Preconcentration of some trace metal ions on coated alumina modified by 1-((6-(-(2-hydroxynaphthalen-1-yl)methyleneamino) hexylimino) methyl) naphthalen-2-ol

A sensitive and efficient method for preconcentration of trace amounts of some metal ions such as Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Cr³⁺, and Fe³⁺ ions based on modification of sodium-dodecyl-sulphate (SDS) coated alumina with 1-(6-(-(2-hydroxynaphthalen-1-yl) methyleneamino) hexylimino) methyl) naphthalen-2-ol (HNMAHN) is reported. The method is based on the uptake of these ions following their chelation with HNMAHN and their recovery using a suitable eluent. The influence of parameters such as pH, concentration of ligand and amount of coated alumina, SDS concentration, eluent (type and concentrations), and elution volume on metal ion recoveries are investigated. The preconcentration factor is 150 (10?mL elution volume) for a 1500?mL sample volume. The method has been successfully applied for extraction and determination of these ions content in some real samples. Extraction efficiency is generally >95% with low relative standard deviations between 1.8% and 2.4 %.     

A simple ligandless microextraction method based on ionic liquid for the determination of trace cadmium in water and biological samples

A simple and efficient ionic liquid-based ligandless microextraction method has been developed for preconcentration of cadmium ions (Cd²⁺) as a step prior to its determination by flame atomic absorption spectrometry (FAAS) with a micro-sample introduction system. In this approach, the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆] and ethanol were used as extractant and dispersive solvents to preconcentrate the Cd²⁺ in different waters, acid digested scalp hair, and nail samples. Some analytical parameters influencing the extraction efficiency of Cd²⁺ and its subsequent determination, including pH, IL volume, dispersant solvent volume, sample volume, temperature, incubation time, and matrix effect, were optimized. Under optimal conditions, the limit of detection (LOD), limit of quantification (LOQ), and enhancement factor (EF) were 0.4 μg L^?1, 1.3 μg L^?1, and 50, respectively. The relative standard deviation (RSD) of 100 μgL^?1 Cd²⁺ was 4.3% (n = 6). The validity of the proposed method was checked by determining Cd²⁺ in certified reference material (TM-25.3 fortified water) and standard addition; the results showed sufficient recovery (>98%) of Cd²⁺ within the certified value. The method was applied for preconcentration and determination of cadmium in waters and biological samples.     

Synthesis of 2,3-dihydroxynaphthalene-functionalized Amberlite XAD-4 resin: Applications for the separation and preconcentration of trace metal ions prior to their determination by inductively coupled plasma atomic emission spectrometry

A simple, sensitive column solid-phase extraction procedure for separation and preconcentration of Cu(II), Ni(II), Co(II), and Cd(II) in spiked and natural water samples using 2,3-dihydroxynaphthalene-functionalized Amberlite XAD-4 (XAD-4-DHN) chelating resin prior to their determination by inductively coupled plasma atomic emission spectrometry was discussed. The optimum experimental parameters such as pH, volume of sample and eluent, flow-rates of uptake and stripping, and sorption capacity of the chelating resin, were evaluated. The effect of the electrolytes and the cations on the preconcentration of metal ions was also investigated. The chelating resin could be reused for more than 20 cycles of sorption–desorption without any significant change (<1.0%). Recoveries obtained from this method range from 96 to 102% with R.S.D of 2.50 (n = 4). The detection limits for Cu(II), Ni(II), Co(II), and Cd(II) were found to be 1.9, 0.9, 1.2 µg, and 1.4 µg L^?1, respectively. The proposed method was applied for the determination of Cu(II), Ni(II), Co(II), and Cd(II) in spiked, tap water, and river water samples.     

Oxidized multiwalled carbon nanotubes modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole for solid phase extraction and preconcentration of some metal ions

In this work, a new procedure for the enrichment of the trace amount of Cu²⁺, Ni²⁺, Co²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions based on the utilization of multiwalled carbon nanotubes (MWCNT) modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole as chelating agent prior to their determination by flame atomic absorption spectrometry has been described. The influence of effective parameters including pH, amount of ligand and MWCNT, composition of eluent, and coexisting ions on recoveries of understudy metal ions was examined. At the optimum pH of 5.0, all metal ions were quantitatively sorbed onto the proposed solid phase and completely desorbed with 8?mL of 5.0?mol?L^?1 HNO₃. The detection limit of Cu²⁺, Co²⁺, Ni²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions was 1.7, 2.4, 2.3, 2.9, 2.8, and 1.4?µg?L^?1, while the preconcentration factor was 63 for Cu²⁺ and 94 for the other metal ions and relative standard deviations between 1.8 less than 3.0%. The proposed procedure was applied for the analysis of various samples.     

