Silver nanoparticle loaded on activated carbon and activated carbon modified with 2-(4-isopropylbenzylideneamino)thiophenol (IPBATP) as new sorbents for trace metal ions enrichment

The efficiencies and performances of silver nanoparticle loaded activated carbon modified with 2-(4-isopropylbenzylideneamino)thiophenol (IPBATP-Ag-NP-AC) and activated carbon modified with IPBATP (IPBATP-AC), as new sorbents, were evaluated for separation and preconcentration of Cu²⁺, Zn²⁺, Co²⁺, Cd²⁺ and Pb²⁺ ions from real environmental samples. The retained metals content was reversibly eluted using 5?mL of CH₃COOH (6.0?mol?L^?1) and/or 10?mL of 4.0?mol?L^?1 HNO₃ for IPBATP-Ag-NP-AC and IPBATP-AC, respectively. The experimental parameters influence the recoveries of metal ions including pH, amounts of ligand and supports, condition of eluents, sample and eluent flow rates of has been investigated. The preconcentration factors were found to be 100 for Zn²⁺, Cd²⁺, Co²⁺, Cu²⁺ and 50 for Pb²⁺ ions using IPBATP-Ag-NP-AC, and 50 for Zn²⁺, Cd²⁺, Co²⁺, Cu²⁺ and 25 for Pb²⁺ ions using IPBATP-AC. The detection limit of both SPE-based sorbents was between 1.6–2.5?ng?mL^?1 for IPBATP-AC and 1.3–2.5?ng?mL^?1 for IPBATP-Ag-NP-AC. The proposed methods have been successfully applied for the extraction and determination of the understudy metal ions content in some real samples with extraction efficiencies higher than 90% and relative standard deviations (RSD) lower than 2.4%.     

Solid phase extraction of heavy metals on chemically modified silica-gel with 2-(3-silylpropylimino) methyl)-5-bromophenol in food samples

Trace amounts of Fe³⁺, Pb²⁺, Cu²⁺, Ni²⁺, Co²⁺ and Zn²⁺ ions were efficiently enriched following complexation with silica-gel chemically functionalized with 2-((3-silylpropylimino)methyl)-5-bromophenol. The enriched metal ions efficiently eluted with 6?mL of 4.0?mol?L^?1 nitric acid and their metal contents were determined by flame atomic absorption spectrometry (FAAS). The influences of the analytical parameters and experimental variables on the recoveries of the metal ions under study were investigated and optimized. The method has high sorption preconcentration efficiency even in the presence of various interfering ions. At optimum values of all variables the method is applicable for analysis of real samples with recoveries in the range of 95 to 105% with RSD lower than 4.2% and detection limits between 1.4 and 2.8?µg?L^?1.     

Anthroneamine based chromofluorogenic probes for Hg2+ detection in aqueous solution

Anthroneamine derivatives 1–3 (H₂O:DMSO; 9:1, HEPES buffer, pH 7.0 ± 0.1) undergo highly selective fluorescence quenching with Hg²⁺. The observed linear fluorescence intensity change allows the quantitative detection of Hg²⁺ between 200 nM/40 ppb—12 μM/2.4 ppm even in the presence of interfering metal ions viz. Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Cr³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, Pb²⁺. Probes 1–3 and their Hg²⁺ complexes also show the broad pH resistance for their practical applicability.     

Improvement in performance of a flow electrochemical sensor by using carbamoyl-arms polyazamacrocycle for the preconcentration of lead ions onto the electrode

A flow electrochemical sensor for trace analysis of lead, using TETRAM-modified graphite felt electrode is reported here. TETRAM ligands are covalently immobilized on the graphite felt by chemical reactions on amino acid linkers, previously attached to the electrode by an electrochemical process. The detection is performed in two steps: the preconcentration of Pb²⁺ ions by complexation with immobilized TETRAM and the analysis by linear sweep stripping voltammetry. A calibration curve typical of at least two equilibrium processes is obtained. A limit of detection of 2.5 × 10^?8 mol L^?1 is reached for a total analysis time of 35 min. Interestingly, the flow sensor shows a good selectivity toward lead in presence of Cu²⁺, Cd²⁺, Ni²⁺, Zn²⁺ and Co²⁺ ions. This new sensor exhibits improved sensitivity and selectivity compared to the previously reported sensor using cyclam-modified electrode. It is stable after three uses, using strong acidic medium for the regeneration step.     

