Ions In Water Samples Research Articles

Screen-printed electrodes made of a bismuth nanoparticle porous carbon nanocomposite applied to the determination of heavy metal ions

This work reports on the simplified fabrication and on the characterization of bismuth-based screen-printed electrodes (SPEs) for use in heavy metal detection. A nanocomposite consisting of bismuth nanoparticles and amorphous carbon was synthesized by a combined one-step sol-gel and pyrolysis process and milled down to a specific particle size distribution as required for the preparation of an ink formulation to be used in screen printing. The resulting electrochemical devices were applied to the detection of Pb(II) and Cd(II) ions in water samples. The porous structure of carbon and the high surface area of the bismuth nanoparticles allow for the detection of Pb(II) and Cd(II) at concentration levels below 4 ppb. The application of the SPEs was demonstrated by quantifying these ions in tap drinking water and wastewater collected from an influent of an urban wastewater treatment plant.

Solid phase extraction of Cu (II), Ni (II), Co (II), and Fe (III) ions in water samples using salicylaldehyde benzoylhydrazone on Amberlite XAD-4 and their determinations by flame atomic absorption spectrometry

A multi element preconcentration procedure for solid phase extraction on Amberlite XAD-4 as their salicylaldehyde benzoylhydrazone chelates and flame atomic absorption spectrometric determination of some trace metal ions in water samples are proposed in this work. The influences of some analytical parameters, including pH of aqueous solution, amounts of reagent, flow rates of sample and eluent solutions, and sample volume on the quantitative recoveries of copper, nickel, cobalt, and iron were investigated. The effects of concomitant ions on the retentions of the analytes were also examined. The developed method has been successfully applied to the determination of metal ions in some real samples, including, tap water, river water, spring water, and waste water.

Preconcentration and separation of ultra-trace amounts of lead using ultrasound-assisted cloud point-micro solid phase extraction based on amine functionalized silica aerogel nanoadsorbent

A new method based on ultrasound-assisted cloud point-micro solid phase extraction (USA-CP-MSPE) with amine functionalized silica aerogel (AFSA) was used for separation and preconcentration of Pb(II) ions in water samples. At optimized pH, the mixture of AFSA and Triton X-100 as a nanoadsorbent and nonionic surfactant, respectively, was added to the aliquot of lead standard solution. Then, the sample was transferred to an ultrasound bath and placed in a thermostat water bath, and cooled in an ice-bath. In this step, the nanoadsorbent easily settled down in the surfactant phase and the enriched surfactant phase was separated from the aerogel nanoadsorbent by centrifugation. The analyte was back-extracted from nanoadsorbent with nitric acid solution (1.0M) and its concentration was determined by electrothermal atomic absorption spectrometry (ETAAS). Under the optimized conditions, the linear range was 0.04–1.45μgL−1 for Pb(II) and the limit of detection was evaluated as 0.01μgL−1 (peak area). An enrichment factor of 102 was achieved. Afterwards, the optimized method was applied to the determination of lead in real water samples that includes sea, river, tap and rain water.

A nanostructure ion-imprinted polymer for the selective separation and determination of copper ions in aqueous solutions

A new nanostructure Cu(II) ion-imprinted polymer (IIP) has been prepared using 1-(2-pyridylazo)-2-naphthol as a ligand. The Cu(II)–PAN complex was synthesized and polymerized in the presence of 2-vinylpyridine (the functional monomer), ethylene glycol dimethacrylate (the cross-linker) and 2,2′-azobisisobutyronitrile (the initiator) via precipitation polymerization using trapping method. The prepared IIP was characterized by FTIR spectroscopy, scanning electron microscopy, and transmission electron microscopy. The optimal pH value for the quantitative preconcentration was 6.0 and maximum sorbent capacity was 11.53 mg g−1. Under the optimized conditions, the method had a linear analytical range from 1 to 50 μg L−1. The detection limit, relative standard deviation, and recovery of the method were evaluated as 0.29 μg L−1, 3.6, and 94–97%, respectively. The developed method was successfully applied to the selective extraction and determination of trace amount of copper ions in water samples and some medicinal plants by inductively coupled plasma-optical emission spectrometry.

