Extraction Of Ag Research Articles

Electrochemical enzyme-immunoassay

Immunoassay defines the body of techniques which use the antibody (Ab) macromolecule, usually of the IgG class, for the detection and quantitation of an enormous range of simple and complex antigen (Ag) molecules. The success of the methods relies on both the specificity and formation constant of the Ab used, and the ability to detect the interaction between Ab and Ag. Sensitive assays in complex matrices require some kind of label to be present to provide this ability. The development of immunoassay methods has in large part been driven by the available technology. Thus, although one of the first immunoassays using a label was electrochemically based [1], the state of that art in 1951 was relatively primitive, and could not meet the analytical demands of the Ag. Some years later, Yalow and Berson [2] developed immunoassays based on the radioisotopic label (RIA). For the first time, Ab selectivity was married to very low detection limit technology, and the result was an enormous growth rate in the use of RIA in both the clinical and research laboratory. RIA has the significant advantage that the label used is not a normal constituent of physiological samples, and interferences of this type are therefore absent. RIA, however, has the disadvantages that accompany radioisotope handling, together with an inability to distinguish label which is bound from that which is not. There has therefore been an enormous effort to find suitable replacements for the radiolabel. Where the low detection limit of RIA was not required for a successful assay, labels detectable by spectroscopic methods have become important. Where very low detection limits are demanded, then the concept of amplification of, or by, the label has been developed. The most successful of these have been enzyme linked using an immunosorbent phase for Ag extraction (ELISA), although assays based on the lysis of label-containing liposomes are also exhibiting very low detection limits. In our hands, electrochemically based immunoassays at very low detection limits have also used enzyme amplification and ELISA, with either NAD/NADH and glucose-6-phosphate dehydrogenase [3], or phenyl phosphate/phenol and alkaline phosphatase [4]. The greatest sensitivity thus far has been obtained with ELISA coupled with liquid chromatography with electrochemical detection (LCED) [5]. The power of this approach can be readily illustrated by examining the evolution of its use in an assay for IgG, itself an important analyte. This evolution covers three principal stages of development and a reduction in detection limit of five orders of magnitude. The basic methodology is shown in figure 1. The assay is essentially a sandwich ELISA, using an alkaline phosphatase labelled second Ab for amplification. Oxidative flow amperometry at +875 mV

D2EHPAによる種々の金属イオンの溶媒抽出におよぼす非水溶媒の影響

Extraction of metal ions from the aqueous phase containing non-aqueous solvents such as dimethyl formamide (DMF), dimethyl sulfoxide (DMSO) and acetonitrile (AN) was investigated by using di-2-ethylhexylphosphoric acid (D2EHPA) as an extractant. The organic phase was a binary solution of D2EHPA and n-hexane, or D2EHPA and toluene, while the aqueous phase was a three-component solution of metal salt, non-aqueous solvent and water. Metal ions used for this purpose were Cr(III), Fe(III), Al, Cu, Ni, Co, Mg and Ag.The extraction of metal ions is strongly affected by the addition of non-aqueous solvent. The effect is dependent on the kinds of non-aqueous solvent, the amounts of non-aqueous solvent and the kinds of metal ion. The extraction behavior in the presence of non-aqueous solvents are classified into the following three groups: (1) extraction of Cu, Ni and Co increases by adding DMSO and DMF less than 50 vol% and then decreases by the addition more than 50 vol%, (2) extraction of Ag, Cr and Fe decreases with an increasing addition of DMSO and DMF, irrespective of its amount and (3) extraction of Mg and Al increases with an increasing addition of DMSO and DMF, regardless of its amount. The addition of AN does not cause a great change in the extraction of metal ions except Al and Ag, but the extraction of Ag is remarkably decreased by the addition of AN. The above extraction behavior may be explained by the complexing ability of non-aqueous solvents, the increase in the distribution amount of the extractant and extract in the aqueous phase, and the interaction between the extractant and non-aqueous solvents in the organic phase due to the dissolution of non-aqueous solvents in the organic phase.

LIQUID-LIQUID EXTRACTION STUDIES OF METAL IONS WITH DITHIACROWN COMPOUNDS

ABSTRACT The extraction properties of dibenzo-1, 10-dithia-[18]crown-6 compounds have been investigated. Especially thiophilic metals are effectively extracted. The extraction of Ag(I), Pd(II) and Au(III) is much greater than that of Hg(II) or Cu(I). Alkali and alkaline earth metals are not extracted. The experimental results show the coordination of metal ions with sulfur is decisive for the extraction. The variation of the subetituents at the macrocyclic ring from CH3- t o CH2Cl-groups influences the extraction power considerably. In contrast, the substitution on the benzo groups shows a less strong effect. The influence of diluents and counter anions on extraction are comparable with results in known crown ether systems. Synergistic extraction is observed for silver and mixtures of dithiacrown compounds and HDEHP, n-caprylic acid or TBP.