Spectrophotometric and conductometric studies of the thermodynamics complexation of Zn2+, Ni2+, Co2+, Pb2+ and Cu2+ ions with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane ligand in acetonitrile solution

The complexation reaction between 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane ligand (Kryptofix5) and Zn²⁺, Ni²⁺, Co²⁺, Pb²⁺ and Cu²⁺ ions were studied conductometrically in acetonitrile solution. The formation constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance and absorbance measurements in various mole ratios. The enthalpy and entropy changes of the complexation reactions were derived from titration conductometry in acetonitrile at various temperatures. At 25 °C, the stability of the resulting complexes varied in the order Pb²⁺ > Zn²⁺ > Cu²⁺> Co²⁺> Ni²⁺.     

A chelating resin with bis[2-(2-benzothiazolylthioethyl)sulfoxide]: Synthesis, characterization and properties for the removal of trace heavy metal ion in water samples

A new chelating resin containing bis[2-(2-benzothiazolylthioethyl)sulfoxide] was synthesized using chloromethylated polystyrene as material and characterized by elemental analysis and infrared spectra. The adsorption capacities of the newly formed resin for Hg²⁺, Ag⁺, Cu²⁺, Zn²⁺, Pb²⁺, Mn²⁺, Ni²⁺, Cd²⁺ and Fe³⁺ were investigated over the pH range 1.0-6.0. The resin exhibited no affinity for alkali or alkaline earth metal ions. The maximum adsorption capacities of the resin for Hg²⁺, Ag⁺, Cu²⁺, Zn²⁺, Pb²⁺, Mn²⁺, Ni²⁺, Cd²⁺ and Fe³⁺ were 1.49, 0.96, 0.58, 0.11, 0.37, 0, 0.24, 0.36 and 0.25 mmol g⁻¹, respectively. In column operation it had been observed that Hg²⁺ and Ag⁺ in trace quantity could be separated from different binary mixtures and Hg²⁺ could be effectively removed from industrial wastewater and the natural water spiked with Hg²⁺ at usual pH.     

Thermal and ion-exchange studies on chelating terpolymer resins derived from o cresol urea formaldehyde

Terpolymers prepared by condensation of o cresol and urea with formaldehyde in presence of acid catalyst (2 M HCl) proved to be selective chelating ion exchange resins for certain metal ions. The molecular weights of the synthesised terpolymers were determined by GPC Technique. TGA analysis was employed to study the thermal stability and the kinetic data like activation energy of the terpolymer resins. Chelation ion exchange properties of these terpolymers were studied for Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺ ions. A batch equilibrium method was employed in the study of the selectivity of metal ion uptake involving the measurements of distribution of a given metal ion between the polymer samples. The study was carried out over a wide pH range and in media of various ionic strengths.     

Human health risk assessment of heavy metals via consumption of contaminated vegetables collected from different irrigation sources in Lahore,Pakistan

Soil pollution with heavy metals due to discharge of untreated urban and industrial wastewater is a major threat to ecological integrity and human well-being. The presenting study aimed to determine human health risks associated via food chain contamination of heavy metals routing from irrigation of urban and industrial wastewater. Irrigated water, soil and vegetables were analyzed for Cr²⁺, Co²⁺, Ni²⁺, Cu²⁺, Pb²⁺, Cd²⁺, Mn²⁺ and Zn²⁺; transfer factor (TF), daily intake of metals (DIM) and health risk index (HRI) were also calculated. Cr²⁺, Pb²⁺ and Cd²⁺ in vegetables cultivated by wastewater exceeded the permissible limits (European Union, 2002) while TF was lower for all metals except Co²⁺ and HRI was found to be maximum for Spinacia oleracea (2.42 mg/kg) and Brassica campestris (2.22 mg/kg) cultivated by wastewater. S. oleracea, B. campestris, Coriandrum sativum posed a severe health risk with respect to Cd and Mn.     