Lanthanum (III) Ion Determination by a New Design Optical Sensor

A new selective and sensitive Lanthanum (La) ions optical sensor based on immobilization of N-(2-aminoethyl)-salicylaldimine (AESI) on a triacetylcellulose membrane was prepared. The prepared optode exhibited a linear range of 30-150 part per billion (ppb) of the La (III) ion concentration with a detection limit of 14.38 ppb. The response time of the newly designed optode was derived within 30-60 s, depending on the La (III) ion concentration, however is independent to the pH of the solution in the range of 3-5. The proposed optode indicated a low detection limit, fast response time, and also remarkable selectivity regarding to the number of transition metals ions (i.e. Ce <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> , Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Cd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> , Zn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , and Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ). The optode was successfully regenerated with a thiourea solution, and its response which might be reversible and reproducible showed the relative standard deviation of less than 1.48%. This optode was applied for determining the La (III) ions in water samples.

Ultrasound assisted-dispersive-micro-solid phase extraction based on bulky amino bimodal mesoporous silica nanoparticles for speciation of trace manganese (II)/(VII) ions in water samples

This report described the use of amine-functionalized mesoporous silica UVM-7 as nanoadsorbent in ultrasound assisted-dispersive-micro-solid phase extraction (US-D-μ-SPE) procedure for rapid speciation/preconcentration of trace amounts of manganese (II) and manganese (VII) ions, from water samples prior to their determination by atom trapping-flame atomic absorption spectrometry (AT-F AAS). All main factors for the quantitative recoveries of Mn(II)/Mn(VII) ions were investigated and optimized. Based on the developed method, preconcentration and speciation of Mn(II) and Mn(VII) ions with NH2-UVM-7 were obtained in water samples due to the formation of –NH–Mn2+ and –NH3+–MnO4− at optimum pH of 8 and 5, respectively. The batch adsorption capacity of NH2-UVM-7 for Mn(II) and Mn(VII) ions was found to be 1733μmolg−1 and 570μmolg−1, respectively. Under the optimized conditions, limits of detection (3Sb/m), and limits of quantification (10Sb/m) were 0.007μgL−1 and 0.03μgL−1 for Mn(II) as well as 0.008μgL−1 and 0.04μgL−1 for Mn(VII). The preconcentration factors for Mn(II) and Mn(VII) were calculated as 102.3 and 98.8, and their relative standard deviations were 2.3 and 2.8%, respectively (n=10, C=10μgL−1). The developed method was successfully applied to natural water samples. The validation of the method was also performed by the standard reference material.

Facile Preparation of 2,6‐Pyridinedicarb­oxylic Acid Protected Gold Nanoparticles with Sensitive Chromium‐Ion Sensing and Efficient Catalysis

AbstractThe detection of Cr3+ and Cr6+ ions is very important as they are dangerous pollutants and carcinogens. Herein, we describe the preparation of 2,6‐pyridinedicarboxylic acid functionalized gold nanoparticles (PDCA–AuNPs) and their application as colorimetric sensors for the detection of Cr3+ and Cr6+ ions in water samples. The PDCA–AuNPs could be induced to aggregate quickly in the presence of Cr3+ ions, and the aggregation can be observed through the colorimetric response and special localized surface plasmon resonance (LSPR) of the gold nanoparticles. A linear response to the concentration of Cr3+ ions was observed from 10 nM to 1 μM. The detection limit is as low as 2 nM, which is below the maximum recommended contamination level of the World Health Organization for the chromium content (0.962 μM) in drinking water. The highly specific interactions of Cr3+ ions with PDCA–AuNPs provided excellent selectivity towards the detection of Cr3+ ions over other metal ions (Pb2+, Mg2+, Zn2+, Ni2+, Cu2+, Co2+, Ca2+, Mn2+, Fe2+, Cd2+, Ba2+, Cr6+, Ag+, Fe3+, Al3+, and Hg2+). Additionally, Cr6+ ions can be determined through the detection of Cr3+ ions after reduction by ascorbic acid. This method can offer the additional advantage of the efficient detection of Cr3+ and Cr6+ ions over other ions in environmental lake water. Additionally, the PDCA–AuNPs can be used as an efficient catalyst for the reduction of 4‐nitrophenol (4‐NP) and K3[Fe(CN)6].

