Solvent extraction of some trace metals and iron with <Emphasis Type="Italic">N</Emphasis>-Octyl-<Emphasis Type="Italic">N,N</Emphasis>-bis(dihexylphosphinylmethyl)amine

The processes were studied of the solvent extraction of the ions of triply-charged trace elements including scandium, indium, gallium, and yttrium, as well as iron, with N-octyl-N,N-bis(dihexylphosphinylmethyl) amine solution in toluene, chloroform or methylene chloride from hydrochloric, nitric or perchloric acids aqueous solutions. The metals extraction dependence on the acid concentration showed that the best results were reached using perchloric acid. The calculation of partition coefficients of metals allowed us to reveal a high selectivity of the scandium extraction. The prospects of using the investigated bisphosphinylamine in the technology of extraction, concentration and separation of the trace metals ions was concluded.     

Flame atomic absorption spectrometric determination of μg amounts of Fe (III) ions after solid phase extraction using modified octadecyl silica membrane disks

A simple, rapid and reliable method has been developed to selectively separate and concentrate ultra trace amounts of Fe (III) ions from aqueous samples for the measurement by flame atomic absorption spectrometry (FAAS). By the passage of aqueous samples through an octadecyl silica membrane disk modified by a recently synthesized Schiff base (Bis-(4-nitro phenyl azo) salisilidine-1,3-diamino propane), Fe(III) ions adsorb quantitatively and most of matrix elements will pass through the disk to drain. The retained iron ions are then stripped from the disk by minimal amount of 0.1 mol l^− 1 sulfuric acid as eluent. Extraction efficiency and the influence of pH, flow rates, amount of ligand, type and least amount of stripping acid as eluent were evaluated. The recovery of the iron from aqueous solution on the membrane disk modified with 3 mg Schiff's base was quantitative over pH 2–4.5.     

Solid phase extraction and determination of lead in soil and water samples using octadecyl silica membrane disks modified by bis[1-hydroxy-9,10-anthraquinone-2-methyl]sulfide and flame atomic absorption spectrometry

A simple, reliable and relatively fast method has been developed to selectively separate and concentrate trace amounts of lead from aqueous samples for the measurement by flame atomic absorption spectrometry. By the passage of aqueous samples through an octadecyl-bonded silica membrane disk modified by a recently synthesized bis(anthraquinone)sulfide, Pb(2+) ions adsorb quantitatively and almost all matrix elements will pass through the disk to drain. The retained lead ions are then stripped from the disk by minimal amount of acetic acid as eluent. The proposed method permitted large enrichment factors of about 300 and higher. The limit of detection of the proposed method is 50 ng Pb(2+) per 1000 ml. The effects of various cationic interferences on the recovery of lead in binary mixtures were studied. The method was successfully applied to the determination of lead in soil and water samples.     

Determination of trace elements Cd,Co, Mo,Se, Ti and V in natural waters by neutron activation analysis

The concentration of cadmium, cobalt, molybdenum, selenium, titanium and vanadium in natural water was determined by neutron activation analysis, using a prior preconcentration by a coprecipitation. The preconcentration of these trace elements was accomplished by converting the dissolved trace ions into the pyrrolidine dithiocarbonate (PDC) chelates, followed by coprecipitation on Bi as well as Pb-PDC chelates. This technique has been applied to the elements in natural waters: fresh water and sea waters (Mediterranian and Dead Sea).     

Progress on Detection of Metals Ions by Functional Nucleic Acids Biosensor

Functional nucleic acids are natural or artificial nucleic acid sequences with specific functions and special structures. A part of metal ions are essential trace elements of human health, but excessive metal ions will be harmful to human health. The functional nucleic acids are widely used for detection of metal ions because of its advantages such as easy modification, low price, high stability and strong specificity. This paper detailed the interaction between functional nucleic acids and metal ions, mainly including cutting type, link type, metal ion-mediated base pairing, click chemistry type, conformational change type, and other types. The biosensors based on the combination of functional nucleic acid with different signal output were then introduced. Finally, the research significance and existing problems of functional nucleic acid for metal ion detection were discussed. The future development trends and applications of functional nucleic acid biosensor were prospected.     