Competitive adsorption of toxic heavy metal contaminants by gum kondagogu (Cochlospermum gossypium): A natural hydrocolloid

Gum kondagogu (Cochlospermum gossypium), a naturally occurring tree biopolymer, is exploited as a biosorbent to remove metal ions from aqueous solutions. The removal efficiency of toxic metals by gum kondagogu was determined quantitatively in the order Cd²⁺ > Cu²⁺ > Fe²⁺ > Se²⁺ > Pb²⁺ > total Cr > Ni²⁺ > Zn²⁺ > Co²⁺ > As²⁺ at pH 5.0 ± 0.1 and temperature 25 ± 2 °C by inductively coupled plasma-mass spectrometry (ICP-MS). The biosorption (%) of various metal ions tested was found to be in the range of 97.3–16.7%, at pH 5.0. The morphological and mechanisms of interaction of toxic metal ions with gum kondagogu were assessed by scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM-EDXA) and X-ray diffraction (XRD) spectrum. The analysis indicated that biosorption process included morphological changes, precipitation, complexation and ion exchange mechanism for the removal of metal ions by the gum. XRD analysis indicated the amorphous nature of gum kondagogu, which facilitate metal biosorption. The metal ions adsorption leads to its deposition on the gum kondagogu matrix in a crystalline state.     

Synthesis and characterization of 2-(5-Bromo-2-Pyridylazo)-5-[(N,N-dicarboxylmethyl) amino]- phenol as a water-soluble chromogenic reagent

A new water soluble chromogenic reagent, 2-(5-bromo-pyridylazo)-5-[(N,N-dicarboxylmethyl)amino]-phenol has been synthesized. Its colour reaction with various metal ions was tested, and the acid dissociation constant of the reagent, and the stability constants of the chelates of Ni²⁺, Co²⁺, Cu²⁺, Mn²⁺, Pb²⁺, Zn²⁺ and UO ₂ ²⁺ were determined. The application of the reagent to spectrophotometric determination of nickel in irons is presented.     

Quenching effect of some heavy metal ions on the fast peroxyoxalate-chemiluminescence of 1-(dansylamidopropyl)-1-aza-4,7,10-trithiacyclododecane as a novel fluorophore

The fast chemiluminescence (CL) arising from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of 1-(dansylamidopropyl)-1-aza-4,7,10-trithiacyclododecane (L) as a novel fluorophore, and imidazole as catalyst, has been studied in ethyl acetate solution. The relationships between the chemiluminescence intensity and concentrations of TCPO, imidazole, hydrogen peroxide and L are reported. In the presence of imidazole as catalyst, the entire CL signal was completed in less than 3 s. The quenching effect of Cu²⁺, Pb²⁺, Cd²⁺, Hg²⁺ and Ag⁺ ions on the chemiluminescent system was investigated, the resulting Stern–Volmer plots were obtained and the K_Q values were calculated. It was found that the quenching effect of metal ions on the chemiluminescence of L decreases in the order Cu²⁺ > Pb²⁺ > Cd²⁺ > Hg²⁺ > Ag⁺.     

Thermodynamic studies on complexation of divalent transition metal ions with some zwitterionic buffers for biochemical and physiological research

The interaction between the zwitterionic buffers (3-[N-bis(2-hydroxyethyl)amino]-2-hydroxy propane sulfonic acid, N-(2-actamido)-2-aminoethane sulfonic acid, and 3-[(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxy propane sulfonic acid) with some divalent transition metal ions (Cu^II, Ni^II, Co^II, Zn^II, and Mn^II) were studied at different temperatures (298.15 to 328.15) K at ionic strength I = 0.1 mol · dm⁻³ NaNO₃ and in the presence of 10%, 30%, and 50% (w/w) dioxene by using potentiometry. The thermodynamic stability constants were calculated as well as the free energy change for the 1:1 binary complexation. The protonation constants of the zwitterionic buffers were also determined potentiometrically under the above conditions.     

