit of detection is 0.12 μM (based on a signal-to-noise ratio of 3), and the sensitivity is 1.41 μA·μM^-1 cm^-2. The method was further applied to the simultaneous determination of HQ, catechol and resorcinol. The potentials for the three species are well separated (20, 134, and 572 mV vs SCE). Average recoveries from (spiked) real water samples are between 95.2 and 107.0%, with relative standard deviations of 0.9~2.7% (for n = 3) at three spiking levels. The method was validated by independent assays using HPLC. Graphical abstract ᅟ.

The alternative use of layered double hydroxides as extraction medium coupled with microcomplexation for determination of phosphate in water samples

A simple, rapid, in situ, and green extraction combined with a microcomplexation has been developed for the spectrophotometric determination of phosphate in water samples. Through their formation, layered double hydroxides (LDHs) were employed as the extraction medium, instantly commenced by a rapid addition of a mixed solution of Mg²⁺ and Al³⁺ ions into alkaline phosphate solution. After the extraction, LDH precipitate containing phosphate was dissolved by sulfuric acid and the released phosphate was subsequently detected via its complexation with molybdate in the presence of antimonyl and ascorbic acid. Under optimum conditions, the linearity in the range of 5-200μgL^-1, with the correlation coefficient (r²) of 0.9969, and the enrichment factor (EF) of 14 were obtained. The limit of detection (LOD) of 5μgL^-1 and good precision, with the relative standard deviations (RSDs) less than 8.16%, were achieved. The proposed method was successfully applied to determine phosphate in water samples and the relative recoveries of 72.97-115.32% were obtained.

Molecular evidence of Sarcocystis nesbitti in water samples of Tioman Island, Malaysia

Background

Sarcocystis are intracellular protozoan parasites that are characterised by their ability to invade muscle tissue and form intramuscular sarcocysts. A muscular sarcocystosis outbreak was reported by travellers returning from Tioman Island in 2011 and 2012 where Sarcocystis nesbitti was identified as the main cause. The source of the S. nesbitti that was involved has remained elusive, although water is hypothesised to be the main cause of transmission. A surveillance study was therefore undertaken in the northern regions of Tioman Island to identify the source of S. nesbitti by screening rivers, water tanks, wells and seawater.

Methods

Water samples were collected from rivers, water tanks, wells and seawater on Tioman Island over the course of April to October 2015. Water samples were indirectly screened for Sarcocystis species by obtaining sediment from respective water sources. PCR amplification of the 18S rRNA gene region was conducted to identify positive samples. Microscopy was used in an attempt to reappraise PCR results, but no sporocysts were detected in any of the samples.

Results

A total of 157 water samples were obtained and 19 were positive for various Sarcocystis species. Through BLASTn and phylogenetic analysis, these species were found to be S. singaporensis, S. nesbitti, Sarcocystis sp. YLL-2013 and one unidentified Sarcocystis species.

Conclusions

This is the first positive finding of S. nesbitti in water samples on Tioman Island, which was found in a water tank and in river water samples. This finding supports the hypothesis that water was a potential medium for the transmission of S. nesbitti during the outbreak. This will potentially identify areas in which preventive measures can be taken to prevent future outbreaks.

Determination of iron (III) in food, biological and environmental samples

The nanodrop spectrophotometric (NDS) determination of iron (III) in water samples has been established. The proposed method is simple, selective and highly sensitive. The extraction of Fe (III)-thiocyanate complex was done by novel organic reagents such as N-phenylacetamide, N-alkylacetamide, (alkyl=butyl, hexyl and octyl group) in chloroform. The Fe (III) extract was examined in the strong acidic (HCl+H₂SO₄) solution. The maximum value of molar absorptivity was found to be 1.8×10⁵Lmol^-1cm^-1 at λ_max, 477nm (⩾9 fold enrichments) for N-octylacetamide (N-OAA). The method obeys the Beers Law within the range of 0.05μgmL^-1-6.0μgmL^-1. The detection limit and RSD value of the method were found to be 5ppb and 0.5906% respectively. The correlation coefficient, slope and intercept were calculated and found to be 0.9989, 0.1112, and 0.0048, respectively. The proposed method was successfully applied to the determination of trace amount of iron (III) in food, biological and environmental samples.