Cadmium and nickel determinations in some food and water samples by the combination of carrier element-free coprecipitation and flame atomic absorption spectrometry

A procedure for separation and enrichment of Cd(II) and Ni(II) ions based upon carrier element-free coprecipitation by using an organic coprecipitant, 2-{4-[2-(1H-Indol-3-yl)ethyl]-3-(4-methylbenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N′-(3-fluoro-phenylmethyliden) acetohydrazide, prior to their flame atomic absorption spectrometric detections has been developed. The effects of varied experimental conditions on the performance of the developed method such as pH, sample volume, amount of coprecipitating agent, etc. were evaluated in detail on the recovery of analyte ions, and the influences of some anions and cations were investigated. The limits of detection for Cd(II) and Ni(II) ions based on three times the standard deviation of the blanks (N: 10) were obtained as 0.70 μg L^?1 and 1.21 μg L^?1, respectively. The accuracy of the method was tested by analyzing a certified reference material and by spike tests. The method was applied to determine the levels of cadmium and nickel in stream and sea water, rice, red lentil, and wheat samples.     

Online solid phase preconcentration using EGDMA–MAA copolymer for lead determination by FAAS

A Ethylene glycol dimethacrylate (EGDMA) methacrylic acid (MAA) resin was used for preconcentration of lead at trace levels in water samples. For this purpose, a flow-injection, solid phase extraction method was developed for the determination of lead by flame atomic absorption spectrometry. Lead ions were sorbed on a EGDMA–MAA column at pH 4, followed by an elution step using 288 µL of 4.0 M nitric acid solution and determination by flame atomic absorption spectrometry. Optimum conditions for quantitative sorption involving the pH, sample volume, loading and elution flow rates, eluent type, and volume were investigated. A 868-fold enrichment factor could be reached. The detection limit for the water samples, estimated from the noise on the signal obtained for 250 mL of 10 µg L^?1 loaded at 4.9 mL min^?1 was 1.04 µg L^?1. The method was applied for lead determination in river water samples collected in Edirne, Turkey. Recoveries of spiked solutions (10 µg L^?1) to river water samples were quantitative. Finally, the method was validated by the analysis of certified reference material SRM 2704 (Buffalo River Sediment).     

Determination trace amounts of copper, nickel, cobalt and manganese ions in water samples after simultaneous separation and preconcentration

In the present article, a simple, rapid, sensitive and economical method has been developed for the simultaneous separation and preconcentration of the trace amounts of copper, nickel, cobalt and manganese in water samples by using modified XAD-4 resins. The sorption was quantitative in the pH range 6.0–9.0, whereas quantitative desorption occurred instantaneously with 5.0 mL of 2 M HNO₃, and selected elements have been determined by using flame atomic absorption spectrometry. Dynamic ranges were 0.04–3.5, 0.1–6.0, 0.04–4.5 and 0.04–4.0 μg/mL for copper, nickel, cobalt and manganese, respectively. The detection limits were 9.2, 28.6, 12.3 and 5.7 ng/mL for Cu(II), Ni(II), Co(II) and Mn(II), respectively. The effects of the experimental parameters, including the sample pH, eluent type, interference ions and breakthrough volume, were studied for separation and preconcentration of Cu(II), Ni(II), Co(II) and Mn(II) ions. Determination of these ions in standard samples confirmed that the proposed method has good accuracy. The proposed method was used for the determination of these ions in water samples.     

Thermodynamics of chromium(III) adsorption onto a cation exchanger derived from saw dust of Jack wood

A novel cation exchanger, polymethacrylic acid-grafted saw dust (SD) with spacer group (SP) containing carboxylate functional group at the chain end (SDGPMA-SP-COOH) was prepared from saw dust of Jack wood, and its adsorption equilibrium and thermodynamics of Cr(III) ions were studied at different initial concentrations and temperatures at pH 7.0 using batch technique. Thermodynamic parameters such as change in standard free energy, ΔG ⁰, standard enthalpy, ΔH ⁰ and standard entropy, ΔS ⁰ were determined. The values of isosteric heat of adsorption (ΔH _x ) remain constant at different surface loading of Cr(III) indicating homogeneous surface sites and the absence of lateral interaction between adsorbed ions.     