Development of a Chemiluminescence Detecting System Based on FPGA

In order to detect weak chemiluminescence signal rapidly and high accurately, a chemiluminescence detection system is designed based on the core chip FPGA. The system uses a static injection mechanism as chemiluminescence reaction conduit. High-performance photodiode converts chemiluminescence signals into electrical signals replacing the traditional photomultiplier tube. It can meet the test requirements while reducing the cost of the detection system. The signal processing and storage system FPGA-based consists of A/D converter module, serial communication module, the keyboard scan control modules and memory modules. Nitrite ions in water samples are detected and the results show that in a certain concentration range the calibration curve of NO2-concentration and luminescence intensity is linear, the linear regression equation is Y = 0.4148X + 2.6508, and the correlation coefficient is R2= 0.9832. The relative standard deviation values are 2.7%(n=11).

Development of a cloud-point extraction method for determination of trace amounts of copper(II) in water samples

A simple and rapid cloud-point extraction method by using a Schiff base extractant, named bis(2hydroxynaphthaldehyde)-1,2-propanediimine, is presented for preconcentration of trace amounts of copper ions in water samples, prior to the determination by flame atomic absorption spectrometry. The process is based upon the complexation of Cu(II) ions by the Schiff base. The formed complexes are soluble in a micellar phase composed by the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114), and then are extracted into the surfactant-rich phase at above its cloud-point temperature. The effect of parameters influencing the extraction efficiency, such as aqueous solution pH, concentration of the Schiff base, amount of the surfactant, equilibration temperature and incubation time were investigated and discussed. Under the optimum experimental conditions, the calibration plot was linear in the range 1–400 µg/L with a limit of detection 0.3 µg/L. A preconcentration factor of 20 was achieved by the presented method. The proposed method was successfully applied for the determination of copper in various water samples.

Synthesis, characterization and application of ion imprinted polymeric nanobeads for highly selective preconcentration and spectrophotometric determination of Ni2 + ion in water samples

Here, the researchers report on the synthesis of ion imprinted polymeric (IIP) nanoparticles using a thermal polymerization strategy, and their usage for the separation of Ni2+ ion from water samples. The prepared Ni-IIP was characterized by colorimetry, FT-IR spectroscopy, and scanning electron microscopy. It was found that the particle size of the prepared particle to be 50–70nm in diameter with the highly selective binding capability for Ni2+ ion, with reasonable adsorption and desorption process. After preconcentration, bound ions can be eluted with an aqueous solution of hydrochloric acid, after their complexation with dimethylglyoxime, these ions can be quantified by UV–Vis absorption spectrophotometry. The effect of various parameters on the extraction efficiency including pH of sample solution, adsorption and leaching times, initial sample volume, concentration and volume of eluent were investigated. In selectivity study, it was found that imprinting causes increased affinity of the prepared IIP toward Ni2+ ion over other ions such as Na+, K+, Ag+, Co2+, Cu2+, Cd2+, Hg2+, Pb2+, Zn2+, Mn2+, Mg2+, Cr3+, and Fe3+. The prepared IIP can be used and regenerated for at least eight times without any significant decrease in binding affinities. The prepared IIP is considered to be promising and selective sorbent for solid-phase extraction and preconcentration of Ni2+ ion from different water samples.

