Chelation Reaction Research Articles

Confined construction of porous conductive framework Na3V2(PO4)3 nanocrystals and their ultrahigh rate and microtherm sodium storage performance

Sodium-ion batteries have been extensively studied due to their high safety and high natural abundance characteristics. Na3V2(PO4)3 (NVP) cathode materials, which have extraordinary rate performance and cycle stability, have become among the most promising cathode materials for commercialization. However, due to their low conductivity problem, it is still a serious challenge to develop a nanocrystalline and uniform conductive frame structure. This work reports a confinement reaction strategy derived from the chelation reaction, which can successfully realize electrode materials with adjustable internal NVP grains. The obtained ultrasmall grained carbon frame material showed to have ultrahigh rate performance, and it could reach 101 mAh g−1 at 100C and 100 mA h g−1 after 1800 cycles at 10C rate (capacity retention rate 99%). Moreover, it showed the characteristics of excellent low-temperature performance, and no capacity degradation at − 20 °C after 1000 cycles.

Imaging of Transmetallation and Chelation Phenomena Involving Radiological Contrast Agents in Mineral-Rich Fruits.

Exogenous heavy metals or non-metallic waste products, for example lanthanide or iodinated contrast media for radiological procedures, may interfere with the biochemical pools in patients and in common food sources, creating an excess buildup of exogenous compounds which may reach toxic levels. Although the mechanisms are unknown, our experiments were designed to test if this toxicity can be attributed to “transmetallation” or “chelation” reactions freeing up lanthanides or chelated transition metals in acidic fruits used as phantoms representing the biologically active and mineral-rich carbohydrate matrix. The rapid breakdown of stable contrast agents have been reported at a lower pH. The interaction of such agents with native metals was examined by direct imaging of contrast infused fresh apples and sweet potatoes using low energy X-rays (40–44 kVp) and by magnetic resonance imaging at 1.5 and 3T. The stability of the exogenous agents seemed to depend on endogenous counterions and biometals in these fruits. Proton spin echo MR intensity is sensitive to paramagnetic minerals and low energy X-ray photons are sensitively absorbed by photoelectric effects in all abundant minerals and were compared before and after the infusion of radiologic contrasts. Endogenous iron and manganese are believed to accumulate due to interactions with exogenous iodine and gadolinium in and around the infusion spots. X-ray imaging had lower sensitivity (detection limit approximately 1 part in 104), while MRI sensitivity was two orders of magnitude higher (approximately 1 part in 106), but only for paramagnetic minerals like Mn and Fe in our samples. MRI evidence of such a release of metal ions from the native pool implicates transmetallation and chelation reactions that were triggered by infused contrast agents. Since Fe and Mn play significant roles in the function of metalloenzymes, our results suggest that transmetallation and chelation could be a plausible mechanism for contrast induced toxicity in vivo.

Porphyrins as Chelating Agents for Molecular Imaging in Nuclear Medicine.

Porphyrin ligands, showing a significant affinity for cancer cells, also have the ability to chelate metallic radioisotopes to form potential diagnostic radiopharmaceuticals. They can be applied in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) to evaluate metabolic changes in the human body for tumor diagnostics. The aim of this paper is to present a short overview of the main metallic radionuclides complexed by porphyrin ligands and used in these techniques. These chelation reactions are discussed in terms of the complexation conditions and kinetics and the complex stability.

Role of fullerene carbon on tribological performance of polyimide composites at a large temperature span

The effect of fullerene carbon (C60) on the tribological performance of polyimide (PI) composites was explored at different temperature conditions. The results demonstrate the addition of 1.0 wt% C60 can greatly enhance the tribological performance of PI/1.0C60. The friction coefficients and wear rates of 0.03/0.07 and 1.0 × 10−5/1.6 × 10−5 mm3/Nm can be achieved at − 100 °C/200 °C, respectively, reducing by 86.4%/50.0% and 28.6%/30.1% compared with pure PI. It demonstrated the polymer states influenced the lubricated and loading carry capability of the sliding interfaces at different temperatures. XPS results indicated tribo-oxidation and organic-inorganic chelation reaction dominated the tribofilm growth. Moreover, molecular dynamics simulation showed the C60 enables the shear of PI easily due to the decreased intermolecular forces.

