Metal Ions In Environmental Samples Research Articles

Fluorescent multichannel sensor array based on three carbon dots derived from Tibetan medicine waste for the quantification and discrimination of multiple heavy metal ions in water.

Afluorescent multichannel sensor array has been establishedbased on three carbon dots derived from Tibetan medicine waste for rapid quantification and discrimination of six heavy metal ions. Due to the chelation between metal ions and carbon dots (CDs), this fluorescence "turn off" mode sensing array can quantify six metal ions as low as "μM" level. Moreover, the six heavy metal ions display varying quenching effects on these three CDs owing to diverse chelating abilities between each other, producing differential fluorescent signals for three sensing channels, which can be plotted as specific fingerprints and converted into intuitive identification profiles via principal component analysis (PCA) and hierarchical cluster analysis (HCA) technologies to accurately distinguish Cu2+, Fe3+, Mn2+, Ag+, Ce4+, and Ni2+ with the minimum differentiated concentration of 5μM. Valuably, this sensing array unveils good sensitivity, exceptional selectivity, ideal stability, and excellent anti-interference ability for both mixed standards and actual samples. Our contribution provides a novel approach for simultaneous determination of multiple heavy metal ions in environmental samples, and it will inspire the development of other advanced optical sensing array for simultaneous quantification and discrimination of multiple targets.

Synthesis of Quinoline-based New Organic Chemosensors and its Application in Fluorophoric Detection of Metal-ions in Environmental Samples and Confirmation of Results using Molecular Modelling: A Complete Study

Quinoline-based two new ligands have been synthesized (QL1 and QL2) by reacting 8-quinoline carboxylic acid with derivatives of L-valine under a condensation reaction. The synthesized ligands were characterized by spectroscopic techniques such as 1H NMR, UV, IR, HRMS and CHNS. The 3D structures of both ligands were optimized for the lowest energy and the HOMO-LUMO orbitals were developed. The photoluminescence analysis of both ligands showed the fluorescence emission wavelengths on 492 and 508 nm, respectively for QL1 and QL2. The substituents on the quinoline ring influence the change in fluorescence emission wavelengths. Synthesized ligands acted as selective fluorescence turn-off chemosensors for Cu2+ ions and demonstrated the sensitive detection of Cu2+ ions in different water samples at the nanomolar scale. The interaction between metal ion and ligands were also studied by developing DFT structures.

Electrochemical and Colorimetric Nanosensors for Detection of Heavy Metal Ions: A Review.

Human exposure to acute and chronic levels of heavy metal ions are linked with various health issues, including reduced children's intelligence quotients, developmental challenges, cancers, hypertension, immune system compromises, cytotoxicity, oxidative cellular damage, and neurological disorders, among other health challenges. The potential environmental HMI contaminations, the biomagnification of heavy metal ions along food chains, and the associated risk factors of heavy metal ions on public health safety are a global concern of top priority. Hence, developing low-cost analytical protocols capable of rapid, selective, sensitive, and accurate detection of heavy metal ions in environmental samples and consumable products is of global public health interest. Conventional flame atomic absorption spectroscopy, graphite furnace atomic absorption spectroscopy, atomic emission spectroscopy, inductively coupled plasma-optical emission spectroscopy, inductively coupled plasma-mass spectroscopy, X-ray diffractometry, and X-ray fluorescence have been well-developed for HMIs and trace element analysis with excellent but varying degrees of sensitivity, selectivity, and accuracy. In addition to high instrumental running and maintenance costs and specialized personnel training, these instruments are not portable, limiting their practicality for on-demand, in situ, field study, or point-of-need HMI detection. Increases in the use of electrochemical and colorimetric techniques for heavy metal ion detections arise because of portable instrumentation, high sensitivity and selectivity, cost-effectiveness, small size requirements, rapidity, and visual detection of colorimetric nanosensors that facilitate on-demand, in situ, and field heavy metal ion detections. This review highlights the new approach to low-cost, rapid, selective, sensitive, and accurate detection of heavy metal ions in ecosystems (soil, water, air) and consumable products. Specifically, the review highlights low-cost, portable, and recent advances in smartphone-operated screen-printed electrodes (SPEs), plastic chip SPES, and carbon fiber paper-based nanosensors for environmental heavy metal ion detection. In addition, the review highlights recent advances in colorimetric nanosensors for heavy metal ion detection requirements. The review provides the advantages of electrochemical and optical nanosensors over the conventional methods of HMI analyses. The review further provides in-depth coverage of the detection of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) ions in the ecosystem, with emphasis on environmental and biological samples. In addition, the review discusses the advantages and challenges of the current electrochemical and colorimetric nanosensors protocol for heavy metal ion detection. It provides insight into the future directions in the use of the electrochemical and colorimetric nanosensors protocol for heavy metal ion detection.

