Ions In Environmental Samples Research Articles

A highly selective colorimetric sulfide assay based on the inhibition of the peroxidase-like activity of copper nanoclusters.

The authors report that sulfide ions are capable of inhibiting the peroxidase-like activity of copper nanoclusters (CuNCs). The catalytic activity of CuNCs toward the oxidation of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine by H2O2 is remarkably decreased in the presence of sulfide. Based on this finding, a colorimetric assay was developed for the rapid determination of sulfide. Best operated at a wavelength of 652nm, it has a 0.5μM detection limit. The method is highly selective and has been successfully applied to the quantification of sulfide in environmental water samples. Graphical abstract The catalytic activity of CuNCs toward the oxidation of 3,3',5,5'-tetramethylbenzidine by H2O2 is remarkably decreased in the presence of sulfide ions. This finding has been applied to design a method for colorimetric quantification of sulfide ions in environmental samples.

Green synthesis of surface-passivated carbon dots from the prickly pear cactus as a fluorescent probe for the dual detection of arsenic(iii) and hypochlorite ions from drinking water.

Efforts were made to develop a simple new approach for the green synthesis of surface-passivated carbon dots from edible prickly pear cactus fruit as the carbon source by a one-pot hydrothermal route. Glutathione (GSH) was passivated on the surface of the CDs to form a sensor probe, which exhibited excellent optical properties and water solubility. The prepared sensor was successfully characterized by UV-visible spectrophotometry, fluorescence spectrophotometry, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The simple sensing platform developed by the GSH-CDs was highly sensitive and selective with a “turn-off” fluorescence response for the dual detection of As3+ and ClO− ions in drinking water. This sensing system exhibited effective quenching in the presence of As3+ and ClO− ions to display the formation of metal complexes and surface interaction with an oxygen functional group. The oxygen-rich GSH-CDs afforded a better selectivity for As3+/ClO− ions over other competitive ions. The fluorescence quenching measurement quantified the concentration range as 2–12 nM and 10–90 μM with the lower detection limit of 2.3 nM and 0.016 μM for the detection of As3+ and ClO− ions, respectively. Further, we explored the potential applications of this simple, reliable, and cost-effective sensor for the detection of As3+/ClO− ions in environmental samples for practical analysis.

Potentiometric Determination of Cu2+ Ions in Environmental Samples Using a Newly Developed Cu2+-Selective Electrode Based on Schiff Base

Potentiometric Determination of Cu2+ Ions in Environmental Samples Using a Newly Developed Cu2+-Selective Electrode Based on Schiff Base

All-Solid-State Screen-Printed Sensors for Potentiometric Calcium(II) Determinations in Environmental Samples

This paper describes preparation, characterization and electrochemical performance of novel planar miniaturized all-solid-state (ASS) screen-printed potentiometric sensors for the detection of Ca2+ ions in environmental samples. Screen-printed graphite-based ion-selective electrodes (ISEs) and screen-printed reference electrodes based on silver-containing pastes have been applied in a space saving manner on common ceramic substrates with small dimensions. Applications to environmental samples are shown by direct potentiometry and potentiometric titrations in real water samples. Conducting polymers (CPs) have been used as solid-contact materials and as intermediate layer between the polyvinyl chloride (PVC)-containing ion-selective membrane and the graphite-containing substrate. Different diamides have been incorporated into the PVC membrane. In the range from 10-4 mol/L to 10-1 mol/L, the ISEs show linear slopes of 27 mV/decade, which is close to the Nernstian response. Moreover, the ISEs have response times of 6 months. The novel potentiometric ASS sensors enable simple and exact Ca2+ determinations in real samples.