Fulvic acid-like substance-Ca(II) complexes improved the utilization of calcium in rice: Chelating and absorption mechanism

Water-soluble chelated calcium has been widely used in agriculture as a fertilizer to improve the absorption and utilization of calcium by plants. This paper prepared a new organic mineral fertilizer, based on fulvic acid-like substance chelated calcium (PFA-Ca2+ complex), using optimal parameters (i.e., pH, time, temperature, and Ca2+ concentration) to achieve a high chelation efficiency. The absorption, utilization, and distribution of the PFA-Ca2+ complex in rice roots were analyzed using laser scanning confocal microscopy (LSCM). Our results demonstrated that the optimal PFA-Ca2+ complex chelating efficiency (87%) was achieved at an initial Ca2+ concentration of 0.1 mol L−1, an equilibration time of 120 min, a pH of 5.0, and a temperature of 40 °C. The chelating reaction of a fulvic acid-like substance with Ca2+ primarily occurred on phenol hydroxyl, alcohol hydroxyl, and carboxyl groups. The PFA-Ca2+ complex was primarily enriched in the roots' pericycle, cortical, and epidermis cells, in both chelating and non-chelating forms. To our knowledge, this is the first report investigating how the PFA-Ca2+complex affects transformation in plants, which has significant implications for research on plant nutrition and nutrient distribution.

High Quantum Yield Boron and Nitrogen Codoped Carbon Quantum Dots with Red/Purple Emissions for Ratiometric Fluorescent IO4– Sensing and Cell Imaging

A facile and cost-effective hydrothermal method was developed for the preparation of boron and nitrogen codoped carbon quantum dots (B,N-CQDs) from 3-carboxyphenylboronic acid and o-phenylenediamine. The synthesized B,N-CQDs exhibit excellent properties such as excellent water solubility, strong fluorescence, good dispersion, and desirable stability. The average particle size of B,N-CQDs is 2.82 nm, and the absolute fluorescence quantum yield is 86.58%. The excitation wavelength of B,N-CQDs is 300 nm. Emission bands of B,N-CQDs appeared at 356 and 700 nm. Periodate (IO4–) quenches B,N-CQDs emissions through chelation reaction. The ratio of F356/F700 has a good linear relationship with the concentration of IO4– in the range of 0.01–40 μmol/L with the detection limit of 0.003 μmol/L. This method has the advantages of a low detection limit, high sensitivity, wide linear range, good selectivity, simplicity, and rapidness. It can be used as a ratiometric fluorescent probe for the detection of IO4–, and it was successfully applied in the analysis of IO4– in water. The cytotoxicity and biocompatibility of B,N-CQDs were evaluated and successfully applied in cell imaging.

Microwave-assisted one-pot synthesis of carbon dots for highly sensitive and selective detection of selenite

Herein, a label-free, sensitive, and selective fluorescence method for the detection of trace selenite (Se(IV)) in water sample by carbon dots (CDs) was reported. The fluorescence CDs probe was simply and rapidly synthesized within 4 min by microwave-assisted pyrolysis of citric acid and 3,3′-diaminobenzidine (DAB), with a relatively uniform size of approximately 2.6 nm. The fluorescence emission of as-prepared CDs was 450 nm upon the excitation of 400 nm with a quantum yield of about 8% against quinine sulfate as reference standard, which can be quenched by the addition of selenite. Benefit from the strong surface chelating reaction between DAB and Se(IV), the proposed sensor owned the advantage of high sensitivity (limit of detection = 0.5 ng/mL), wide linear range (1–100 ng/mL range, relative standard deviation: 3.8%), and excellent selectivity in the presence of various ions, even other forms of selenium, including selenate (Se(VI)), Selenomethionine (SeMet), and L-Selenocystine (SeCys) etc. Preliminary study on fluorescence quenching mechanism studied. The sensor was successfully exemplified for real water samples and exhibits comparative performance.