Transition metal-chelating surfactant micelle templates for facile synthesis of mesoporous silica nanoparticles

Highly ordered mesoporous silica nanoparticles with tunable morphology and pore-size are prepared by the use of a transition metal-chelating surfactant micelle complex using Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ ions. These metal ions formed a metal-P123 micelle complex in an aqueous solution, while the metal ions are chelated to the hydrophilic domain such as the poly(ethylene oxide) group of a P123 surfactant. The different complexation abilities of the utilized transition metal ions play an important role in determining the formation of nano-sized ordered MSNs due to the different stabilization constant of the metal-P123 complex. Consequently, from a particle length of 1700 nm in the original mesoporous silica materials, the particle length of ordered MSNs through the metal-chelating P123 micelle templates can be reduced to a range of 180–800 nm. Furthermore, the variation of pore size shows a slight change from 8.8 to 6.6 nm. In particular, the Cu²⁺-chelated MSNs show only decreased particle size to 180 nm. The stability constants for the metal-P123 complex are calculated on the basis of molar conductance measurements in order to elucidate the formation mechanism of MSNs by the metal-chelating P123 complex templates. In addition, solid-state ²⁹Si, ¹³C-NMR and ICP-OES measurements are used for quantitative characterization reveal that the utilized metal ions affect only the formation of a metal-P123 complex in a micelle as a template.     

A novel ion-imprinted nanocomposite for selective separation of Pb2+ ions

In this study, the ion-imprinting method has been integrated to develop a novel composite material for the selective separation of Pb²⁺ ions. Also, Pb²⁺ ion binding ability of the organosmectite based inorganic-organic composite incorporation of bicyclic C18 organic compound into smectite layers was conducted to draw a projection its potential use as a solid phase exchanger which is quite selective toward Pb²⁺ ions. The ion-imprinted nanocomposites were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), swelling tests, and elemental analyses. After that, maximum binding capacity, pH, and equilibrium binding time were also been optimized. In order to show the selectivity of the composite synthesized, non-imprinted composites were also synthesized in absence of Pb²⁺ ions during polymerization. In this step, Ni²⁺, Co²⁺, Al³⁺, Zn²⁺, and Cu²⁺ ions were used as competitors under batch adsorption conditions. The relative selectivity coefficients of imprinted composite were calculated as 28.5, 156.5, 69.3, 24.8 and 131.6 for Pb²⁺/Co²⁺, Pb²⁺/Cu²⁺, Pb²⁺/Al³⁺, Pb²⁺/Zn²⁺, Pb²⁺/Ni²⁺ binary solutions, respectively. Finally, reusability of the composites was evaluated to show its cost-efficiency by repeating adsorption-desorption experiments ten-times. The adsorption capacity of the imprinted composites did not change significantly whereas that of non-imprinted version reduced dramatically.     

Co(II), Ni(II), Cu(II) and Zn(II) complexes of aminothiazole‐derived Schiff base ligands: Synthesis,characterization, antibacterial and cytotoxicity evaluation,bovine serum albumin binding and density functional theory studies

Transition metal complexes of type M(L)₂(H₂O)_x were synthesized, where L is deprotonated Schiff base 2,4‐dihalo‐6‐(substituted thiazol‐2‐ylimino)methylphenol derived from the condensation of aminothiazole or its derivatives with 2‐hydroxy‐3‐halobenzaldehyde and M = Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ (x = 0 for Cu²⁺ and Zn²⁺; x = 2 for Co²⁺ and Ni²⁺). The synthesized Schiff bases and their metal complexes were thoroughly characterized using infrared, ¹H NMR, electronic and electron paramagnetic resonance spectroscopies, elemental analysis, molar conductance and magnetic susceptibility measurements, thermogravimetric analysis and scanning electron microscopy. The results reveal that the bidentate ligands form complexes having octahedral geometry around Co²⁺ and Ni²⁺ metal ions while the geometry around Cu²⁺ and Zn²⁺ metal ions is four‐coordinated. The geometries of newly synthesized Schiff bases and their metal complexes were fully optimized in Gaussian 09 using 6–31 + g(d,p) basis set. Fluorescence quenching data reveal that Zn(II) and Cu(II) complexes bind more strongly to bovine serum albumin in comparison to Co(II) and Ni(II) complexes. The ligands and their complexes were evaluated for in vitro antibacterial activity against Escherichia coli ATCC 25922 (Gram negative) and Staphylococcus aureus ATCC 29213 (Gram positive) and cytotoxicity against lever hepatocellular cell line HepG2.     