Study on chemical species of inorganic elements in some marine algae by neutron activation analysis combined with chemical and biochemical separation techniques

The compositional changes of inorganic elements on freshwater leaching of 35 species of Chinese algae were studied by the determination of the element contents in marine algae using instrumental neutron activation analysis. It was found that alkali metals and chlorine mainly exist as ions in algae, in which, water-soluble K and Na exist as chlorides. While, other elements exist as the states of both ions and organic combination in which the water leaching ratios of alkaline earth metals are the lowest. The combination of trace elements with various organic macromolecules inSargassum kjellmanianum was also studied using neutron activation analysis combined with chemical and biochemical separation techniques. The results indicate that the concentration of many trace elements, such as Zn, Fe, Sc, Th are earths in protein are quite high, and some trace elements can also be combined by pigment and polyphenol. Alkaline earth metal mainly bind with alginic acid inSargassum kjellmanianum.     

Preparation,properties and analytical application of silica with chemically grafted hydroxamic acid groups

The synthesis of silica chemically modified with propanohydroxamic acid groups and salicylhydroxamic acid is described. Sorption of 13 metal ions is studied as a function of pH. The composition of the sorbed complexes is determined and the apparent stability constants of the complexes in the sorbent phase are calculated. A correlation between the stabilities of the complexes in the sorbent phase and in aqueous solution is observed in some cases. Some analytical applications of the sorbents are demonstrated: trace amounts of elements can be concentrated from large volumes; molybdenum(VI) and zirconium(IV) can be separated from 10⁴-fold amounts of accompanying elements, and vanadium(V) can be determined in the sorbent phase by using diffuse reflection and photoacoustic spectrometric techniques.     

Preconcentration on hydrous magnesium oxide for neutron activation analysis

It was found that trace amount of various ions could be effectively adsorbed onto hydrous magnesium oxide from aqueous solution. Attempts were made to investigate the feasibility of using hydrous magnesium oxide as preconcentration agent for neutron activation analysis (NAA). The procedure was successfully applied for the measurements of trace amounts of elements in the surface water of a number of large rivers which play very important roles in the lives of local people. Some of them are polluted rather badly. In order to improve the living standards it is rather important to establish reliable analytical methods so that more effective surveillance may be enforced on pollution control problems. NAA is generally accepted as one of the most suitable methods for simultaneous and multielemental determination of trace amounts of elements. In this work polluted surface waters were investigated by NAA using Tsing Hua Open-pool Reactor (THOR).     

A novel solid-phase extraction method for separation and preconcentration of zirconium

This work assesses the use of modified natural clinoptilolite as an adsorptive material for separation and preconcentration of trace amounts of zirconium ions. A simple, rapid and economical method was developed for the preconcentration of trace amounts of zirconium in aqueous medium using 1-(2-pyridylazo)-2-naphthol as a complexing agent. Effect of sample pH, flow rate of sample and elution solutions, breakthrough volume and interference of several ions were studied. Determination of zirconium was made by ICP-AES technique. The sorption was quantitative in the pH range from 3.0 to 4.0, whereas quantitative desorption occurred instantaneously with 2 mol L^?1 hydrochloric acid. Linearity was maintained between 0.05 and 9.0 μg mL^?1. Relative standard deviations range from ±0.9% to ±2.3% (n?=?5). The detection limit was 0.1 ng mL^?1. Because of good recovery (>97%), this method is suitable for preconcentration and determination of zirconium in effluents containing trace amount of zirconium.     

Study of the application of atomic fluorescence spectrometry to the direct determination of mercury and cadmium in the atmosphere

Ion-exchange behaviours of Zr(IV), Nb(V), Ta(V) and Pa(V) on the anion exchanger Dowex 1-X8 are investigated first in a wide variety of aqueous mixed hydrochloric acid-hydrofluoric acid and secondly in the same aqueous system mixed with various organic solvents. Equilibrium adsorptions of these four elements as a function of hydrochloric acid concentration as well as hydrofluoric acid concentration, or both acid concentrations, were found to be strongly differentiated. This fact can be utilized for convenient separations of these elements from each other. Based on the equilibrium adsorption results, the possible complex formation of the metal ions and the separation possibilities for the elements are discussed.     

Preconcentration of trace amounts of silver ion in aqueous samples on octadecyl silica membrane disks modified with hexathia-18-crown-6 and its determination by atomic absorption spectrometry

A simple and reliable method has been developed to selectively separate and concentrate trace amounts of silver ion from aqueous samples for the subsequent measurement by atomic absorption spectrometry. Ag+ ions are absorbed quantitatively during passage of aqueous samples through an octadecyl-bonded silica membrane disk modified by hexathia-18-crown-6. Almost all matrix elements will pass through the disk to drain. The retained Ag+ ions are then stripped from the disk with a minimal amount of thiosulfate solution as eluent. The proposed method permitted large enrichment factors of about 200 and higher. The limit of detection of the proposed method is 50 ng Ag+ per 1,000 mL. The effects of various cationic interferences on the recovery of silver in binary mixtures were studied. The method was applied to the recovery of Ag+ ions from different synthetic and water samples.     