Thermodynamics of Ag(I) Complex Formations with 2-Mercaptoimidazole in Water−Dimethyl Sulfoxide Solvents

The stability of coordination compounds of metal ions with ligands is of fundamental importance for elaborating upon practical sensors for the detection and quantification of metal ions in environmental samples. In this work, the stability constants of silver(I) complexes with 2-mercaptoimidazole (2MI) in a mixed water–dimethyl sulfoxide (DMSO) solvent were determined at 298.15 K and 308.15 K. It was found that with increasing temperature, the stability of the complexes decreases. The dependence of lgβ1 on the water−DMSO solvent compositions has its minimum at a concentration of dimethyl sulfoxide of 0.1 mol. fr. To explain the effect of the solvent, the solvation characteristics of the reagents were analyzed. In this regard, the 2MI Gibbs energy of transfer from water to aqueous dimethyl sulfoxide solvents was determined, and the influence of the aqueous DMSO solvent on the thermodynamics of 2MI protonation was analyzed. The stabilization of the silver ion and 2MI during the transition from water to a water–DMSO solvent makes a negative contribution to the change in the Gibbs energy of complexation, while the solvation of a complex particle promotes the complex formation. As a result, the Gibbs energy transfer values are slightly increased. The results of these thermodynamic studies could be useful for the development of sensor materials based on mercaptoimidazoles.

Tree-based machine learning models assisted fluorescent sensor array for detection of metal ions based on silver nanocluster probe

The growing concern over heavy metal pollution and its impact on the environment and human health has led to a proliferation of research on the detection and differentiation of heavy metal ions. A novel fluorescent sensor array utilizing only one single Ag-nanoclusters (Ag NCs) was developed for the efficient detection of six metal ions. The Ag NCs probe was prepared by using poly(methyl vinyl ether-alt-maleic acid) (PMVEM) as the ligand and has different fluorescence properties in water and dimethyl sulfoxide (DMSO). The interaction between metal ions and Ag NCs resulted in a characteristic fluorescence variation pattern which was subsequently analyzed using various tree-based machine learning models. We have compared different combinations of classification models and pre-processing methods of which the K-Nearest Neighbors Classifier with the first five linear discriminants has the highest accuracy. Through the integration of concentration models within a tree-based pipeline optimization framework, six unique concentration regression models were selected for each metal ion. In addition, the developed sensor array could identify metal ions in binary mixtures. And it still kept high accuracy for the classification of six target metal ions in river water. In conclusion, the proposed framework was found to be effective in the detection of heavy metal ions in environmental samples, thus providing a promising approach for addressing heavy metal pollution.

Unravelling mechanism for detecting chromium on functionalized gold nanoparticles via a smartphone and spectrophotometric-based systems supported by CIEL*a*b* colour space and molecular dynamics