Application of Zr(IV) tungstate for removal of metal ions from aqueous solutions

A heteropolyacid Zr(IV) tungstate-based cation exchanger has been synthesized. An amorphous sample, prepared at pH 1.2 and having a Na⁺ ion exchange capacity of 0.92?meq?g^?1, was selected for further studies. Its physicochemical properties were determined using Fourier transform infrared spectrometer, X-ray diffraction, thermogravimetric, and scanning electron studies. To understand the cation exchange behavior of the material, distribution coefficients (K _d) for metal ions in various solvent systems were determined. Some important binary separations of metal ions, namely Mg²⁺–Bi³⁺, Cd²⁺–Bi³⁺, Fe³⁺–Bi³⁺, Th⁴⁺–Bi³⁺, and Fe³⁺–Zn²⁺, were achieved on such columns. The practical utility of these separations was demonstrated by separating Fe³⁺ and Zn²⁺ ions quantitatively in commercial pharmaceutical formulation. The cation exchanger has been successfully applied also for the treatment of industrial wastewater and a synthetic mixture. All the results suggests that Zr(IV) tungstate has excellent potential for the removal of metals from aqueous systems using packed columns of this material.     

Amberlite XAD-7 impregnated with morpholine dithiocarbamate as trace metal extractant

Application of Amberlite XAD-7 impregnated with morpholine dithiocarbamate (MDTC) for separation and preconcentration of trace amounts of lead, copper, cobalt, iron, nickel, cadmium and zinc and determination by ICP-AES has been described. The optimum experimental parameters, such as pH, sample flow rate, eluent and effect of matrix ions on the preconcentration were investigated. Simultaneous enrichment of the seven metals was accomplished. The t _1/2 values for sorption are 2.9, 3.3, 3.7, 3.6, 2.8, 4.1 and 2.8 respectively for Pb(II), Cu(II), Co(II), Fe(III), Ni(II), Cd(II) and Zn(II). The method was applied for the determination of trace metal ions in seawater and natural water samples. The results have been compared with extraction GFAAS method.     

Electrochemical hydride generation of tin(II) and its determination by electrothermal atomic absorption spectrometry with in situ trapping in the graphite tube atomizer

An electrolytic hydride generation system for the determination of tin(II) by means of batch electrochemical hydride generation-electrothermal atomic absorption spectrometry (EcHG-ETAAS) with in situ trapping in a graphite tube atomizer is described. The effects of four permanent chemical modifiers – palladium, tungsten, iridium, and platinum – for graphite tube treatment on analyte absorbance and the effects of four cathode materials, i.e., Pb, Sn, Pb–Sn alloy, and glassy carbon, are checked. Three electrolytes, i.e., nitric acid, sulfuric acid, and hydrochloric acid, are examined as catholyte solutions. The influence of several parameters on EcHG is investigated using multivariate and univariate methods. Interferences of some concomitant ions are evaluated. The calibration curve is linear from 1 to 200?µg?L^?1, with a detection limit of 0.8?µg?L^?1 and a relative standard deviation of 6.2% (n?=?3) for 100?µg?L^?1 Sn(II). The proposed method was successfully applied in the analysis of real environmental water samples and reference materials, and good spiked recoveries over the range of 93.1–115% were obtained. The proposed technique provides a means for developing hydride generation of other elements.     

Synthesis and characterization of an ion exchanger based on tamarind kernel powder and its application for removal of some metal ions from industrial effluents

A resin synthesized from tamarind kernel powder possesses high selectivity for metal ions. Distribution coefficients for some metal ions has been determined by the batch method. The influence of pH on ion exchange capacity and K _d value of metal ions were studied. The resin has been characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, chemical composition and ion exchange capacity (IEC). The selectivity order is Pb²⁺?>?Cu²⁺?>?Fe²⁺?>?Zn²⁺?>?Ni²⁺. Removal of metal ions from the aqueous solution and from effluents of a steel mill has been studied.     