Radioactivation analysis of aluminium,vanadium, copper,molybdenum, zinc and uranium in natural water samples using organic coprecipitants

A method is described for the determination of trace metal ions, V, Al, Cu, Mo Zn, and U, in natural water samples by neutron activation analysis, using organic coprecipitation as a preconcentration method. The preconcentration of trace elements was accomplished by converting the dissolved trace metal ions into the oxine chelates atpH 5.2 and extraction of the chelates witho-phenylphenol which is a liquid above 56 °C and solidifies at room temperature. After cooling the extraction system, the fine particles of the organic phase were collected on a millipore filter and the precipitate was air-dried in a clean environment. The solid extract was wrapped up in a sheet of clean polyethylene and subjected to neutron irradiation in a reactor for less than 10 min at a thermal flux of 2·10¹³ n·cm⁻²·sec⁻¹. γ-Ray spectrometry by a coaxial Ge(Li) detector connected to a 1024-channel PHA was performed on the irradiated sample without further chemical separation, and thus the ppb level concentration of the elements in natural water samples could be determined. The fundamental study of the collection of the trace elements is also described.     

Über die Verwendung von Aktivkohle zur Anreicherung von Spurenelementen mit nachfolgender Bestimmung durch Atomabsorptions-Spektrometrie

Activated carbon can be used as collector material in trace analysis. Due to the special character of activated carbon, not only unsoluble compounds can be enriched, but also many soluble chelate complexes of trace elements. For that purpose the buffered aqueous solution of the analytical sample containing complexing or precipitating reagents is filtered through a small filter paper covered with 50 mg of activated carbon. The trace compounds, and in many cases also the surplus reagent are adsorbed by the collector. By treating the carbon collector with acid after the process of trace enrichment, a trace concentrate free of unwanted substances is obtained. Thus it is possible to use sensitive electrochemical and optical methods for the determination. For the determination of the enriched elements by atomic absorption spectrometry, the activated carbon suspended in diluted nitric acid can be dispersed directly into the atomizer. The carbon particles do not cause any interferences. The application and the advantages of activated carbon for enrichment of trace elements in high-purity materials is demonstrated by some analytical examples.     

Enrichment and determination of zinc by high-speed countercurrent chromatography.

The capability of high-speed countercurrent chromatography (HSCCC) has been investigated for enrichment and determination of metal ions at trace levels. Separation of selected divalent metal ions was performed using a small coiled column. A hexane solution of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPA) was employed as the stationary phase. Loaded divalent metal ions such as Ni, Co, Cu, and Zn were chromatographically eluted in the order of increasing extractability by passing a mobile phase buffered at a desired pH. Individual metal ions showed good linearity between concentrations and chromatographic peak areas of the absorbance, as detected by postcolumn reaction with 4-(2-pyridylazo)resorcinol (PAR). Metal ions enriched into the stationary phase from a sample solution were separated into individual metal ions. The trace quantity of zinc in natural mineral water was determined by enrichment separation through an HSCCC column.     

Photodegradation and by-products identification of commercial extractant Cyanex 302

The photodegradation of the organothiophosphorous extractant Cyanex 302 and purified bis(2,4,4-trimethylpentyl)monothiophosphinic acid dissolved in toluene was carried out in photoreactor using UV–Vis light irradiation. Possible degradation products were identified with the assistance of FT-IR, LC/MS/MS and GC/MS. The catalytic influence of zinc(II), copper(II) and cobalt(II) ions and the presence of trace values of water and aqueous solutions of sulphuric acids on the photodecomposition of Cyanex 302 were studied. The results demonstrated that the presence of trace amounts of water causes mainly the degradation of bis(2,4,4-trimethylpentyl)monothiophosphinic acid with the simultaneously fourfold increase in bis(2,4,4-trimethylpentyl)phosphinic acid concentration. The shaking with aqueous solution of sulphuric acids results in the decrease in the photodegradation probably by blocking of OH radical. Metal ions also affect the degradation causing the increase in bis(2,4,4-trimethylpentyl)phosphinic acid concentration. The photodegradation was also carried out in open atmosphere under sunlight and the obtained results were compared with those obtained in a Heraeus photoreactor.     