A new strategy to design colorful ratiometric probes and its application to fluorescent detection of Hg(II)

A new strategy has been proposed to expand color-tunability of ratiometric fluorescent probes. It was shown that the combination of blue emissive color (as an internal standard) and yellow emissive color (as a probe) is an efficient way to create an extensive color range in ratiometric probes. However, due to the nature of the interaction between the analyte and the probe in terms of fluorescence quenching, occurance of the redshift in the emission is the major provision of such a probe. Our developed ratiometric fluorescence probe consists of blue emissive carbon dots (BCDs) and thioglycolic acid (TGA)-capped yellow emissive cadmium telluride (CdTe) quantum dots (YQDs). The ratiometric probe exhibits dual-emissions which are centered at 443 and 560 nm under a single excitation wavelength of 360 nm. With the exposure of Hg(II) ions (as an example) to the probe, the fluorescence of YQDs is selectively quenched and redshifted. The emission of probe displays continuous color changes from strong green into light green, yellow-green, yellow, orange, pink, purple, weak blue, and dark blue. The fluorescent ratiometric probe demonstrates a broad dynamic linear range from 10 nmol L−1 to 1.4 μmol L−1 with a detection limit as low as 4.6 nmol L−1. In addition, the wide-color-varying probe shows an excellent capacity to determine Hg(II) ions in environmental samples.

Ratiometric Fluorescent Chemosensor for Zn2+ Ions in Environmental Samples Using Supermicroporous Organic‐Inorganic Structures as Potential Platforms

AbstractWe report the fabrication of supermicroporous, fluorometric chemosensors with a Zr‐metal–organic framework as carrier. The fabricated ratiometric fluorescent chemosensors (RFCs) were suitable for the selective and sensitive fluorometric recognition of ultra‐trace concentrations of heavy metals, such as Zn2+ ions, in water sources. The RFCs were designed by performing direct pressure‐assisted immobilization of a hydrophobic organic probe inside supermicroporous cubic Zr‐MOFs. The immobilized organic probe exhibited high sensitivity and selectivity toward Zn2+ in a uniform super‐microchannel pore, long‐range intergrowing crystal structures. Ratiometric fluorometric sensing assay of the Zn2+ ions revealed the high selectivity of the ions in a mixture of multiple interfering ions. This phenomenon was due to the structure of the RFCs, the pH of the system, the composition of the competitive ion system, and the Zn‐to‐RFCs binding process, which occurred via electron transfer. The RFCs exhibited a wide detection and monitoring range for Zn2+ ions. The lower limit of detection was 0.16 ppb, and a fast response within seconds was observed during complexation with the Zn2+ ion target. The surface functionality and long‐term stability of RFCs enable the practical and multiple reuse/cycles of Zn2+ ion recognition.

Simple and selective paper-based colorimetric sensor for determination of chloride ion in environmental samples using label-free silver nanoprisms

Simple and selective paper-based colorimetric sensors using silver nanoprism (AgNPrs) were conveniently fabricated and developed for the determination of chloride ions (Cl−) contaminated in the environment. Samples containing different concentrations of Cl− were analyzed. The analysis is based on the oxidative etching of the AgNPrs into smaller silver nanospheres (AgNPss) by Cl−. In the presence of Cl−, the distinctive color change of the AgNPrs from dark-violet to red was rapidly visualized by the naked eye in 5min without the requirement of surface modification. For quantitative measurement using image processing, a good linear relationship (R2 = 0.996) between logarithmic of Cl− concentration and the average mean color intensity was obtained in the range of 10–1000mgL−1 with a detection limit of 1.3mgL−1. The developed sensors were investigated for precision, accuracy, and sensitivity and validated by the classical method. Statistical analysis proved that the developed sensors were precise, sensitive and accurate and can be used effectively for the analysis of Cl− in natural waters.