Fabric phase sorptive extraction: Two practical sample pretreatment techniques for brominated flame retardants in water

Sample pretreatment is the critical section for residue monitoring of hazardous pollutants. In this paper, using the cellulose fabric as host matrix, three extraction sorbents such as poly (tetrahydrofuran) (PTHF), poly (ethylene glycol) (PEG) and poly (dimethyldiphenylsiloxane) (PDMDPS), were prepared on the surface of the cellulose fabric. Two practical extraction techniques including stir bar fabric phase sorptive extraction (stir bar-FPSE) and magnetic stir fabric phase sorptive extraction (magnetic stir-FPSE) have been designed, which allow stirring of fabric phase sorbent during the whole extraction process. In the meantime, three brominated flame retardants (BFRs) [tetrabromobisphenol A (TBBPA), tetrabromobisphenol A bisallylether (TBBPA-BAE), tetrabromobisphenol A bis(2,3-dibromopropyl)ether (TBBPA-BDBPE)] in the water sample were selected as model analytes for the practical evaluation of the proposed two techniques using high-performance liquid chromatography (HPLC). Moreover, various experimental conditions affecting extraction process such as the type of fabric phase, extraction time, the amount of salt and elution conditions were also investigated. Due to the large sorbent loading capacity and unique stirring performance, both techniques possessed high extraction capability and fast extraction equilibrium. Under the optimized conditions, high recoveries (90-99%) and low limits of detection (LODs) (0.01-0.05 μg L(-1)) were achieved. In addition, the reproducibility was obtained by evaluating the intraday and interday precisions with relative standard deviations (RSDs) less than 5.1% and 6.8%, respectively. The results indicated that two pretreatment techniques were promising and practical for monitoring of hazardous pollutants in the water sample. Due to low solvent consumption and high repeated use performance, proposed techniques also could meet green analytical criteria.

Ionic liquid-modified silica-coated magnetic nanoparticles: promising adsorbents for ultra-fast extraction of paraquat from aqueous solution

In the present study, ionic liquid-modified silica-coated magnetic nanoparticles (Fe3O4@SiO2@IL) were synthesized and applied as adsorbents for extraction and determination of paraquat (PQ) followed by high-performance liquid chromatography. For assurance of the extraction efficiency, the obtained results were compared with those obtained by bared magnetic nanoparticles (MNPs). Experimental design and response surface methodology were used for optimization of different parameters which affect extraction efficiency of paraquat using both adsorbents. Under the optimized conditions, extraction recoveries in the range of 20-25 and 35-40 % with satisfactory repeatability values (RSDs%, n = 4) less than 5.0 % were obtained for bared MNPs and Fe3O4@SiO2@IL, respectively. The limits of detection were 0.1 and 0.25 μg/L using Fe3O4@SiO2@IL and bared MNPs, respectively. The linearity was obtained in the range of 0.25 to 25 μg/L and 0.5 to 25 μg/L for Fe3O4@SiO2@IL and bared MNPs, respectively, with the coefficients of determination better than 0.9950. Finally, Fe3O4@SiO2@IL was chosen as superior adsorbent due to more dispersion ability, higher extraction recovery, lower detection limit, as well as better linearity and repeatability. Calculated errors (%) were in the range of 3 to 10 % depicting acceptable accuracy for the analysis of PQ by the proposed method. Finally, the method was successfully applied for extraction and determination of PQ in some water and countryside soil samples.

Ultra-high performance liquid chromatography-electrospray tandem mass spectrometry for the analysis of antibiotic residues in environmental waters

An optimized solid-phase extraction (SPE) and ultra-high performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS) method was developed for the effective analysis of 35 antibiotics including sulfonamides (SAs), quinolones (QLs), tetracyclines (TCs), macrolides (MALs), lincomycin (LIN), and chloramphenicol (CAP). The addition of 0.1% formic acid to the mobile phase was favorable for the formation of [M + H](+) and the enhancement in the detection signals, but using ammonium formate decreased [M + H](+) with a corresponding reduction in the response of CAP. The optimal pH range for the SPE was 4.5 ∼ 5.0 with 6 mL aqueous ammonia/methanol (5/95, v/v) as the optimized eluent. An internal standard (IS) was selected for each type of analytes based on similarities in classification and retention time. The detection was completed in less than 10 min and was excellent with method detection limits (MDL) of 0.29 ∼ 4.03 ng/L. The recoveries of the antibiotics in samples from ultrapure water and groundwater were 67.13 ∼ 93.00% and 68.91 ∼ 92.67%, respectively. The antibiotics in samples collected from wastewater, surface water, and groundwater were also effectively detected. This newly developed method has the advantages of short detection times, small sample consumption, excellent reproducibility, and high sensitivity. This provides a reliable and promising technique for the simultaneous detection and monitoring of various residual antibiotics in aqueous environmental samples.

