Quantitative paper chromatography : The separation and gravimetric determination of copper

Up to 50 mg of copper can be separated from similar quantities of silver, gold, platinum, rhodium, mercury and bismuth by a chromatographic method which employs butanol saturated with both 2 N NH₄OH and dimethylglyoxime as solvent. The copper may be quantitatively determined by electro-deposition from nitric acid solutions of the filtrates obtained. Strips of paper-pulp, approximately 250 mm long, 25 mm wide and 6 mm thick, and capable of absorbing 2 ml of solution on a spot 25 mm in diameter, are utilised.     

The trace determination of some heavy metals in waters by flow-injection spectrophotometry and potentiometry

Three automated flow-injection systems are proposed for the determination of traces of manganese(II), lead and copper(II) in waters. The first system utilizes the catalytic effect of manganese(II) on the oxidation of N,N-diethylaniline by potassium periodate at pH 6.86–7.10 (30°C) and is used for spectrophotometric determination at 475 nm in the range 0.02–1.00 μg1^?1; the system involves reagent injection and stopped flow. The determination of lead in the range 0.7–100 μg1^?1 is based on spectrophotometric detection of the lead 4/(2-pyridylazo)resorcinol complex at 525 nm after on-line preconcentration of the sample (5–50 ml) on a minicolumn filled with Chelex-100 or Dowex 1-X8 resin. A potentiometric flow-injection system with a copper ion-selective electrode is applied for the determination of 0.5–1000 μg 1^?1 copper(II) after on-line preconcentration of 50–500 ml of sample on Chelex-100 resin. The procedures are tested on synthetic and real water samples, including sea water and waste-waters.     

Coulometric titration of +2 copper with electrogenerated +2 tin

Using a supporting electrolyte composed of 4 M sodium bromide-0.2 N hydrochloric acid- 0.2 M stannic chloride, and a platinum generator cathode, +2 copper can be titrated accurately to the +1 state with electrogenerated +2 tin. With potentiometric end-point detection, quantities of copper from about 1 to 35 mg in a volume of 90 ml are titratable with an error of ± 0.3%. The titration is applicable in the presence of most of the elements that are commonly associated with Copper.     

Application of Fast Grey RA to the spectrophotometric determination of copper in liver of Egyptian camels

The ortho-orthohydroxyazo dye 15690-Solochromate Fast Grey RA, CI mordant Black 19 (reddish navy-blue black) has been used as a reagent for the spectrophotometric determination of copper in liver of Egyptian camels. To determine copper digest, 1-g dry liver samples with 5 ml of each of 50% v/v sulfuric and concentrated nitric followed by 3 ml hydrogen peroxide, get rid of excess acid by repeated evaporation and washing, transfer quantitatively to 100 ml flask, make with water up to volume, to 1 ml add 2 ml 0.05 N nitric, 2 ml 0.2 M ascorbic acid, 3 ml 0.005% FG make up with water to 10 ml. Measure extinction at 555 mμ. Such a procedure gave satisfactory results as compared to the DEDTC procedure and a recovery of 98.8%.     

Vanadametry Estimation of Thiosulphate

1.(a) We have found that sodium thiosulphate is quantitatively oxidized to tetrathionate in five minutes at room temperature (28°) by excess sodium vanadate in a medium containing sulphuric acid at 0.06N to 0.1N concentration and a little copper sulphate as catalyst. (b) Quantitative emulation of sodium thiosulphate to tetrathionate has also been achieved by the action of excess sodium vanadate during five minutes at room temperature in a medium containing 2.0N—8.0N acetic acid and a little copper salt as catalyst. Further oxidation to sulphate does not occur, even if the mixture is heated to boiling. (c) The excess of unreacted vanadate in 1(a) and 1(b) can be titrated with a standard solution of ferrous ammonium sulphate using diphenylbenzidine as indicator, after adding the requisite quantity of syrupy phosphoric acid. 2. On the other hand, sodium thiosulphate is easily and quantitatively oxidized to sulphate at room temperature, when. acted upon by excess sodium vanadate in a medium containing hydrochloric acid at an overall concentration of 5-6N and 1.0 ml of iodine monochloride as catalyst. The time required for reaction is ten minutes. The unreacted vanadate can be estimated by titration with a standard solution of ferrous ammonium sulphate, using N-phenylanthranilic acid as indicator or with diphenylbenzidine as indicator after suitably diluting and adding phosphoric acid.     