Sampling of ammonium ion in water samples by using the diffusive-gradients-in-thin-films technique (DGT) and a zeolite based binding phase

We have investigated the possibility of sampling ammonium ion using the diffusive-gradients-in-thin-films technique (DGT) by introducing a novel binding agent that is based on micro-sized zeolite. The performance of zeolite-DGT was characterized by measurement of the following parameters: (1) the diffusion coefficient of ammonium ion in hydrogel; (2) the adsorption rate of ammonium ion by the zeolite binding gel; (3) the elution efficiency, and (4) the effects of pH, ionic strength and interfering ions on DGT. The method was validated by studying the uptake of ammonium ion from in freshwaters by zeolite gels which was found to be fast enough to meet the requirements of DGT. The concentrations determined via DGT agreed well with the concentrations determined in bulk solutions. Sampling of ammonium ion using zeolite-DGT was consistent over the pH 3 to 8 range and the 0.001 to 10 mM ionic strength range. The method also performs predictably in natural waters containing various metal ions. The technique is considered to be a viable passive tool for sampling ammonium from aqueous solutions.

A selective determination of copper ions in water samples based on the fluorescence quenching of thiol‐capped CdTe quantum dots

CdTe quantum dots (QDs) capped with different stabilizers, i.e. thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA) and glutathione (GSH) were investigated as fluorescent probes for the determination of Cu(2+). The stabilizer was shown to play an important role in both the sensitivity and selectivity for the determination of Cu(2+). TGA-capped CdTe QDs showed the highest sensitivity, followed by the MPA and GSH-capped CdTe QDs, respectively. The TGA- and MPA-capped CdTe QDs were not selective for Cu(2+) that was affected by Ag(+). The GSH-capped CdTe QDs were insensitive to Ag(+) and were used to determine Cu(2+) in water samples. Under optimal conditions, quenching of the fluorescence intensity (F0/F) increased linearly with the concentration of Cu(2+) over a range of 0.10-4.0 µg/mL and the detection limit was 0.06 µg/mL. The developed method was successfully applied to the determination of Cu(2+) in water samples. Good recoveries of 93-104%, with a relative standard deviation of < 6% demonstrated that the developed simple method was accurate and reliable. The quenching mechanisms were also described.

A sensitive electrochemical sensor for rapid and selective determination of nitrite ion in water samples using modified carbon paste electrode with a newly synthesized cobalt(II)-Schiff base complex and magnetite nanospheres

In this work, a simple and sensitive electrochemical sensor was developed for determination nitrite ion in water samples by using carbon paste electrode (CPE), which is modified with magnetite nanospheres as nanostructured materials and a newly synthesized cobalt(II)-Schiff base complex. The effects of various experimental parameters on the electrochemical oxidation response of the nitrite ions were investigated and optimized. At the optimum conditions the sensor has a linear response in the 0.2–30.0μmolL−1 concentration range and a low detection limit of 1.5×10−2μmolL−1 of nitrite. The results showed that the modified electrode has higher sensitivity toward nitrite ion in comparison with unmodified carbon paste electrode (CPE) and/or its nanomaterial-modified form. Obtained results showed that the modified electrode could be successfully applied for determination of nitrite in some water real samples.

Simple and sensitive colorimetric sensing of Cd2+ ion using chitosan dithiocarbamate functionalized gold nanoparticles as a probe

In this work, chitosan dithiocarbamate (CSDTC) derivative was successfully synthesized by mixing chitosan with carbon disulfide and ammonia at 45°C. Then, CSDTC (40μL, 1.0mg/mL) was added into Au NPs solution to obtain the chitosan dithiocarbamate functionalized gold nanoparticles (CSDTC-Au NPs). The Cd2+ ion was quickly induced the aggregation of CSDTC-Au NPs at PBS pH 8.0, which facilitates to develop a simple and selective colorimetric method for detection of Cd2+ ion. As a result, the characteristic surface plasmon resonance (SPR) peak of CSDTC-Au NPs at 523nm was red-shifted to 685nm, yielding a color change from red to blue. Under the optimized conditions, a linear relationship (R2=0.9991) was observed between the absorbance ratio at A685nm/A523nm and the concentration of Cd2+ in the range of 50–500μM. The limit of detection was found to be 63nM. Furthermore, CSDTC-Au NPs was applied to determine Cd2+ ion in water samples (drinking, tap, canal, river and industrial efluent).