Tricyclic dihydropyrimidine-based multifunctional organic nanoparticles for detection of Ag (I) ions and spermidine: Real-Time application

In the present report a dihydropyrimidine-based Biginelli compound 1 was engineered into stable organic nanoparticles via reprecipitation method. The organic nanoparticles, N1 acted as an efficient fluorescent nanosensor for selective detection of Ag (I) ions via fluorescence quenching with a detection limit of 7.9nM. Furthermore, successful detection of spermidine (an important biogenic amine) was realized through an indirect metal ion mediated approach where the quenched fluorescence of complex, C was recovered with a red-shift on addition of spermidine. The lowest detection limit for spermidine was found to be 3.2nM. The nanosensor found applicability in a wide pH range from 3 to 12, which is appropriate for evaluation in environmental and physiological conditions. The selectivity for Ag (I) ions and spermidine was further confirmed with competitive binding studies which demonstrated no interference from other analytes. Moreover, real sample analysis established the practical applicability of the developed probes. The proposed strategy provides a facile, non-invasive, sensitive and economic platform for the estimation of Ag (I) ions in environmental samples (river water) and spermidine in biological samples (urine).

Trace analysis of nitrite ions in environmental samples by using in-situ synthesized Zein biopolymeric nanoparticles as the novel green solid phase extractor

For the first time, a novel green method using Zein biopolymeric nanoparticles as a green dispersive solid-phase extractor is reported for the separation and preconcentration of trace amount of nitrite (NO2-) ions in ppb levels. The Zein protein is a biodegradable hydrophobic plant protein that is obtained from corn and is composed of a number of hydrophobic amino acids. Zein bionanoparticles were synthesized in an anti-solvent process and used as a new biosorbent in the extraction technique. In the proposed technique, by using a standard method at first, a mixture of 1-naphthylamine and sulphanilic acid as selective regents was added to the samples, and in the presence of the nitrite ion, a red azo product was formed. After that, the ethanolic Zein solution (equal to 15mg) was injected rapidly into the sample, based on the anti-solvent process. Zein bionanoparticles (BNPs) were produced, the adsorbed colour product was separated by centrifugation, and finally samples were analysed with the spectrophotometric method. The influence of different variables such as pH, buffer and amount of buffer, amount of adsorbent and effect of time on extraction were investigated and Zein BNPs were characterized by TEM, SEM, and FT-IR techniques. The main advantages of Zein as a new solid-phase extractor are that this biopolymer is non-toxic, stable, widely available, biodegradable, very hydrophobic, and can be fabricated easily. Under optimal experimental conditions, the linear correlation coefficient (r2) was found to be 0.9972 at the concentration range of 5.0–1000ngmL−1. The limit of detection was 2.3ngmL−1 (0.05μM). This method was applied successfully for the analysis of sea and river waters as well as industrial wastewater samples. Finally, this method follows the US EPA (US Environmental Protection Agency) and WHO (World Health Organization) international standards for nitrite analysis. In addition, it has several advantages to warrant its applicability in the near future in separation science as a green biosorbent in both dispersive and normal solid-phase extraction.

Solidified floating organic drop microextraction for pre-concentration and trace monitoring of cadmium ions in environmental food and water samples

In this research, solidified floating organic drop microextraction as an efficient sample preparation method was used for trace monitoring of cadmium ions in environmental samples. In this method, a free microdroplet of 1-undecanol is floated on the surface of aqueous solution and agitated by a stirring bar placed on the bottom of the sample vial. Cadmium ions were complexed with neocuproine to obtain hydrophobic complex and extracted to extraction solvent. The extracted target ions were determined by flow injection–flame atomic absorption spectrometry. The effect of important factors on the extraction of target ions by the proposed sample preparation method was evaluated and optimized. The limit of detection, relative standard deviation (%) and enrichment factor of the method were 0.02, 3.7 and 98.5%, respectively. The validation of the method was examined by the analysis of cadmium ions in the certified reference material (sea food mix), and the obtained data can proof the reliability of the method for trace detection of cadmium ions. The method was successfully applied for determination of cadmium in the real food and water samples, and satisfactory relative recoveries (97–102%) were achieved.