Determination of traces of antimony and tin in copper by anodic stripping voltammetry

The determination of antimony and tin impurities in copper by anodic stripping voltammetry on a hanging mercury drop electrode is described. Antimony and tin were previously separated from copper by distillation with hydrobromic acid or a mixture of hydrobromic acid and hydrochloric acid. The method was applied to the analysis of various high-purity copper samples, commercially available, showing satisfactory sensitivity and precision. The determination limit was about 1.4· 10^-9M for antimony and 7·10^-10M for tin in solution, for pre-electrolysis times of respectively 15 and 25 min; this corresponds to 0.8 p.p.b. of antimony and 0.3 p.p.b. of tin for a 2-g sample and a final volume of 10 ml after separation.     

Synthesis of precursors of poly(acryl amides) by copper mediated living radical polymerization in DMSO

The paper describes the optimization of copper(I) mediated living radical polymerization of N-hydroxysuccinimide methacrylate to achieve AB block copoly(acryl amides) offering a route to polymers with potential biomedical applications. Polymerization of N-hydroxysuccinimide methacrylate was carried out using copper(I) bromide/N-(n-propyl)-2-pyridylmethanimine catalyst with ethyl-2-bromoisobutyrate as the initiator at three different temperatures (70, 50 and 30 °C). Polymerizations at both 70 and 50 °C gave relatively high conversion, 72% and 62% respectively after 4 h. Polymerization at 30 °C the best linear first-order kinetic plot. The polydispersity remained narrow (1.15) and there was a good agreement between experimental, determined by ¹H NMR, and theoretical M_n. Polymerization of N-hydroxysuccinimide methacrylate was investigated in more detail by following reactions in situ by ¹H NMR. The experimental values of M_n (NMR) were quite close to the theoretical values and the polydispersities were relatively narrow (1.10-1.19). Isolated poly(N-hydroxysuccinimide methacrylate) was used as a macroinitiator for the polymerization of MMA catalyzed by Cu(I)Br in conjunction with N-(n-propyl)-2-pyridylmethanamine ligand leading to block copolymers. A poly(methyl acryl amide) is synthesized indirectly from the reaction of benzyl amine with poly(N-hydroxysuccinimide methacrylate) for 5 h with in DMSO at 50 °C under nitrogen.     

Effect of HC1 Concentration on the Distribution Factors of Iron and Mercury in Foam Separation

Abstract

A recycling batch foam separation apparatus has been used for the measurement of the distribution factors, Γ/c, of the anionic metal chloro complexes of iron and mercury with the cationic surfactant, hexadecyltri-methylammonium bromide. As a function of HC1 concentration, optimum values in distribution factors occur at roughly 0.3N HC1 for Hg and roughly 8N HC1 for Fe. Separations are thus possible by control of HC1 concentration.     

Optical sensor for sodium based on ion-pair extraction and fluorescence

A reagent phase that responds to sodium ion is used in a sodium-selective fiber-optic sensor. The components of the reagent phase are the ammonium salt of 8-anilino-1- naphthalenesulfonic acid (ANS), copper(II)—polyethyleneimine, and a commercial sodium-selective ionophore [N,N′,N″-triheptyl-N,N′,N″-trimethyl-4,4′,4″-propylidyne- tris(3-oxabutyramide)] immobilized on silica. In the absence of sodium, the ANS binds to the copper(II) polyelectrolyte and fluorescence is quenched. When sodium (20– 200 mM) is added, it forms a cationic complex which forms ion-pairs with some of the ANS, causing it to fluoresce. Response is linear at the lower sodium concentrations but tends to curve toward the concentration axis at higher concentrations. The sensitivity and the range of linear response depend on ANS concentration. Typically, it takes 1–3 min to reach 90% of steady-state response. The response time increases with decreasing temperature, increasing amounts of immobilized ionophore, and higher sodium concentrations. The selectivity of the sensor is established by the selectivity of the ionophore.     