Spectral and thermal characterization of salophen type Schiff base and its implementation as solid contact electrode for quantitative monitoring of copper(II) ion

Salophen templated Schiff base 2,3-bis(salicylaldimino)pyridine (H2IF) has been synthesized and fully characterized by a series of different spectroscopic methods and thermogravimetric analysis (TGA). It has been also further probed electrochemically and explored as a cation recognition ionophore in the form of a polymeric membrane as selective sensor for quantitative monitoring of Cu2+. Dielectric properties of the membrane have been studied by electrochemical impedance spectroscopy (EIS). The potentiometric results have demonstrated that the sensor exhibits very good selectivity and sensitivity towards Cu2+ over a wide variety of cations. The electrode has a linear response to Cu2+ with a detection limit of 4.46×10−8 and displays a Nernstian slope (29.14mV/decade) between pH 3.0 and 6.0 with a fast response time less than 10s. The solid contact electrodes have been exploited over five mounts period with good reproducibility. The analytical availability of the proposed electrode has been evaluated by applying in the determination of Cu2+ ions in water samples. The structural features and complexation of ionophore with Cu2+ have been monitored by UV–Vis spectroscopy and spectral findings have been further supported by DFT and TD-DFT calculations.

Colorimetric detection of sulfide ions in water samples based on the in situ formation of Ag2S nanoparticles

In this work, a facile approach to sensitively detect sulfide ions is developed. The proposed method is based on the findings that silver ions could oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to induce a blue color and an absorption peak centered at 652nm. The introduction of sulfide ions leads to the formation of Ag2S nanoparticles which act as catalyst to enhance the oxidation capacity of silver ions, resulting in a blue color burning and increase of the absorbance at 652nm. Based on the above facts, a facile method is developed to qualitatively and quantitatively detect sulfide ions by naked eyes and UV–vis spectroscopy, respectively. The color changes of the detection system in the presence of nanomolar level of sulfide ions could be distinguished by naked-eyes, demonstrating the high sensitivity of the method. Highly sensitive detection of sulfide ions can be achieved in the range of 1.0×10−9M to 8.0×10−8M, with a detection limit of 0.2nM. In addition, this method shows excellent selectivity toward sulfide ions detection and has been successfully applied to detect sulfide ions in tap water and lake water samples. Moreover, this method is simple without the preparation of nanomaterials and the need of complex readout instruments.

Linear sweep anodic stripping voltammetry: Determination of Chromium (VI) using synthesized gold nanoparticles modified screen-printed electrode

A highly sensitive electrochemical sensor has been constructed for determination of Cr(VI) with the lowest limit of detection (LOD) reported to date using gold nanoparticles (AuNPs) modified screen-printed electrode (SPE). The modification of SPE by casting pure AuNPs increases the sensitivity for detection of Cr(VI) ion using anodic stripping voltammetry. Cr(VI) ions are reduced to chromium metal on SPE-AuNPs by applying deposition potential of –1.1 V for 180 s. Afterwards, the oxidation peak current of chromium is obtained by linear sweep voltammetry in the range of −1.0 V to 0.2 V. Under the optimized conditions (HClO4, 0.06 mol L−1; deposition potential, –1.1 V; deposition time, 180s; scan rate, 0.1 V s−1), the limit of detection (LOD) was 1.6 pg mL−1. The fabricated electrode was successfully used for detection of Cr(VI) in tap and seawater. An electrochemical sensor has been constructed based on screen-printed electrode (SPE) modified with gold nanoparticles for determination of Cr(VI) ion in water samples. The coupling of anodic striping voltammetry with SPE modified nanostructures enhanced the sensitivity of electrochemical sensor for detection of Cr(VI) ion at low sample volumes.