Tannic acid as an eco-friendly natural passivator for the inhibition of pyrite oxidation to prevent acid mine drainage at the source

In this study, an eco-friendly natural green polyphenol tannic acid (TA) was utilized as the passivator to inhibit pyrite oxidation. The strong coordination of phenolic hydroxyl groups in TA to Fe ions on pyrite makes TA have the characteristics of simple coating process on pyrite surface. Electrochemical measurements and chemical leaching tests were used to study the inhibition performance of TA on pyrite oxidation. The experimental results indicated that TA passivation coating could provide good antioxidant protection for pyrite and the inhibition ability of TA on pyrite oxidation raised with the increase of TA concentration. Additionally, the morphological changes of pyrite surface before and after TA passivation were further observed by Scanning electron microscopy (SEM). Finally, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to probe the interaction mechanism of TA with pyrite in detail. The results of surface analyses verified that TA was capable of forming TA-Fe complexes with Fe ions on pyrite through chelation reaction, so as to be chemically deposited on the surface of pyrite that could effectively protect pyrite from oxidation. It is believed that this work can provide a new low-cost and simple way for acid mine drainage (AMD) control.

Binding of Arsenic by Common Functional Groups: An Experimental and Quantum-Mechanical Study

Arsenic is a well-known contaminant present in different environmental compartments and in human organs and tissues. Inorganic As(III) represents one of the most dangerous arsenic forms. Its toxicity is attributed to its great affinity with the thiol groups of proteins. Considering the simultaneous presence in all environmental compartments of other common functional groups, we here present a study aimed at evaluating their contribution to the As(III) complexation. As(III) interactions with four (from di- to hexa-) carboxylic acids, five (from mono- to penta-) amines, and four amino acids were evaluated via experimental methods and, in simplified systems, also by quantum-mechanical calculations. Data were analyzed also with respect to those previously reported for mixed thiol-carboxylic ligands to evaluate the contribution of each functional group (-SH, -COOH, and -NH2) toward the As(III) complexation. Formation constants of As(III) complex species were experimentally determined, and data were analyzed for each class of ligand. An empirical relationship was reported, taking into account the contribution of each functional group to the complexation process and allowing for a rough estimate of the stability of species in systems where As(III) and thiol, carboxylic, or amino groups are involved. Quantum-mechanical calculations allowed for the evaluation and the characterization of the main chelation reactions of As(III). The potential competitive effects of the investigated groups were evaluated using cysteine, a prototypical species possessing all the functional groups under investigation. Results confirm the higher binding capabilities of the thiol group under different circumstances, but also indicate the concrete possibility of the simultaneous binding of As(III) by the thiol and the carboxylic groups.

Mn2+ Ions Capture and Uniform Composite Electrodes with PEI Aqueous Binder for Advanced LiMn2O4-Based Battery.

The electrode deterioration and capacity decay caused by the dissolution of transition metal ions have been criticized for a long time. The branched polyethyleneimine (PEI) was employed as a functional binder for spinel lithium manganese oxide (LiMn2O4, LMO) and layer structure lithium cobalt oxide (LiCoO2, LCO) to resolve the problem. Due to the chelation reaction of amine groups, PEI polymer binder can effectively absorb soluble transition metal ions, which is beneficial to reduce the loss of active materials. For PEI-based cathode, the uniform distribution of key components is achieved by the rapid curing process of water, which endow PEI-based cathode with a higher Li+ diffusion coefficient and improved electrochemical reaction kinetics. In addition, the fixed binder coating is favorable to protecting the active materials from parasitic reaction with the lithium hexafluorophosphate (LiPF6)-based electrolyte. Therefore, the PEI-based cell shows superior rate capability and long-term cycle performance. Functional binders of this study provide a simple and effective strategy to achieve higher capacity and longer cycle stability for transition metal oxide electrodes.

Ultra-long cycle H-doped VO2(B) cathode for high capacity aqueous Zn-ion battery

VO2 as a potential type of cathode material for aqueous Zn-ion batteries (AZIBs) has attracted increasing interest over the past few years, owing to the various oxidation states of vanadium and unique tunnel transport pathway. However, the major challenge for VO2 is the absence of a high-capacity and stable structure because of the slow electron transport kinetics and the collapsible crystal structure. Herein, an ultra-long life H-doped VO2 is obtained by an efficient chelation reaction with ascorbic acid (AA). Benefiting from the H-doped, the crystallinity of VO2 is reduced, and the oxygen vacancies and electron conductivity in VO2 are enhanced, which is also confirmed by the calculated results of Density Functional Theory (DFT). Based on the H-doped VO2 (AA-VO2), ultra-long 22,000 cycles at 10 A g−1 are obtained as well as high specific capacity (572 mAh g−1) and energy density (443 Wh kg−1) at 0.2 A g−1. By contrast, the AZIBs with untreated VO2 exhibit only 251 mAh g−1 specific capacity and 235 Wh kg−1 energy density. And the batteries can work no more than 2000 cycles. Therefore, this H-doped VO2 by chelation with AA is a promising cathode material for high performance aqueous zinc-ion batteries.