Solvent extraction of metals with macrocyclic compounds. II

Radioactive nuclides were used to study the extraction of Ag(I), Hg(II), Cd, Zn, Fe(III), Co(II), Cu(II), and Pb with solutions of 8.9; 18,19-dibenzo-1,7-dioxa-11,16-diazacyclononadeca-10,16-diene (I) and 8.9∶18,19-dibenzo-1,3,7-trioxa-11,16-diazacyclononadeca-10,16-diene (II). It has been established that of all the examined metals reagents I and II selectively extract only Ag(I). The composition of the extracted compounds has been established: silver is extracted in the form of AgLX compounds, where L is macrocycle I or II and X is the counterion. The counterions used were perchlorate, picrate (Pi), and, in the case of macrocycle II, also dipicrylaminate (DPA). The extraction is intensified, as the counterion increases in size and becomes more hydrophobic, in the series: ClO4 chloroform>xylene. Appropriate conditions have been created for quantitative extraction of silver with a solution of macrocycle I in dichloroethane. It is shown that large amounts of the 19 elements usually accompanying silver do not affect the degree of its extraction. The possibility of the extraction atomic-absorption determining silver with macrocycle I is indicated.

Mercury Removal From Gold Cyanide Leach Solution

The Bureau of Mines investigated selective extraction of Au and Ag from a low-grade Au ore containing Hg. Gold and silver were extracted from the ore in cyanide slurries, and Hg extraction was suppressed with sodium or calcium sulfide. Maximum Au extraction and minimum Hg extraction were obtained using solutions containing 17 kg NaCN/t of solution (0.34 lb NaCN/st). Increasing the cyanide concentration increased Hg extraction without increasing Au extraction. Mercury extraction from the ore was suppressed with 0.5–2.9 kg CaS/kg Hg (0.5–2.9 lb/lb) in the ore. Gold-to-mercury ratios of 100:1 to 400:1 were obtained in the leach solution, and on the activated carbon in a CIP circuit.

Solvent Extraction of the Nitrate Salts of K+, Ag+TI+and Pb2+Using Di(2-Ethylhexyl) phosphoric Acid and Dicyclohexano-18-Crown-6 in Toluene

Abstract A solvent extraction system is used to determine metal distribution coefficient, D n+, values between water and toluene for the nitrate salts of K+M, Ag+, T1+, and Pb2+ using, both individually and together, the organic soluble complexing agents HDEHP and DC18C6 (Figure 1). Synergistic solvent extraction effects.are found for all of the metals examined. The extraction of Pb2+ is much greater than that of the monovalent cations. The extraction of K+ increases either as the equilibration temperature decreases or as the equilibrated aqueous pH increases. The extraction of Ag+ increases in a regular fashion until the initial concentration of DC18C6 in the toluene reaches the initial concentration of HDEHP+in the toluene. Beyond this point, no appreciable increase in Ag+ extraction is observed with increased initial DC18C6 concentration.

Extraction of Ag(I), Cd(II), In(III), Sn(II), Sn(IV), Sb(III), and U(VI) from aqueous solutions by ketone solutions using single-step batch and continuous SISAK methods1,2

The extraction properties of Ag(I), Cd(II), In(III), Sn(II), Sn(IV), Sb(III), and U(VI) from aqueous KI/H2SO4 solution into a mixture of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK) and cyclohexanone (CHO) were studied. Both single-step batch and SISAK2 methods were used. The oxidation of Sn(II) to Sn(IV) by iodine and complexation of Sn(IV) by 2,3-dimercapto-propanol-1 (BAL) were also investigated. A method for rapid and continuous separation of indium from tin was developed for investigation of short-lived indium fission products.

Amorphous X films (X = C, Si, OR Re) prepared by extracting Ag with I from AgX films