Separation of alkaline earth elements by cation-exchange chromatography in ammonium malonate media

Be(II), Mg(II), Ca(II), Sr(II) and Ba(II) can be separated by elution from a cation-exchange column in the ammonium form with increasing concentrations of ammonium malonate. A typical elution sequence for a 60-ml column (volume in H⁺-form) of AG₅₀-X8 resin is: 200 ml of 0.20 N ammonium malonate plus 0.10 N malonic acid for Be(II); 300 ml of 0.50 N, 450 ml of 0.70 N, 350 ml of 1.10 N ammonium malonate for Mg(II), Ca(II) and Sr(II), respectively, and 200 ml of 3.0 N nitric acid for Ba(II). Separations are sharp and quantitative for element pairs in weight ratios from 1:1000 to 1000:1. Distribution coefficients, elution curves and quantitative separations are presented.     

Synthesis,Characterization and Solvatochromism Investigation of Mixed Ligand Chelate Copper(II) Complexes with Acetyleacetonate and Three Diamine Ligands

The syntheses of three mixed ligand chelate copper(II) complexes of the type [Cu(L)(acac)(H₂O)]BPh₄ where acac=acetyleacetonate; L=N,N‐dimethyl,N′‐benzylethane‐1,2‐diamine ( L¹ ), N,N‐dimethyl, N′‐2‐methylbenzylethane‐1,2‐diamine ( L² ) or N,N‐dimethyl,N′‐2‐chlorobenzylethane‐1,2‐diamine ( L³ ) are reported and characterized by elemental analyses, spectroscopic and molar conductance measurements. The X‐ray structure of complex 1 shows that the central copper atom is placed in a distorted square pyramidal geometry made by acac and diamine chelate in the base and a H₂O molecule on the apex. The prepared complexes are fairly soluble in a large number of organic solvents and show positive solvatochromism. Calculations of SMLR (stepwise multiple linear regression) method was utilized to find the best model explaining the observed solvatochromic behavior and showed that among different solvent parameters, donor number (DN) is a dominant factor responsible for the shift in the d‐d absorption band of the complexes to the lower wavenumber with increasing its values. The importance of substituent effect in diamine ligand on the spectral and SMLR measurements is also discussed.     

Preconcentration of copper with the ion-pair of 1,10- phenanthroline and tetraphenylborate on naphthalene

A solid ion-pair material produced from 1,10-phenanthroline and tetraphenylborate on naphthalene provides a simple, rapid and fairly selective means of preconcentrating copper from up to 1000 ml of aqueous samples (about 200-fold concentration is possible). Copper is quantitatively adsorbed in the pH range 1.6–10.4 at a flow rate of 3 ml min^?1. The solid mass (0.2 g) is dissolved from the column with 5 ml of dimethylformamide (DMF) and copper is measured by atomic absorption spectrometry at 324.7 nm. Linear calibration is obtained for 2–28 μg of copper in 5 ml of DMF solution. Replicate determination of 14 μg of copper gave a mean absorbance of 0.220 (n = 7) with a relative standard deviation of 1.5%. The sensitivity for 1% absorption was 0.093 μg ml^?1. After optimization, the method was applied to determine trace copper in standard reference materials, natural waters, beverages and hair.     

Dosierung kleiner Stickstoffdioxid-Mengen und Bestimmung des „Saltzman-Faktors“

A dynamic flow system is described by which N₂O₄ is diluted with air in 2 steps, to yield NO₂ concentrations in the partsper-million range. Part of the system is thermostatized. The final NO₂ concentration of the mixture can be calculated by taking into account the temperature and partial pressure dependent dissociation of N₂O₄. This system is used to test the Saltzman method, a photometric assay for the determination of NO₂, based on the formation of an intensely coloured azodye. The results obtained with gaseous NO₂ on one hand and with the equivalent amounts of aqueous nitrite solution on the other are compared. At a concentration of 1.5 μg NO₂ per 25 ml absorbing solution, the dye formation by 1 Mole of NO₂ equals that of 1 Mole of nitrite (“Saltzman-factor” 1.0). If the concentration is 10 μg/25 ml, the intensity of the colour effect due to 1 Mole of NO₂ equals 0.86 Moles of nitrite (“Saltzman-factor” 0.86). Only half the expected colour intensity was found when a NO₂-air-mixture was used that had been prepared by a dynamic two-step dilution and oxidation of NO (“Saltzman-factor” 0.5).     