Sustainable Phytic Acid-Zinc Anticorrosion Interface for Highly Reversible Zinc Metal Anodes.

Although aqueous zinc-ion batteries (AZIBs) promise high capacity, low cost, and environmental friendliness, the Zn metal anode suffers from limited reversibility and unsatisfied lifespan arising from severe dendritic growth and inevitable interfacial corrosion. In this regard, constructing the artificial protective interfacial layer on the Zn metal foil has been recognized as an effective strategy to realize durable AZIBs. Inspired by the phytic acid (PA) anticorrosion conversion coating layer for industrial metal protection, herein, we designed a dense and conformal PA-Zn complex layer on the Zn anodes through a feasible, rapid wet-chemistry chelating reaction. The in situ formed uniform PA-Zn coating layer on the surface of Zn anodes can serve as a protective layer inhibiting corrosion reaction. More importantly, the desolvation energy of Zn2+ is effectively reduced by the PA-Zn layer, which gives rise to enhanced kinetics of Zn plating/stripping for uniform Zn deposition. Consequently, the PA-Zn metal anode delivered a low overpotential of 36 mV and a long lifespan over 1400 h at 2 mA cm-2 with a capacity of 1 mA h cm-2. The feasibility of PA-Zn anodes is also verified in the as-constructed PANI@V2O5||Zn full cells. This work paves the way for designing a multifunctional interface layer on Zn metal and promotes the development of high-performance AZIBs.

Fabrication of tunable hierarchical ZnO nanostructures via an anodization process

The size and morphology of nanomaterials replicate optical, electrical, and mechanical properties and their applications. In this paper, for the first time, ZnO hierarchical nanostructures were grown on Zn foil through electrochemical anodization in the presence of fluoride ions at room temperature in water/glycerol electrolyte. Fluoride ions are vital for development of chelation reactions and the formation of ZnO hierarchical nanostructures. XRD analysis confirmed the ZnO crystal phase to be wurtzite, and the Raman analysis confirmed the crystal phase to be wurtzite hexagonal. The surface morphology of ZnO reveals that the nanostructures grown on Zn foil are hierarchical nanoflowers with an even distribution. The identified binding energies from the XPS spectrum confirmed the Zn2+ state. Such unique hierarchical architectured ZnO can be used for designing high-performance optoelectronic devices such as LED lights, photodiodes, nanosensors, and solar cells.

Polypyrrole-based adsorbents for Cr(VI) ions remediation from aqueous solution: a review.

Anthropogenic activities are principally responsible for the manifestation of toxic and carcinogenic hexavalent chromium (Cr(VI)) triggering water pollution that threatens the environment and human health. The World Health Organisation (WHO) restricts Cr(VI) ion concentration to 0.1 and 0.05 mg/L in inland surface water and drinking water, respectively. The available technologies for Cr(VI) ion removal from water were highlighted with an emphasis on the adsorption technology. Furthermore, the characteristics of several polypyrrole-based adsorbents were scrutinized including amino-containing compounds, biosorbents, graphene/graphene oxide, clay materials and many other additives with reported effective Cr(VI) ion uptake. This efficiency in Cr(VI) ions adsorption is attributed to enhanced redox properties, increased number of functional groups as well as the synergistic behaviour of the materials making up the composites. The Langmuir isotherm best described the adsorption processes with maximum adsorption capacities ranging from 3.40-961.50 mg/g. The regeneration of Cr(VI) ion-laden adsorbents was studied. Ion exchange, electrostatic attractions, complexation, chelation reactions with protonated sites and reduction were the mechanisms of adsorption. Nevertheless, there are limited details on comprehensive adsorbent regeneration studies to prolong robustness in adsorption-desorption cycles and utilization of the Cr(VI) ion-laden adsorbent in other areas of research to limit the threat of secondary pollution.