Quantification of Zn2+ Ion in Environmental Samples by Fabrication of Pyrolytic Graphite Electrode Based on Schiff Bases of Hydrazinecarbothioamide Derivatives

Schiff base ligands 2,2′-(((ethane-1,2-diylbis(oxy))bis(2,1-phenylene))bis(methanylylidene))bis(hydrazinecarbothioamide) (L1), 2,2′-(((propane-1,3-diylbis(oxy))bis(2,1-phenylene))bis(methanylylidene))bis(hydrazinecarbothioamide) (L2) and 2,2′-((((oxybis(ethane-2,1-diyl))bis(oxy))bis(2,1-phenylene))bis(methanylylidene))bis(hydrazinecarbothioamide) (L3) have been synthesized and were explored as ion carrier in the construction of solid contact Zn2+ PVC based membrane sensor. The effect of plasticizers, benzylacetate (BA), dioctylphthalate (DOP), dibutylphthalate (DBP), 1-chloronaphthlene (1-CN) and o-nitro-phenyloctylether (o-NPOE) and anion excluders, sodium tetraphenylborate (NaTPB) and potassium tetrakis-p-(chlorophenyl)borate (KTpClPB) on the performance of the electrodes has also been investigated. Comparative studies performed on coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE) reveal the superiority of CPGE with optimized membrane composition of L2: PVC: DOP: NaTBP≡6:34:58:2 (w/w, mg) exhibits the best results with a wide working concentration range of 1.1 × 10−8–1.0 × 10−1 mol L−1, detection limit of 8.0 × 10−9 mol L−1, Nernstian slope of 29.6 ± 0.2 mV decade−1 of activity of Zn2+ ion in the pH range of 3.0–9.0. The sensor showed fast response time of 10 s and could be used over a period of 4 months without any significant divergence in slope, working concentration range and detection limit. The sensor was employed in the quantification of Zn2+ ion in various samples and also as an indicator electrode in the potentiometric titration of Zn2+ ion with EDTA.

Potentiometric sensor for the nanoscale monitoring of Ni2+ ion in environmental samples by the fabrication of coated pyrolytic graphite electrode based on a novel C–C-coupled compound

ABSTRACTNovel ligand 5,5ʹ-((3-nitrophenyl)methylene)bis(2,6-diaminopyrimidin-4(3H)-one) (L) was synthesised and characterised. Preliminary studies on L have showed that it has more affinity towards the Ni2+ ion. Thus, the L was used as the electroactive material in the fabrication of poly(vinyl chloride) (PVC)-based membrane sensors such as coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE). Several polymeric membranes were fabricated by incorporating L as ionophore, NaTPB as anion excluders and BA, 1-CN, DBP, DOP and o-NPOE as solvent mediators and their effect on potentiometric response studied. Comparative electroanalytical studies performed on the CGE and CPGE depict that the CPGE with optimised membrane composition of L:PVC:o-NPOE:NaTPB in the ratio of 7:33:58:2 (w/w, mg) exhibited the best response in terms of wide working concentration range from 2.0 × 10−8 to 1.0 × 10−1 mol L−1, (3.64 µg L−1 –18.2 g L−1) lower detection limit of 8.1 × 10–9 mol L−1 (1.47 µg L−1) with Nernstian compliance of 29.4 ± 0.2 mV decade−1 of activity of Ni2+ ion in the pH range of 3.5–9.0. The sensor can work satisfactorily in water–acetonitrile and water–methanol mixtures. It can tolerate 30% acetonitrile and 20% methanol content in the mixtures. The sensor showed fast response time of 8 s and could be used successfully for a period of 4 months. The sensor reflects its utility in the quantification of Ni2+ ion in real samples and has been successfully employed as an indicator electrode in the potentiometric titration of Ni2+ ion with EDTA.