This paper demonstrates the application of smartphones as well as spectrophotometers as tools to demystify the mechanism leading to colour variation of 1,5-diphenylcarbazide functionalized gold nanoparticles (DPC-AuNPs) due to chromium addition. Colour Grab 3.6.1 app was used to capture and decode colours from samples containing DPC-AuNPs with different concentrations of hexavalent Chromium [Cr(VI)] standards. The presence of Cr(VI) aggregated DPC-AuNPs resulted in a colour change from pink to blue and a decrease in the peak intensity as accompanied by a red shift of the SPR peak to 670 nm.The R colour coordinates decreased as Cr(VI) concentration was increased to 16 µM then a rapid decrease was noted between 18–25 µM and G and B colour coordinates followed the same trend. Colour difference (∆E) increased significantly as the Cr(VI) concentration increased. A rapid decrease was noticed in the hue angle between 16–25 µM while chroma decreased significantly as the Cr(VI) concentration increased. Molecular dynamics calculation of a gold cluster was used to simulate the aggregation process. The calculated radial distribution [g(r)] from cluster models of the Cr-DPC complex was two-fold more than Cr-AuNPs. This was associated with the aggregation of gold nanoparticles leading to the appearance of the blue colour of AuNPs solution which was also supported by the intensity obtained from colour Grab. This study will potentially be applied in the future for the fabrication of a Lovibond photometer for the detection of metal ions in environmental samples.

Multi-ion imprinted polymers (MIIPs) for simultaneous extraction and preconcentration of Sb(III), Te(IV), Pb(II) and Cd(II) ions from drinking water sources

Simultaneous extraction and preconcentration of several potentially toxic metal ions have received great attention because of their toxicological effects on aquatic life and human beings. Multi-ion imprinted polymers (MIIP) have proved to be promising adsorbents with excellent specific recognition performance than single-ion imprinted polymer. Therefore, in this study, the MIIP strategy was employed for simultaneous extraction and enrichment of Sb(III), Cd(II), Pb(II) and Te(IV) ions from drinking water sources. MIIPs was used as a sorbent material in ultrasound-assisted dispersive solid phase extraction combined with inductively coupled plasma optical emission spectrometry (UA-DSPE/ICP-OES). The experimental parameters that affect the extraction efficiency and recovery of Sb(III), Cd(II), Pb(II) and Te(IV) were investigated using response surface methodology. Under optimum conditions, the enhancement factors, linear range, limit of detection (LOD) and limit of quantification (LOQ) were 37.7–51.1, 0.04–100 µg L-1, 0.011–0.28 µg L-1, 0.037–093 µg L-1, respectively. The intra-day (n = 10) and inter-day (n = 5) precision expressed as relative standard deviations (%RSDs,) were 3% and 5%, respectively. The proposed UA-DSPE/ICP-OES method was applied for preconcentration and determination of the trace metal ions in environmental samples. Furthermore, the accuracy of the method was evaluated using spiked recovery experiments and the percentage recoveries ranged from 95% to 99.3%.

Wavelength-Selective Activation of Photocaged DNAzymes for Metal Ion Sensing in Live Cells

RNA-cleaving DNAzymes are widely applied as sensors for detecting metal ions in environmental samples owing to their high sensitivity and selectivity, but their use for sensing biological metal ions in live cells is challenging because constitutive sensors fail to report the spatiotemporal heterogeneity of biological processes. Photocaged DNAzymes can be activated by light for sensing purposes that need spatial and temporal resolution. Studying complex biological processes requires logic photocontrol, but unfortunately all the literature-reported photocaged DNAzymes working in live cells cannot be selectively controlled by light irradiation at different wavelengths. In this work, we developed photocaged DNAzymes responsive to UV and visible light using a general synthetic method based on phosphorothioate chemistry. Taking the Zn2+-dependent DNAzyme sensor as a model, we achieved wavelength-selective activation of photocaged DNAzymes in live human cells by UV and visible light, laying the groundwork for the logic activation of DNAzyme-based sensors in biological systems.