Preparation of corn ACE inhibitory peptide-ferrous chelate by dual-frequency ultrasound and its structure and stability analyses

In order to improve iron chelating ability and retain the activity of functional peptide, corn peptide was chelated with iron to form corn ACE inhibitory peptide-ferrous chelate (CP-Fe) treated by dual-frequency ultrasound. Furthermore, the chelating mechanism was revealed by analyzing various structural changes, and the stability was further evaluated. Under this study condition, the iron-binding capacity of corn ACE inhibitory peptide (CP) and chelate yield reached 66.39% and 82.87%, respectively. Ultrasound-treated CP exhibited a high iron chelating ability, meanwhile, chelation reaction had no significant effect on the ACE inhibition activity (82.21%) of the peptide. CP-Fe was formed by binding the peptides amino, carbonyl and carboxyl groups with Fe2+ demonstrated by Ultra-violet spectroscopy, Fourier transform infrared characterization, X-ray diffraction, energy dispersion spectrum, zeta potential, amino acid composition and other multi-angle analyses. Moreover, ultrasound-treated CP-Fe chelate exhibited porous surface and uniform nanoparticle shape. Furthermore, ultrasound-treated CP-Fe chelate exhibited an excellent stability towards various pH (retention rate ≥ 95.47% at pH 6–10), temperatures (retention rate ≥ 85.10% at 25–70 °C), and gastrointestinal digestion (retention rate 79.18%). Overall, ultrasound-treated CP-Fe chelate possessed high iron-chelating ability, ACE inhibition activity and stability. This study provides a novel synthesis method of the iron-chelating corn ACE inhibitory peptide, which is promising to be applied as iron supplements with high efficiency, bioactivity, and stability.

Constructing zigzag-like hollow mesoporous nanospheres MoO2/C with superior lithium storage performance

Hollow mesoporous nanospheres MoO2/C are successfully constructed through metal chelating reaction between molybdenum acetylacetone and glycerol as well as the Kirkendall effect induced by diammonium hydrogen phosphate. MoO2 nanoparticles coupled by amorphous carbon are assembled to unique zigzag-like hollow mesoporous nanosphere with large specific surface area of 147.7 m2 g−1 and main pore size of 8.7 nm. The content of carbon is 9.1%. As anode material for lithium-ion batteries, the composite shows high specific capacity and excellent cycling performance. At 0.2 A g−1, average discharge capacity stabilizes at 1092 mAh g−1. At 1 A g−1 after 700 cycles, the discharge capacity still reaches 512 mAh g−1. Impressively, the composite preserves intact after 700 cycles. Even at 5 A g−1, the discharge capacity can reach 321 mAh g−1, exhibiting superior rate capability. Various kinetics analyses demonstrate that in electrochemical reaction, the proportion of the surface capacitive effect is higher, and the composite has relatively high diffusion coefficient of Li ions and fast faradic reaction kinetics. Excellent lithium storge performance is attributed to the synergistic effect of zigzag-like hollow mesoporous nanosphere and amorphous carbon, which improves reaction kinetics, structure stability and electronic conductivity of MoO2. The present work provides a new useful structure design strategy for advanced energy storage application of MoO2.

Preparation and Properties of Pearl Peptide Chelated Calcium

In order to improve the utilization of pearl, calcium supplement with high bioavailability was produced. Pearl peptide was prepared from pearl powder and chelated with calcium. The preparation process was optimized based on the chelation yield and calcium content in pearl peptide chelated calcium. The changes of chelation were compared by ultraviolet-visible absorption spectroscopy (UV-vis), fourier infrared spectroscopy (FTIR), circular dichroism (CD), X-ray diffraction (XRD), difference scanning calorimetry (DSC) and scanning electron microscopy (SEM) analysis. The results showed that pearl protein was obtained from pearl powder by acid hydrolysis and repeated centrifugation. The pearl protein was hydrolyzed by Bacillus licheniformis proteinase (BLP)to obtain pearl peptide. The final yield of pearl peptide chelated calcium was 27.24%±1.29%, and the calcium content in pearl peptide chelated calcium was 48.75%±1.20%. The structure of the pearl peptide and pearl peptide chelated calcium were then analyzed. It was found that both amino and carboxyl groups of pearl peptide were involved in the chelation reaction. And the secondary structure of pearl peptide chelated calcium changed from disordered structure to ordered and compact structure. The crystallinity increased greatly and a new substance with more stable structure was formed after the chelation reaction. And a significant aggregation was occurred in calcium-chelating peptide.