Simultaneous determination of metal ions as complexes of pentamethylene dithiocarbamate in Indus river water,Pakistan

River water samples before and after mixing with industrial effluents were collected at an interval of 4 weeks for one year and analyzed for simultaneous determination of Fe³⁺, Cr³⁺, Mn²⁺, Cu²⁺, Ni²⁺and Co²⁺ after preconcentration using pentamethylene dithiocarbamate (PMDTC) as derivatizing reagent and subsequent solvent extraction by high performance liquid chromatography (HPLC). The average levels (n = 12) of metal ions were found in the range of 14.2–542 μg/L. The results were then compared with a standard flame atomic absorption spectrophotometric method revealed no significant differences.     

1-(d-Glucopyranosyl-2′-deoxy-2′-iminomethyl)-2-hydroxynaphthalene as chemo-sensor for Fe in aqueous HEPES buffer based on colour changes observable with the naked eye

A new glucose-based C2-derivatized colorimetric chemo-sensor (L₁) has been synthesized by a one-step condensation of glucosamine and 2-hydroxy-1-naphthaldehyde for the recognition of transition metal ions. Among the eleven metal ions studied, viz., Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Hg²⁺, L₁ results in visual colour change only in the presence of Fe²⁺, Fe³⁺and Cu²⁺ in methanol. However, in an aqueous HEPES buffer (pH 7.2) it is only the Fe³⁺ that gives a distinct visual colour change even in the presence of other metal ions, up to a concentration of 280 ppb. The changes have been explained based on the complex formed, and the composition has been determined to be 2:1 between L₁ and Fe³⁺ based on Job’s plot as well as ESI MS. The structure of the proposed complex has been derived based on HF/6-31G calculations.     

A Schiff base fluorescence probe for highly selective turn-on recognition of Zn2+

A simple Schiff base CTS, synthesized between 2-hydroxy-1-naphthaldehyde and 2-benzylthio-ethanamine, was found to be a good turn-on fluorescence probe for the detection of Zn²⁺, due to the restriction of the rotation of the bond between CN and naphthalene ring and/or the blocking of the photo-induced electron transfer (PET) mechanism of the nitrogen atom to naphthalene ring. Excellent selectivity for Zn²⁺ was evidenced, over many other competing ions, including Fe³⁺, Cr³⁺, Ni²⁺, Co²⁺, Fe²⁺,Mn²⁺, Ca²⁺, Hg²⁺, Pb²⁺, Cu²⁺, Mg²⁺, Ba²⁺, Cd²⁺, Ag⁺, Li⁺, K⁺, and Na⁺, in EtOH/HEPES buffer (95:5, v/v, pH = 7.4). It was noteworthy that Cd²⁺ had no interference with Zn²⁺. The stoichiometric complex of CTS-Zn²⁺ was determined to be 2:1 for CTS and Zn²⁺ in molar, based on the Job plot and single crystal X-ray diffraction data. The binding constant of the complex was 85.7 M^?2 with a detection limit of 5.03 × 10^?7 M. The fluorescence bio-imaging capability of CTS to detect Zn²⁺ in live cells was also studied. These results indicated that CTS could serve as a favorable probe for Zn²⁺.     

Complex formation between manganese(II), cobalt(II), nickel(II), copper(II) and a series of new ligands derived from N,N′-O-phenylenebis(salicylideneimine)

A series of new ligands derived from N,N′-O-phenylenebis(salicylideneimine) have been synthesized and characterized by spectrometric methods. Their protonation constants and the stability constants of their complexes with Mn²⁺, Co²⁺, Ni²⁺ et Cu²⁺ have been determined by potentiometric methods in a water–ethanol (90:10 v/v) mixture at a 0.2 mol l⁻¹ ionic strength (NaCl) and at 25.0 ± 0.1 °C. The Sirko program was used to determine the protonation constants as well as the binding constants of both species [M(HL)]⁺ and [ML]. The stability order obtained is in agreement with Irving–Williams series.