Ionic liquid dispersive microextraction and spectrophotometric determination of trace uranyl ion in water samples

In the present study, spectrophotometric determination of uranyl with 2-(5-Bromo-2-pyridylazo)-5-(diethylamino) phenol after ionic liquid based microextraction has been developed. Effect of experimental parameters were optimized to achieve high sensitivity and stability of the complex. The analytical parameters such as linear range (1.33–670 µg L−1), limit of detection (0.97 µg L−1) and enrichment factor (150) were calculated for the method. The relative standard deviation of ten replicate measurement of uranyl was 6.53 and 2.59 % for 66 and 133 µg L−1 uranium, respectively. The proposed method was used to determine the uranyl ions in spiked water samples.

Copper nanocluster coupling europium as an off-to-on fluorescence probe for the determination of phosphate ion in water samples

This paper reports an “off-to-on” fluorescence (FL) probe for sensitively and selectively detecting phosphate ions (Pi's). Fabrication of the probe was based on the competition between Pi's and tannic acid-stabilized copper nanoclusters (TA-Cu NCs) for Eu3+ binding. The addition of Eu3+ ions to TA-Cu NCs triggered the aggregation of TA-Cu NCs, which quenched the FL of TA-Cu NCs. After Pi addition, the aggregated TA-Cu NCs solubilized into the aqueous solution to facilitate the Pi-triggered dispersion of TA-Cu NCs. This phenomenon was due to the stronger binding ability between Pi's and Eu3+ than that between TA and Eu3+, leading to FL recovery of Cu NCs. The degree of redispersion of TA-Cu NCs was directly related to Pi concentration. Thus, Pi concentration can be quantitatively determined by the change in FL of the TA-Cu NCs dispersion. Under the optimized conditions, the change in FL presented a linear relationship with Pi concentration from 0.07μmolL−1 to 80μmolL−1. The limit of detection for Pi was 9.6×10−3μmolL−1 at a signal-to-noise ratio of 3. For Pi determination in real samples, only 1mL water sample was needed. The proposed probe was highly sensitive, free from the interference of other common species in aqueous media, and particularly useful for the fast and simple diagnosis of water-eutrophication extent.

Removal and Preconcentration of Pb (II) and Cd (II) by Zero-Valent Iron Nanoparticles in Contaminated Water

Background: Lead (Pb) and cadmium (Cd) are two of the hazardous metals in the environment due to their acute and chronic effects on human health. Zero-valent iron nanoparticles (ZVINPs) are one of the adsorbents proposed as an efficient adsorbent for Pb and Cd. Objectives: This study evaluated the quantitative removal efficiency of Pb and Cd ions from contaminated water by ZVINPs. In addition, the capability of ZVINPs as a solid phase extractor for preconcentration and determination of Pb and Cd was investigated. Materials and Methods: Four samples, each from different water sources like Well water (Shushtar, Iran), Karoon River (Ahvaz, Iran), Caspian Sea (northern Iran) and Persian Gulf (southern Iran) were collected. Results: The elapsed time for quantitative removal of both Pb and Cd ions was two minutes. This method is applicable in a widespread range of pH and relatively high concentrations of electrolyte (NaCl) for the efficient removal (> 99%) of Pb and Cd ions in water samples. The adsorption of Pb and Cd ions on ZVINPs was well followed by the Langmuir model. The maximum adsorption amounts of Pb and Cd ions on ZVINPs were 96.5 and 58.3 mg/g, respectively. Limits of detection (LODs) of the method for lead and cadmium ions were 0.015 and 0.002 mg/L, respectively. The relative standard deviations for ten replicate determinations (Pb2+ 0.3 mg/L, Cd2+ 0.03 mg/L) were below 5%. The enrichment factors were more than 16 and 14 for Pb2+ and Cd2+, respectively. Conclusions: The proposed method is simple, fast, cost-effective and safe for the environment.