Graphene Oxide Supported on Amberlite Resin for the Analytical Method Development for Enhanced Column Preconcentration/Sensitive Flame Atomic Absorption Spectrometric Determination of Toxic Metal Ions in Environmental Samples

Graphene oxide (GO)-layered nanosheets with a two-dimensional carbon lattice is linked to styrenic carbon of porous XAD polymeric resin via an azo spacer arm without utilizing any oxygen-containing functionality for the first time. The adopted synthesis approach makes all of the epoxy, hydroxyl, carbonyl, and carboxyl groups on the axial and basal planes of the GO sheet available for coordination with metal ions, and the introduction of hydrophilic character as result the highest preconcentration factor for Pb (500) was observed among the GO composites used as a solid-phase extractant in column operation. The developed analytical methodology using XAD–GO for the preconcentration of Pb, Cd, and Zn ions permits the use of an economically viable less sensitive atomic absorption spectrometry for their trace determination in water samples because of the enhanced quantification limit. The application of polymer-immobilized GO in a column sorts out the problem of escape of toxic GO into the environment, and unde...

Colorimetric detection of Cu2+ and UO22+ by mixed solvent effect

We herein report the synthesis of a novel 2-(2-pyridylazo)-5-(diethylamino) phenol (PADAP)-containing tetraphenylethene (TPE) derivative, T-PADAP, to examine the solvent effect in the selective colorimetric detection of Cu2+ and UO22+. We found that the coordination of metal ions was influenced by adjusting the H2O:DMSO ratio, which ultimately led to differently colored solutions in the presence of the two metal ions. More specifically, T-PADAP exhibited a purple color in the presence of Cu2+ in a DMSO/H2O mixture containing 60% water, and a blue color in the presence of UO22+ in a DMSO/H2O mixture containing 40% water. T-PADAP was therefore considered a suitable colorimetric sensor for both Cu2+ and UO22+. Importantly, this compound exhibited a high selectivity, a wide effective pH range, and good anti-interference qualities. As such, this system constitutes a simple method for the detection of both Cu2+ and UO22+ using a single colorimetric sensor and through facile variation in the solvent ratio. In addition, it illustrates the use of solvent effects to regulate the coordination abilities of sensors. We expect that this study will promote the development of novel recognition methods for metal ions in environmental 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.

Solid phase extraction of metal ions in environmental samples on 1-(2-pyridylazo)-2-naphthol impregnated activated carbon cloth

1-(2-Pyridylazo)-2-naphthol impregnated activated carbon cloth (PAN-imp-ACC) was prepared as a solid phase sorbent and, for the first time, was used for the simultaneous separation and preconcentration of trace amounts of lead, cadmium and nickel in water, soil and sewage sludge samples prior to determination by flame atomic absorption spectrometry (FAAS). The parameters governing the efficiency of the method were optimized, including the pH, the eluent type and volume, the sample and eluent flow rates, diverse ions effects and the sample volume. A preconcentration factor of 100 was achieved for all the metal ions, with detection limits of 0.1–2.8µgL−1 and relative standard deviations below 6.3%. The adsorption capacity of the PAN-imp-ACC for Pb(II), Cd(II) and Ni(II) ions was found to be 45.0mgg−1, 45.0mgg−1 and 43.2mgg−1, respectively. The method was validated by the analysis of the certified reference materials TMDA-64.2 fortified Lake Ontario water and BCR-146R Sewage Sludge Amended Soil (Industrial Origin). The procedure was applied to determine the analytes content in real samples.

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

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

Screen-printed carbon electrodes modified with a bismuth film for stripping voltammetric analysis of platinum group metals in environmental samples