A new technique to make amorphous (a) materials is described and successfully applied to C, Si and Re. The basic scheme consists in depositing a random solid solution or an amorphous XAg mixture where X is totally inert to I. The Ag atoms are then removed by exposing the XAg film to I, leaving an amorphous X film with a density appreciably lower than bulk. The technique was tested on CAg films since the resulting a-C films could be compapared with a-C films deposited by conventional means. X-ray fluorescence and neutron activation analysis established that the Ag extraction by I in a-C films several thousand Å thick is extremely good, with Ag residues ranging from 10 −4 to 10 −2 of the original Ag content. The resistivity at 300 K of these a-C films was as high as 10 7 Ω cm, 5 orders of magnitude above that of evaporated or sputtered a-C films. It is likely that this effect is due to the removal of defect states such as dangling bonds either by surface reconstruction or by the trapped I similarly to a-C:H films. The most rewarding application of this technique was the preparation of essentially pure (except for a few at% I) a-Re films, since Re films sputtered at 77 K are crystalline. The properties of these a-Re films fall in three classes depending on the original Re content of the starting ReAg film. At 90 at% Re, the a-Re films are superconducting at ⋍ 6 K; the resistivity is about 2 × 10 −4 Ω cm at 300 K and has a small negative temperature coefficient [ α = (d ϱ/ ϱ)d T = −3 × 10 −4 K −1] typical of amorphous metals. For Re concentrations between 43.5 and 59 at% the density of the a-Re films is about half that of bulk. The resistivity of these films displays two different types of temperature dependence: at intermediate resistivities [ϱ(300 K) ⋍ 2 × 10 −2 Ω cm] α = −3 × 10 −3 K −1 while for high room temperature resistivities (10 −1 to 10 4 Ω cm) ϱ ∼- exp T −1 2 . In other words, above 60 at% Re the a-Re films displays an essentially metallic conductivity while below 60 at% Re they are characterized by a semiconducting conductivity.

Thermodynamic studies of cryptand 222 and cryptates in water and methanol

Enthalpies of solution in water and in methanol are reported for a number of cryptate electrolytes ([M+222]+X–) and in conjunction with data on X– yield values for the enthalpy of transfer, ΔH°t, of [M+222] ions from water to methanol. Enthalpies of complexing of cations with cryptand 222 have been determined in water and methanol; when combined with known values of ΔH°t(M+) and the presently determined value of ΔH°t(222), they yield, via a thermodynamic cycle, values of ΔH°t for the ions [M+222] where M+= Li+, Na+, K+, Rb+, Cs+ and Ag+. The two methods of obtaining the ΔH°t values are in good agreement with each other.Solubility measurements on the perchlorates of [Na+222] and [K+222] yield values of ΔG°t([M+222]) from water to methanol. These values are also obtained from a thermodynamic cycle involving known values of ΔG°t(M+), the free energies of complex formation in water and methanol and the presently determined value of ΔG°t(222). The direct values and the cycle values are again in good agreement.ΔH°t, ΔG°t and ΔS°t values for transfer of the complexed ions [M+222] vary considerably with the central cation M+(M+= Li+, Na+, K+, Rb+, Cs+ and Ag+) and it is clear that the surrounding cryptand does not isolate the central ion from the environment. Also, various single-ion assumptions that require the constancy of ΔG°t([M+222]) and ΔH°t([M+222]) with M+ are not valid for the water to methanol transfer.Partition coefficients for the hypothetical extraction process M+(aq)+222(aq)→[M+222](methanol) have been obtained and it is shown that by comparison with the simple partition M+(aq)→ M+(methanol), greatly enhanced cation selectivities are observed. The largest selectivity enhancement occurs with the ions Ag+ and Li+, where the complex extraction equilibrium favours the extraction of Ag+ by a factor of 4 × 109 over the simple partition.Ion-pair partition coefficients have also been obtained for the species [Na+222]ClO–4 and [K+222]ClO–4; extraction of the latter is favoured by a factor of 1.6 × 102. This may be compared to a factor of 2.7 × 102 in favour of the potassium salt when extracted as the pair of ions ([M+222]+ ClO–4) and to a factor of 0.61 for extraction as the uncomplexed K+ and Na+ cations.

Extraction of silver(I) in the system tetrabutyl S-dithiopyrophosphate (TBDTPP)—electrolyte

The extraction of Ag+ ions was studied in the systems tetra-n-butyl S-dithiopyrophosphate [(BuO)2P(S)(O)P(S)(BuO)2]—TBDTPP in CCl4/HNO3 and TBDTPP/LiNO3. The extraction coefficients were determined as a function of the electrolyte and TBDTPP concentration. Infrared absorption studies have been undertaken to obtain information on the changes in the organic phase during the extraction of Ag(I). Analysis of the spectra has shown a shift of the P=S stretching band in the direction of lower frequencies. This is indicative of bond weakening and a decrease in the double bond character of P=S, due to withdrawal of electron density by the metal ion, and constitutes evidence for the coordination of Ag+ by thiophosphoryl groups of TBDTPP.