Novel potentiometric sensor for selective monitoring of Ce3 + ion in environmental samples

Novel ligand 1,1′-(pyridine-2,6-diyl)bis(3-(1H-pyrrol-2-yl)prop-2-en-1-one) (L) was synthesised and explored as ion carrier for the selective monitoring of Ce3+ ion in various samples. Spectrophotometric and conductometric studies reveals high affinity of L towards Ce3+ ion and therefore, L was used in the fabrication of poly (vinyl chloride) based membrane sensor of coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE). Best performance was observed with the optimized membrane composition of L: PVC:o-NPOE:NaTPB::7:31:59:3 (w/w, mg). The CPGE exhibits wide working concentration range of (1.9×10−8–1.0×10−1molL−1) and low detection limit of 5.0×10−9molL−1 with Nernstian slope of 19.4±0.2mV−1 decade of activity. The sensor is independent of pH in the pH range of 3.0–8.5 and exhibited fast response time of 9s. The sensor can work satisfactorily in partially non-aqueous media of water-acetonitrile and water-ethanol (30%, v/v) and could tolerate about 20% (v/v) of water-methanol contents. The applicability of the sensor is illustrated by determining Ce3+ ion in real samples and as an indicator electrode in the potentiometric titration of Ce3+ ion with oxalate and fluoride ions.

An electrochemically reduced graphene oxide chemiresistive sensor for sensitive detection of Hg2+ ion in water samples

Divalent mercuric (Hg2+) ion is one of the most prevalent forms of mercury species in waters with high toxicity and bioaccumulation in the human body, for which sensitive and selective detection methods are highly necessary to carry out its recognition and quantification. Here an electrochemically reduced graphene oxide (RGO) based chemiresistive sensor was constructed and used for the detection of Hg2+ ion in various water samples. Monolayer GO sheets were assembled onto interdigitated electrodes, followed by reduction through linear sweep voltammetry and then modification with a single-stranded DNA aptamer. The electrochemically derived RGO based sensor showed selective response to as low as 0.5nMHg2+ ion in presence of other metal ions and matrices. A comparison between chemiresistive sensors prepared with electrochemically and chemically derived RGO showed that the former had better response performance for sensing Hg2+ ion. The proposed method provides a simple tool for rapid, selective and sensitive monitoring of Hg2+ ion in environmental samples.

In-situ formation of ion-association nanoparticles induced enhancements of resonance Rayleigh scattering intensities for quantitative analysis of trace Hg2 + ions in environmental samples

In this paper, Hg2+ ions are demonstrated to form anionic [HgI4]2− complexes after interacting with massive amount of I− ions. Subsequently, the addition of tetradecyl pyridyl bromide (TPB) can make [HgI4]2− anionic complexes react with univalent tetradecyl pyridyl cationic ions (TP+), forming dispersed ion-association complexes (TP)2(HgI4). Due to the extrusion action of water and Van der Waals force, the hydrophobic ion-association complexes aggregate together, forming dispersed nanoparticles with an average size of about 8.5nm. Meanwhile, resonance Rayleigh scattering (RRS) intensity is apparently enhanced due to the formation of (TP)2(HgI4) ion-association nanoparticles, contributing to a novel technique for Hg2+ detection. The wavelength of 365nm is chosen as a detection wavelength and several conditions affecting the RRS responses of Hg2+ are optimized. Under the optimum condition, the developed method is used for the determination of Hg2+ in aqueous solution and the detection limit is estimated to be 0.8ngmL−1. Finally, the practical application of the developed method can be confirmed through the detections of Hg2+ in waste and river water samples with satisfactory results.

Glutathione modified screen-printed carbon nanofiber electrode for the voltammetric determination of metal ions in natural samples

This work reports the development of a glutathione modified electrode via electrografting on a screen-printed carbon nanofiber substrate (GSH-SPCNFE). GSH-SPCNFE was compared to a classical screen-printed carbon electrode modified with glutathione (GSH-SPCE) for the simultaneous voltammetric determination of Cd(II) and Pb(II). Their electrochemical characterization and analytical performance suggest that SPCNFE could be a much better support for GSH immobilization. The applicability of GSH-SPCNFE for the determination of low concentration levels of Pb(II) and Cd(II) ions in environmental samples was successfully tested in a certified wastewater reference material by means of stripping voltammetry with a very high reproducibility and good trueness.