The increasing use of platinum group metals, PGMs (e.g. platinum, palladium and rhodium) in catalytic converters and the increasing mining activities for these metals in South Africa, has increased the presence of these metals in the aquatic environment. For this reason, the developments of sensitive detection techniques for metal ions in environmental samples have been investigated in this study. The work reported in this paper describes the development of an adsorptive differential pulse stripping voltammetric procedure for the determination of palladium (Pd), platinum (Pt) and rhodium (Rh) in environmental samples collected from rivers in close proximity to mining activities in South Africa. A screen-printed carbon electrode coated with a bismuth film, SPCE/BiF was constructed. The optimisation of the experimental conditions performed, included an appropriate buffer solution for coating and the supporting electrolyte solution. The voltammetric procedure included pre-concentration of the metals using dimethylglyoxime (DMG) as chelating agent, followed by adsorptive differential pulse stripping voltammetry (AdDPSV) at appropriate deposition potentials for each of Pd, Pt and Rh. Other essential stripping voltammetric parameters optimised included the DMG concentration, composition of the supporting electrolyte, pH, deposition time, and deposition potential. Interference studies in the presence of Ni and Co have also been conducted and showed promising results. The results obtained for this investigation have shown that the detection limits of 0.008μg/L, 0.006μg/L and 0.005μg/L were obtained for Pd(II), Pt(II) and Rh(III) determination respectively, using the SPCE/BiF sensor. The results obtained for Pd(II) determination of freshwater samples have shown that the concentration of Pd(II) in these samples ranged between 2.56–5.17±0.41 ppb (n=3). The results obtained for the Pt(II) concentrations ranged between 0.41–0.71±0.17 ppb (n=3). In the case of the Rh(III) determination, it was found to be 0.14–0.38±0.07 ppb (n=3). It was therefore concluded that the performance of the SPCE/BiF sensor was found to be more sensitive than the GCE/BiF sensor constructed in our laboratory in a previous study. It was further established that the SPCE/BiFE sensor delivers more sensitive results in ammonia buffer (pH=9.2) solution, compared to acetate buffer (pH=4.8) solution.

Spectrophotometric Determination of Copper as Copper Piperazine

Spectrophotometric method for determination of Cu(II) in the trace quantities was developed by using piperazine as ligand in ammonium acetate medium. The Procedure developed was applied for the estimation Cu(II) in microgram quantities in the samples of alloys and the method was found to be simple, rapid and comparable to routine analytical methods for trace level analysis of metal ions in environmental samples in any laboratory where sophisticated and expensive instruments are not available. UV visible spectrophotometer is cost effective and available in almost all laboratories. The complexes of piperazine in aqueous solutions are not reported so far and this is the first attempt in this area of spectrophotometric analysis.

Spectrophotometric Determination of Copper as Copper Piperazine

Spectrophotometric method for determination of Cu(II) in the trace quantities was developed by using piperazine as ligand in ammonium acetate medium. The Procedure developed was applied for the estimation Cu(II) in microgram quantities in the samples of alloys and the method was found to be simple, rapid and comparable to routine analytical methods for trace level analysis of metal ions in environmental samples in any laboratory where sophisticated and expensive instruments are not available. UV visible spectrophotometer is cost effective and available in almost all laboratories. The complexes of piperazine in aqueous solutions are not reported so far and this is the first attempt in this area of spectrophotometric analysis.

Theoretical and experimental studies on isotachophoresis in multi-moving chelation boundary system formed with metal ions and EDTA

In this paper, a general mode and theory of moving chelation boundary based isotachophoresis (MCB-based ITP), together with the concept of decisive metal ion (DMI) having the maximum complexation constant (lg Kmax) with the chelator, were developed from a multi-MCB (mMCB) system. The theoretical deductions were: (i) the reaction boundary velocities in the mMCB system at steady state were equal to each other, resulting in a novel MCB-based ITP separation of metal ions; (ii) the boundary directions and velocities in the system were controlled by the fluxes of chelator and DMI, rather than other metal ions; and (iii) a controllable stacking of metal ions could be simultaneously achieved in the developed system. To demonstrate the deductions, a series of experiments were conducted by using model chelator of EDTA and metal ions of Cu(II) and Co(II) due to characteristic colors of blue [Cu-EDTA](2-) and pink [Co-EDTA](2-) complexes. The experiments demonstrated the correctness of theoretical deductions, indicating the validity of the developed model and theory of ITP. These findings provide guidance for the development of MRB-based ITP separation and stacking of metal ions in biological sample matrix and heavy metal ions in environmental samples.