The extraction of mercury(II), silver(I), cobalt(II) and cadmium(II) by dioctylarsinic acid in chloroform

Dioctylarsinic acid (HDOAA) in chloroform solution has been investigated as a reagent for the extraction of Hg(II), Ag(I), Co(II), and Cd(II). Silver, cobalt and cadmium are not extracted below pH 7. An extraction coefficient of 1.1, constant over the pH range 1–6.5, was observed for Hg(II). With HCl concentrations of 1–8 M the extractability of mercury decreased slowly, reaching E a 0 = 0.05 at 8 M HCl. Silver formed a silver dioctylarsinate precipitate which collected at the interface. The extraction coefficients for Hg(II), Co(II) and Cd(II) increased above pH 7 to values of 20 (pH 9.1), 30 (pH 8.0), and 23 (pH 10), respectively. Reagent- and pH-dependence studies indicated that Co(II) and Cd(II) are extracted as M(DOAA) 2 or M(DOAA)Cl through interaction of HDOAA with M(OH) 2 or M(OH) +. Mercury was extracted from solutions of pH 1–6.5 as HgCl 2 (HDOAA) 2.5.

Extractive concentration of platinum-group elements and their determination by atomic-absorption spectrophotometry

The extraction of Pt, Pd, Ir, Rh, Ru, Ag, Au, Co, Cu, Ni and Fe with n-octylaniline has been investigated. Noble metals are extracted 10(3)-10(4) times better than Cu, Ni, Co and Fe. A method of determination of Pt, Pd, Ir, Rh and Ru is proposed. They are first separated from Cu, Ni, Co and Fe by means of extraction (and then determined, in either the aqueous or organic phase, by atomic-absorption spectrophotometry. The atomic absorption of platinum metals (with the exception of Pd) is affected by other elements of the platinum group and by non-noble metals. La(NO(3))(3) and Nd(NO(3))(3) lower the limit of detection for Pt, Rh, Ir and Ru and inhibit the effect of Co, Cu, Ni, Fe, Bi, Zn, Na, etc. on their determination. Lanthanum and neodymium chlorides and sulphates produce a similar effect but only on the determination of Pt and Rh. The coefficient of variation of the determination, in both phases, is within 2-6.8%.

Selenazone: the selenium analogue of dithizone

The selenium analogue of dithizone has been synthesised by treating 3-nitro-1,5-diphenylformazan or 3-methylmercapto-1,5-diphenylformazan with ammonia and hydrogen selenide in oxygen-free ethanol. The new reagent “selenazone” exists as tautomeric forms analogous to the thiol and thione forms of dithizone and is readily oxidised to a diselenide, C 26H 22N 8Se 2, from which the parent selenazone is recoverable by reduction with alkaline dextrose, sulphurous acid or hypophosphorous acid. The spectra of selenazone and the diselenide in a variety of organic solvents are reported and compared with similar data for dithizone itself. Selenazone forms a range of brilliantly coloured metallic complexes which are soluble in organic solvents. It thus permits of the solvent extraction of the ions Ag +, Mn 2+, Fe 2 +, Co 2+, Ni 2+, Cu 2+, Zn 2+, Cd 2+, Hg 2+, Pb 2+, Tl + and Bi 3+ from aqueous solution, the percentage extraction being governed by the pH. The diselenide also forms extractable coloured complexes; it is more selective than selenazone or dithizone, for the behaviour appears to be limited to Ag +, Hg 2+, Ni 2+ and Pd 2+.

Solvent extraction study in the silver(I)-8-hydroxyquinoline system

The extraction of Ag(I) with 8-hydroxyquinoline into chloroform was studied in the low range of 8-hydroxyquinoline concentrations. The existence of AgOx and AgOx 2 − in the aqueous phase was proved and their stability constants were determined. It was shown that Ag(I) is extracted as AgOx·HOx. The equilibrium extraction constants were determined. The structure of these complexes is discussed as well as the existence of AgOx·HOx in the aqueous phase.

Synthesis and properties of C 24 cyclic hydrocarbons

In this study, a novel and simple modified magnetic nanocomposite was investigated for the analysis of trace amount of silver(I). For this purpose, the magnetically activated carbon/γ-Fe2O3 (AC/γ-Fe2O3) nanocomposite was successfully synthesized and modified with a symmetrical thiourea derivative, 4,4′-bis-(3-phenylthiourea)diphenyl methane (BPDM). The different experimental factors affecting the preconcentration and detection of the analyte ions were studied in detail. The effects of foreign ions on the extraction of Ag(I) ions were also investigated. Under the optimum conditions, a sensitive response to Ag(I) within a wide concentration range (0.01–28 μg L−1) was achieved. The limit of detection (LOD, 3 Sb/m) was 2.3 ng L−1. The maximum adsorption capacity of the novel magnetic adsorbent for Ag(I) was found to be 32.6 mg g−1. An enrichment factor (EF) of 125 was obtained by the ratio of the highest sample volume for analyte (125 mL) and the lowest final eluent volume (1 mL). The developed method was successfully applied to monitoring silver in water samples and the certified reference material. The procedure exhibited some advantages, such as simplicity, rapidity, high sensitivity, and low cost. In addition, the mechanism of silver extraction by modified nanocomposite was proposed.