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.     

Solid phase extraction of trace metals from environmental samples using Amberlite XAD-7 loaded with 2-hydroxy-propiophenone-4-phenyl-3-thiosemicarbazone and determination by inductively coupled plasma–atomic emission spectrometry

A method for the solid phase extraction of trace metals, namely Co, Cu, Pb, Ni and Zn, from environmental and biological samples using column Amberlite XAD-7 loaded with 2-hydroxy-propiophenone-4-phenyl-3-thiosemicarbazone (HPPPTSC) and determination by inductively coupled spectrometry (ICP–AES) has been developed. The reagent has the capacity to form chelate complexes with the metals because of three binding sites in the reagent molecule. The optimum experimental conditions for the quantitative sorption of five metals, pH, effect of flow rate, concentration of eluent, sorption capacity and the effect of diverse ions on the preconcentration of analytes have been investigated. The sorption capacity of the resin has 83, 127, 35, 88 and 85?µmol?g^?1 for Co²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Zn²⁺, respectively. The preconcentration factors for Co²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Zn²⁺ were 100, 110, 120, 140 and 150, respectively. The accuracy of the proposed procedure was evaluated by standard reference materials. The achieved results were in good agreement with certified values. The proposed method was applied for the determination of trace metals in river water and plant leaves.     

Ligand-less in situ surfactant-based solid phase extraction for preconcentration of silver from natural water samples prior to its determination by atomic absorption spectroscopy

A simple and rapid ligand-less in situ surfactant-based solid phase extraction method for preconcentration of silver from water samples is developed. In this method, a cationic surfactant containing a proper alkyl group (n-dodecyltrimethylammonium bromide) is dissolved in the aqueous sample and then a proper ion-pairing agent (ClO₄^?) is added. Due to the interaction between surfactant and ion-pairing agent, solid particles are formed and used for adsorption of silver carbonate. After centrifugation, the sediment is dissolved in 2.0 mL 1 M HNO₃ in ethanol and then aspirated directly into the flame atomic absorption spectrometer. Variables affecting the extraction efficiencies such as pH, concentrations of surfactant and CO₃^2?, ion pair concentration, and extraction time, are optimized. Under such conditions, the calibration curve is linear from 3 to 700 μg L^?1. Detection limit is 1.1 μg L^?1 with an enrichment factor of 37. The relative standard deviation for eight replicate measurements of 100 μg L^?1 is 2.1%. The method has been applied for the determination of silver in water samples.     

Effects of calcium,strontium, and magnesium on the coccolithophorid Cricosphaera (Hymenomonas) carterae. I. Calcification

The present investigation concerns the effects of calcium, strontium, and magnesium on calcification and mineralogy of the calcified bodies (coccoliths) of the coccolithophorid Cricosphaera (Hymenomonas) carterae. The capacity of cells to calcify in various concentrations of these ions was examined following preliminary decalcification in CO₂. At a concentration of 10^-2 M Ca, 75% of the cells formed coccoliths within 24 h and almost all cells were recalcified after 2 days. At 10^-3 or 10^-4 M Ca no recalcification occurred. However, with the addition of Sr to the Ca-deficient media, calcification took place as shown by observations of coccoliths and by analysis of Ca. The percentage of calcified cells increased with increasing concentrations of Sr. Strontium added to a Ca-deficient media was much more effective than an equivalent concentration of Ca. No Sr was deposited in the coccoliths. X-ray analysis demonstrated that calcite was deposited by cells in all concentrations of Ca and Sr at which calcification took place. At concentrations of Mg in the media from O. O to 4.2×10^-2 M, the cells retained their ability to calcify, although calcification was markedly reduced in the absence of Mg. In low Mg concentrations (1.3×10^-4 and 4.2×10^-6 M), the coccoliths were 60% calcite and 40% aragonite, and in teh absence of Mg, only calcite was formed.     