D2EHPA-impregnated alumina for adsorption of strontium ions in environmental samples

The alumina impregnated by the di-2-ethyl hexyl phosphoric acid was introduced to make more adsorption of strontium as well as to determine the optimal conditions. The influence of various parameters such as pH, equilibrium time, adsorbent mass, interfering ions, and various eluant agents for the desorption of the strontium ions, initial concentration, and temperature was investigated to find out the adsorption behavior of the adsorbent under different conditions. The adsorbent was characterized by the Fourier transform infrared spectroscopy. The experimental data were fitted on the two-parameter and three-parameter adsorption isotherm models. The Freundlich and Redlich–Peterson models have suitable fitting on the experimental data (R 2 = 0.9307). The kinetic models of adsorption were analyzed by the pseudo-first- and pseudo-second-order models. The results have been indicated that the pseudo-second-order kinetic model is more appropriate than the others. Advantages of our method were simple operation, less time for preparation of adsorbent, rapid phase separation, and capability to combine with various detection techniques. The method has been utilized to extract and the recovery of strontium ions in environmental aqueous samples.

Multi-Element Preconcentration/Separation of Some Metal Ions in Environmental Samples by Using Co-precipitation.

A preconcentration/separation system for cadmium(II), nickel(II), copper(II), lead(II), iron(II), cobalt(II), and manganese(II) ions has been established prior to their atomic absorption spectrometric determinations. The procedure is based on the co-precipitation of these ions by the aid of a praseodymium hydroxide (Pr(OH)3) precipitate. The precipitate was dissolved in 0.5 mL of concentrated HNO3, and made up to 10.0 mL with water. The analytes were determined by a flame atomic absorption spectrometer. The effects of analytical parameters including pH, amounts of praseodymium as carrier element, sample volume, etc. on the recoveries of heavy metals were investigated. The effects of matrix ions were also examined. The limits of detection for analyte ions were found in the range between 0.7-5.2 μg/L. The validation of this present procedure was verified by the analysis of certified reference materials, TMDA-54.4 (fortified water) and NIST 1570a (spinach leaves). The proposed co-precipitation procedure was applied for the determination of cadmium(II), nickel(II), copper(II), lead(II), iron(II), cobalt(II), and manganese(II) ions in various environmental water samples.

Application of a novel electrochemical sensor based on modified siliceous mesocellular foam for electrochemical detection of ultra-trace amounts of mercury ions

S-MCF particles were functionalized with dithizone groups, and applied as a new class of mesoporous electrode material for preconcentration and electrochemical detection of trace mercury ions in environmental samples.

Crown ether-modified electrodes for the simultaneous stripping voltammetric determination of Cd(II), Pb(II) and Cu(II)

This work describes the immobilization of 4-carboxybenzo-18-crown-6 (CB-18-crown-6) and 4-carboxybenzo-15-crown-5 (CB-15-crown-5) assisted by lysine on aryl diazonium salt monolayers anchored to the surface of graphite–epoxy composite electrodes (GEC), and their use for the simultaneous determination of Cd(II), Pb(II) and Cu(II) by differential pulse anodic stripping voltammetry (DPASV). These modified electrodes display a good repeatability and reproducibility with detection and quantification limits at levels of µgL−1 (ppb), confirming their suitability for the determination of Cd(II), Pb(II) and Cu(II) ions in environmental samples. The overlapped nature of the multimetal stripping measurements was resolved by employing the two-sensor array CB-15-crown-5-GEC and CB-18-crown-6-GEC, since the metal complex selectivity exhibited by the considered ligands could add some discrimination power. For the processing of the voltammograms, Discrete Wavelet Transform and Causal Index were selected as preprocessing tools for data compression coupled with an artificial neural network for the modeling of the obtained responses, allowing the resolution of mixtures of these metals with good prediction of their concentrations (correlation with expected values for an external test subset better than 0.942).