Rapid and nondestructive measurement of labile Mn, Cu, Zn, Pb and As in DGT by using field portable-XRF

The technique of diffusive gradients in thin films (DGT) is often employed to quantify labile metals in situ; however, it is a challenge to perform the measurements in-field. This study evaluated the capability of field-portable X-ray fluorescence (FP-XRF) to swiftly generate elemental speciation information with DGT. Biologically available metal ions in environmental samples passively preconcentrate in the thin films of DGT devices, providing an ideal and uniform matrix for XRF nondestructive detection. Strong correlation coefficients (r > 0.992 for Mn, Cu, Zn, Pb and As) were obtained for all elements during calibration. The limits of quantitation (LOQ) for the investigated elements of FP-XRF on DGT devices are 2.74 for Mn, 4.89 for Cu, 2.89 for Zn, 2.55 for Pb, and 0.48 for As (unit: μg cm(-2)). When Pb and As co-existed in the solution trials, As did not interfere with Pb detection when using Chelex-DGT. However, there was a significant enhancement of the Pb reading attributed to As when ferrihydrite binding gels were tested, consistent with Fe-oxyhydroxide surfaces absorbing large quantities of As. This study demonstrates the value of the FP-XRF technique to rapidly and nondestructively detect the metals accumulated in DGT devices, providing a new and simple diagnostic tool for on-site environmental monitoring of labile metals/metalloids.

Stripping voltammetric determination of palladium, platinum and rhodium in freshwater and sediment samples from South African water resources

Stripping voltammetry as technique has proved to be very useful in the analysis of heavy and other metal ions due to its excellent detection limits and its sensitivity in the presence of different metal species or interfering ions. Recent assessments of aquatic samples have shown increased levels of platinum group metals (PGMs) in aquatic ecosystems, caused by automobile exhaust emissions and mining activities. The development of an analytical sensor for the detection and characterisation of PGMs were investigated, since there is an ongoing need to find new sensing materials with suitable recognition elements that can respond selectively and reversibly to specific metal ions in environmental samples. The work reported shows the successful application of another mercury-free sensor electrode for the determination of platinum group metals in environmental samples. The work reported in this study entails the use of a glassy carbon electrode modified with a bismuth film for the determination of platinum (Pt2+), palladium (Pd2+) or rhodium (Rh2+) by means of adsorptive cathodic stripping voltammetry. Optimised experimental conditions included composition of the supporting electrolyte, complexing agent concentration, deposition potential, deposition time and instrumental voltammetry parameters for Pt2+, Pd2+ and Rh2+ determination. Adsorptive differential pulse stripping voltammetric measurements for PGMs were performed in the presence of dimethylglyoxime (DMG) as complexing agent. The glassy carbon bismuth film electrode (GC/BiFE) employed in this study exhibit good and reproducible sensor characteristics. Application of GC/BiFE sensor exhibited well-defined peaks and highly linear behaviour for the stripping analysis of the PGMs in the concentration range between 0 and 3.5 μg/L. The detection limit of Pd, Pt and Rh was found to be 0.12 μg/L, 0.04 μg/L and 0.23 μg/L, respectively for the deposition times of 90 s (Pd) and 150 s (for both Pt and Rh). Good reproducibility was also observed and the practical applicability of the sensor was demonstrated with the analysis of environmental water and sediment samples.

Recyclable fluorescent gold nanocluster membrane for visual sensing of copper(ii) ion in aqueous solution

Recently, metal-selective fluorescent chemosensors have attracted intense attention for their simple and real-time tracking of metal ions in environmental samples. However, most of the existing fluorescent sensors are one-off sensors and thus suffer from large amount of reagent consumption, significant experimental cost and raising the risk of environmental pollution. In this paper, we developed a green (low reagent consumption, low-toxicity reagent use), recyclable, and visual sensor for Cu(2+) in aqueous solution by using a fluorescent gold nanoclusters membrane (FGM) as the sensing unit, basing on our findings on gold nanoclusters (Au NCs) that the bovine serum albumin (BSA)-coated Au NCs exhibit excellent membrane-forming ability under the isoelectric point of BSA, and thus enable us to obtain a new type of sensing membrane (i.e. FGM) by denaturing Au NCs; the fluorescence of FGM can be significantly quenched by Cu(2+) ion, and the quenched fluorescence can be totally recovered by histidine; the as-prepared FGM is very stable and recyclable, which makes it an ideal sensing material.