全氟辛烷磺酸盐(PFOS)替代品对4种本土水生生物的生态毒性

本文选择了紫背浮萍、四尾栅藻、蚤状溞和稀有鮈鲫4种本土水生生物,开展了阳离子表面活性剂、织物三防整理剂、C4三防整理剂和C6三防整理剂4种全氟辛烷磺酸盐(PFOS)替代品的安全性评估,为筛选理想PFOS化学替代品提供科学依据。急性毒性结果发现阳离子表面活性剂对4种水生生物均未显示出急性毒性;织物三防整理剂、C4三防整理剂和C6三防整理剂对蚤状溞的LC50值分别为17.97、64.61和85.58 mg·L-1,显示出低的急性毒性。另外,织物三防整理剂对四尾栅藻的半数抑制浓度(EC50)值为88.32 mg·L-1,而对稀有鮈鲫半致死浓度(LC50)值为14.79 mg·L-1,均存在急性毒性。短期生长抑制试验结果发现阳离子表面活性剂、织物三防整理剂、C4三防整理剂和C6三防整理剂对稀有鮈鲫生长抑制最低可见效应浓度(LOEC)值分别为20、1.5、100和50 mg·L-1,表明4种PFOS替代品均显示低慢性毒性。急慢性综合分析可知C4和C6三防整理剂相对较安全,可能成为理想的PFOS替代品。     

A novel ligand for cloud point extraction to determine gold content in ore samples

Gold is a valuable metal occurring usually at very low concentrations in complex natural samples. Gold analysis thus needs preconcentration methods. Classical liquid–liquid extraction involves hazardous organic solvents. Alternatively, cloud point extraction involves non-toxic and nonvolatile surfactants. Here, we analyzed ore samples. The complex of Au(III) with sulphapyridylazo resorcin was extracted by the cloud point method. Concentrations were measured by flame atomic absorption spectrometry. We tested the effects of pH, reagent concentration, Triton X-100 surfactant concentration, equilibration temperature and time. Results show that the best detection limit of the method was 0.48 µg L^?1 for Au with a preconcentration factor of 31 times. Calibration is linear in range of 6.4–2,000 µg L^?1, and relative standard deviations are lower than 5 %. Quantum chemical computations reveal the plausible structure of the gold–ligand complex. This report represents the first determination of gold using sulphapyridylazo resorcin as a ligand.     

全氟辛烷磺酸盐(PFOS)对土壤跳虫的生态毒性

将两种跳虫(Folsomia candida和Folsomia fimetaria)暴露在全氟辛烷磺酸盐(perfluorooctane sulfonate,PFOS)污染的人工土壤中,利用跳虫存活数量、繁殖数量与回避行为来评价PFOS对跳虫的生态毒性。结果表明,PFOS对F.candida和F.fimetaria急性毒性的LC50(7d)分别为4777和2219mg·kg-1,慢性毒性的EC50(28d)分别为0.13和0.05mg·kg-1。此外,PFOS对两种跳虫回避行为影响的EC50(48h)分别为0.51mg·kg-1(F.candida)和0.31mg·kg-1(F.fimetaria)。分析比较发现,PFOS对跳虫急性死亡率影响很小,但对跳虫的回避行为和繁殖率有显著影响,可用来表征土壤中PFOS的生态毒性,且选用有性生殖的F.fimetaria及其慢性毒性实验来评价土壤中PFOS的毒性相对最灵敏。     

Nitrogen fixation (acetylene reduction) in the phyllosphere of Thalassia testudinum

N₂ fixation (C₂H₂ reduction) associated with the leaves of the sea grass Thalassia testudinum was investigated at 5 sites in South Florida (Biscayne Bay) and one site in the Bahamas (Bimini Harbor). Significant activities were correlated with the occurrence of a heterocystous blue-green alga (Calothrix sp.) on the leaves. C₂H₂ reduction was not stimulated by organic compounds, either aerobically or anaerobically in the light or dark. Therefore, other physiological types of microbes were not important in N₂ fixation. Diurnal and seasonal variations in N₂ fixation occurred, with maximal rates during the daytime and in the late spring and early summer. N₂ fixation was negligible at four stations in Biscayne Bay. At the fifth station, near Fowey Rock, about 5 kg N ha^-1 year^-1 was fixed. In the summer, the N₂ fixed per day (4–5 mg N m^-2) could provide 4 to 23% of the foliar productivity demands of T. testudinum at this site and the station in Bimini Harbor. N₂ fixation at the periphery of a sea-grass patch, near Fowey Rock, could provide 8 to 38% of the daily nitrogen requirement for leaf production, and thereby might compensate for a less effective trapping and recycling of nitrogen from dead leaves in such regions.