Chelating resin-impregnated paper chromatography, applications to trace element collection of ferrous and ferric ions, and determination by differential pulse anodic stripping voltammetry

An ion-exchange approach to the preparation of chelating resin is demonstrated whereby a typical sulfonated chelating agent, 7-iodo-8-hydroxy quinoline-5-sulfonic acid, is immobilized as counterions on a piperazinium polyelectrolyte matrix. The resulting chelate forming resin has been used to effect the selective separation of ferrous as well as ferric ion from a known mixture containing other trace elements without any complication of the leaching of either chelating ligand or resin from the stationary support. The chelating resin-impregnated paper chromatographic technique followed with differential pulse anodic stripping analysis is described for the preconcentration, separation, and recovery of divalent and trivalent ions of iron from the various heavy metals in aqueous phases. The combination of chelation and paper chromatography involves a differential migration procedure which provides a technique for the separation of analyte ions quantitatively without any interference from the complex matrices.     

8-Quinolinol-5-sulfonic acid-loaded resin as a preconcentrating agent in the neutron activation analysis of the chalcophile elements (author's transl)]

A chelating agent-loaded resin consisting of 8-quinolinol-5-sulfonic acid and an anion-exchange resin (HOx-resin) was prepared in order to concentrate trace chalcophile elements in natural water samples selectively before neutron activation analysis. The exchange capacity of the Diaion SA No. 100 for the reagent (1.8 meq . g-1 resin) corresponds approximately to that for chloride ion (1.83 meq . g-1 resin), indicating that 8-quinolinol-5-sulfonic acid is adsorbed quantitatively on the exchange site of the resin through the sulfonate anion in the reagent. The basic conditions for the adsorption of the metal ions on the resin were investigated by employing the column method. The nitrate concentration and the pH of the sample solution affect the adsorption behavior of metal ions. Several solutions containing metal ions with varying pH or varying nitrate concentration were applied to the resin column (35 mm x 7 mm phi) with a flow rate of 2.0 cm3 . min-1. As a result, the optimum conditions for the quantitative adsorption of copper(II), zinc(II), cadmium(II), cobalt(II), nickel(II) and manganese(II) were as follows: NO3- less than 0.01 mol . dm-3 pH greater than 4.6. Furthermore, the feasibility of the above conditions as well as quantitative adsorption of the chalcophile elements was confirmed through the neutron activation analysis of the synthesized metal solutions.     

Trace metal speciation by adsorptive stripping voltammetry of metal chelates of solochrome violet RS

Adsorptive stripping voltammetry has become one of the most sensitive methods for trace metal determinations. The growing application of the method to natural water systems prompted an investigation into the fraction of the metal concentration that contributes to the adsorptive stripping response. Recent procedures for trace measurement of iron, titanium and gallium, based on chelation with solochrome violet RS (SVRS) are coupled to systematic ligand competition experiments. Tannic acid, EDTA, NTA, glycine, cysteine, carbonate and chloride ions are used as model natural ligands. It is shown that adsorptive stripping voltammetry measures the free ion and metal displaced from complexes by the “analytical” ligand. The exact fraction of the metal measured thus depends on the thermodynamic stability of the metal-SVRS chelate (compared to that of natural complexes), and on the relative concentrations of the competing ligands. The method offers possible distinction between metal complexes, based on their thermodynamic stabilities. The use ofa large excess of the “analytical” ligand can lead to measurement of the total metal content. Implications of these results relative to the use of this procedure for studying the speciation of trace elements in natural waters are discussed.     

Preconcentration of Rare Earth Elements with 8-Hydroxyquinoline-5-sulfonic Acid Chelated Cellulose Filter Prior to Determination by Inductively Coupled Plasma Atomic Emission Spectrometry

ICP- AEShasbecome a widely used technique formulti- elemental major,minorand traceanalyses.However,many elements such as REEsare often presentin real samples atconcen-trations too low to be accurately determined by conventional ICP,especially in biological andenvironmental samples.Moreover the spectral interferences from matrix elementsoften inter-fere with trace REEsdetermination.To determine trace and ultra- trace REEsin complex ma-trices,the separation of the matrix components and th…     

Solvation of thiocyanate complexes of mercury(II) by 2-hexylpyridine from aqueous mineral acid solutions

The extraction of trace amounts of mercury(II) by 2-hexylpyridine dissolved in benzene from aqueous mineral acid solutions has been studied. The replacement of chloride, nitrate and sulfate ions by the potentially ambidentate, linear and less basic thiocyanate group offers interestingly high extraction coefficients. The value of the distribution coefficients may be lowered by complexing mercury with oxalate, thiosulfate, acetate or citrate ions in the aqueous phase. The possible mechanism of extraction has been discussed in the light of the results of extraction isotherms and slope analysis data. Distribution coefficients and separation factors of several metal ions relative to mercury(II) are reported for the three mineral acid systems and the possible removal of mercury along with some other inorganic pollutants from aqueous solutions is suggested.