Natural radionuclides tracing in marine surface waters along the northern coast of Oman Sea by combining the radioactivity analysis, oceanic currents and the SWAN model results

This study aims to establish a managed sampling plan for rapid estimate of natural radio-nuclides diffusion in the northern coast of the Oman Sea. First, the natural radioactivity analysis in 36 high volume surface water samples was carried out using a portable high-resolution gamma-ray spectrometry. Second, the oceanic currents in the northern coast were investigated. Then, the third generation spectral SWAN model was utilized to simulate wave parameters. Direction of natural radioactivity propagation was coupled with the preferable wave vectors and oceanic currents direction that face to any marine pollution, these last two factors will contribute to increase or decrease of pollution in each grid. The results were indicated that the natural radioactivity concentration between the grids 8600 and 8604 is gathered in the grid 8600 and between the grids 8605 and 8608 is propagated toward middle part of Oman Sea.

Extraction and determination of sulfonylurea herbicides in water and soil samples by using ultrasound-assisted surfactant-enhanced emulsification microextraction and analysis by high-performance liquid chromatography

An ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) with low-density extraction solvents was developed for the extraction of sulfonylurea herbicides from water and soil samples prior to high-performance liquid chromatography coupled with ultraviolet detection (HPLC-UV). In this technique, a surfactant was used as emulsifier which could enhance the dispersion of water-immiscible extraction solvent into aqueous phase and was favorable for the mass-transfer of the analytes from aqueous phase to organic phase. The target analytes were extracted into an extraction phase (Aliquat-336 in 1-octanol) and dispersed in an aqueous solution. After extraction and phase separation, the organic solvent on top of the solution was withdrawn into a syringe and 20 µL of it was injected into a HPLC instrument for analysis. Influential factors in extraction were investigated and optimized. Under optimum experimental conditions, calibration curve was linear in the concentration range from 1 to 100 µg/L, with coefficients of estimation (R(2) values) varying from 0.9928 to 0.9952, and satisfactory repeatabilities (4.7<RSDs%<6.1) were attained. High preconcentration factors were achieved ranging from 103 to 153. Applicability of the method to the extraction of sulfonylurea herbicides from different types of complicated matrices, such as water and soil samples, was studied. The obtained results indicated that the proposed method is efficient, fast and inexpensive for extraction and determination of sulfonylurea herbicides in environmental aqueous and soil samples.

Optimization of a greener method for removal phenol species by cloud point extraction and spectrophotometry

A greener method based on cloud point extraction was developed for removing phenol species including 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 4-nitrophenol (4-NP) in water samples by using the UV-Vis spectrophotometric method. The non-ionic surfactant DC193C was chosen as an extraction solvent due to its low water content in a surfactant rich phase and it is well-known as an environmentally-friendly solvent. The parameters affecting the extraction efficiency such as pH, temperature and incubation time, concentration of surfactant and salt, amount of surfactant and water content were evaluated and optimized. The proposed method was successfully applied for removing phenol species in real water samples.

Speciation analysis of mercury in water samples by dispersive liquid-liquid microextraction coupled to capillary electrophoresis

In this study, a method of pretreatment and speciation analysis of mercury by dispersive liquid-liquid microextraction along with CE was developed. The method was based on the fact that mercury species including methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and Hg(II) were complexed with 1-(2-pyridylazo)-2-naphthol to form hydrophobic chelates and l-cysteine could displace 1-(2-pyridylazo)-2-naphthol to form hydrophilic chelates with the four mercury species. Factors affecting complex formation and extraction efficiency, such as pH value, type, and volume of extractive solvent and disperser solvent, concentration of the chelating agent, ultrasonic time, and buffer solution were investigated. Under the optimal conditions, the enrichment factors were 102, 118, 547, and 46, and the LODs were 1.79, 1.62, 0.23, and 1.50 μg/L for MeHg, EtHg, PhHg, and Hg(II), respectively. Method precisions (RSD, n = 5) were in the range of 0.29-0.54% for migration time, and 3.08-7.80% for peak area. Satisfactory recoveries ranging from 82.38 to 98.76% were obtained with seawater, lake, and tap water samples spiked at three concentration levels, respectively, with RSD (n = 5) of 1.98-7.18%. This method was demonstrated to be simple, convenient, rapid, cost-effective, and environmentally benign, and could be used as an ideal alternative to existing methods for analyzing trace residues of mercury species in water samples.