Enhanced removal of Cr(VI) and Mo(VI) from polluted water using L-cysteine doped polypyrrole/bentonite composite

The demand for clean water and soil drives high efficiency, less expensive, and eco-friendly clay-composites as adsorbents for remediation of heavy metals polluted environment. We have developed a new water remediation technique by using an organic-inorganic composite, L-cysteine doped polypyrrole modified bentonite (L-cys/PPy/BT) for removal of Cr(VI) and Mo(VI). The L-cys/PPy/BT showed maximum adsorption capacities of 318.5 and 65.4 mg/g for Cr(VI) and Mo(VI) respectively. For Cr(VI) and Mo(VI) the sorption process on L-cys/PPy/BT followed the Freundlich and Langmuir isotherm models, respectively. Furthermore, the pseudo-second-order kinetic model described the adsorption behavior of Cr(VI) and Mo(VI). Moreover, the thermodynamic parameters indicated that sorption processes were endothermic and spontaneous. Mechanistic assessment revealed that adsorption of Mo(VI) on L-cys/PPy/BT could be attributed to chelation, electrostatic attraction and ion-exchange of Mo(VI) with the imine/amine functional groups in the material's matrix, while electrostatic attraction, ion exchange, chelation and redox reaction played a significant role in the removal of Cr(VI). This research provides a new approach for the use of clay materials as potential sorbents for removal of heavy metal ions in contaminated water.

Phosphorylation modification of collagen peptides from fish bone enhances their calcium-chelating and antioxidant activity

In order to investigate the impact of phosphorylation modification on fish bone collagen peptide (CP), CP was subjected to phosphorylation modification to generate phosphorylated collagen peptide (P-CP). CP and P-CP were further chelated with calcium to form calcium-chelated collagen peptide (Ca-CP) and calcium-chelated phosphorylated collagen peptide (Ca-P-CP). The structural changes before and after phosphorylation and chelation reaction were characterized. Additionally, their stability and antioxidant activity were evaluated. The calcium-binding capacity of CP was significantly enhanced by phosphorylation, and the highest calcium-chelating capacity reached 128.21 mg/g. The introduction of phosphate ions caused esterification reaction, while the carboxyl groups, amino groups and phosphate groups of CP and P-CP were responsible for binding to calcium ions. Ca-P-CP exhibited an excellent stability (calcium retention rates >80%) towards a wide range of temperatures, pH as well as gastrointestinal digestion. Furthermore, DPPH and superoxide anion radical scavenging activities of CP and P-CP were significantly increased after chelation with calcium ions. Overall, phosphorylation modification can effectively improve the calcium-chelating ability of CP, while the resultant chelates possessed high antioxidant activity and stability. The chelates in the present study are promising to be applied as calcium supplements with high efficiency, bioactivity and stability.

Organic Ion-Associate Phase Microextraction/Back-Microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS

An ion-associate phase (IAP) microextraction/ back-microextraction system was applied for the enrichment, separation, and detection of trace amounts of nickel from environmental water samples. Thenoyltrifluoroacetone (HTTA) acted not only as a chelating reagent for nickel, but also as a component of the extraction phase, i.e., IAP. Nickel in a 40 mL sample solution was pH-adjusted with phenolsulfonate (PS−) and tetramethylammonium hydroxide and converted by chelation reaction in the presence of thenoyltrifluoroacetonate (TTA−). When benzyldodecyldimethylammonium ion (C12BzDMA+) was added, a suspension of IAP formed in the solution. The IAP consisted of TTA−, a chelating reagent, the PS−, a component of pH buffer, and C12BzDMA+, which helps extract the chelating complex. When the solution was centrifuged, the IAP separated from the suspension and the nickel-TTA chelate was extracted into the bottom phase of the centrifuge tube. After the aqueous phase was taken away, 100 µL of nitric acid (2 M) solution containing phosphate was used to back-microextract nickel from the IAP. The acid phase was measured via graphite-furnace atomic-absorption spectrometry (GF-AAS). The proposed method facilitated a 400-fold enrichment. The limit of detection was 0.02 µg L−1. The proposed method was applied for the determination of nickel in river water and seawater samples.