The determination of copper in sea water by atomic absorption spectrometry with a graphite atomizer after elution from chitosan

Copper in sea water was determined by passing 1 1 of persulphate-pretreated sea water through a 30×3 mm chitosan column, and eluting with 20 ml of a 1% solution of 1,10-phenanthroline, or with 20 ml of 1 M sulphuric acid. Copper was determined in the eluates by hot graphite atomic absorption spectrometry. The result for Adriatic sea water (Ancona, Italy) was 6.06±0.56 μg Cu 1^?1. Diethylaminoethylcellulose, p-aminobenzylcellulose and Dowex A-1OO were also tested; Dowex A-100 collects only a minor part of the copper present in sea water.     

Energetics of the binding of Cu(II) ions by thermosensitive copolymers of N-vinylcaprolactam and N-vinylimidazole in different conformational states of macromolecules

Random and protein-like copolymers based on N-vinylcaprolactam and N-vinylimidazole are synthesized by free radical polymerization in an aqueous solution. The above copolymers show a different thermal behavior in aqueous media at pH 7.2. At 45°C, the solution of a random copolymer experiences phase separation, whereas a protein-like copolymer undergoes a transition from the unfolded conformation to the compact conformation without any phase separation. The method of isothermal titration calorimetry is used to study the binding of Cu(II) ions by protein-like and random copolymers of N-vinylcaprolactam and N-vinylimidazole at 25 and 45°C, which correspond to different conformational states of macromolecules. The standard enthalpy and constant of binding are estimated. For both copolymers, the enthalpies of binding are negative and similar. When temperature is increased from 25 to 45°C, the constant of binding of copper ions by a protein-like copolymer increases by more than three orders of magnitude, whereas the corresponding constant of a random copolymer remains almost unchanged. Therefore, the transition of protein-like copolymer from the coiled conformation to the compact conformation noticeably facilitates the formation of an imidazole quasi-receptor, which is characterized by a certain spatial configuration and by a high affinity for the functional ligand. This effect is provided by an entropy gain no less than 50 J/(mol K).     

Separation of chelating agents as copper complexes by capillary zone electrophoresis using quaternary ammonium bromides as additives in N-methylformamide

This study presents the use of quaternary ammonium bromides as additives in N-methylformamide (NMF) for the separation and quantification of chelating agents as copper complexes by capillary zone electrophoresis (CZE). The new quaternary ammonium bromides were synthesized in our laboratory and used for the first time for CZE applications performed in NMF media. The methods were developed and optimized for determination of six chelating agents (trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CDTA), diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA), nitrilotriacetic acid (NTA) and triethylenetetraaminehexaacetic acid (TTHA)) as copper complexes. Among the tested electrolyte additives in NMF media (pH_app 10.2) dimethyldioctylammonium bromide (DMDOAB), dimethyldinonylammonium bromide (DMDNAB) and dimethyldidecylammonium bromide (DMDDAB), at a concentration of 20 mmol L⁻¹ improved the separation of the copper complexes. The optimized methods require only 12 min for one analysis, and the detection limits for copper complexes of DMDNAB, the best-performing additive, were ≤24 μmol L⁻¹. Relative standard deviations (R.S.D.) for migration times were ≤2.5, ≤2.1, ≤3.1% and for peak areas, ≤3.1, ≤3.0, ≤3.2% for DMDOAB, DMDNAB and DMDDAB used as additives, respectively. All three methods were successfully applied to the analysis of natural and wastewater samples. No matrix effects from these samples were observed. The interaction between quaternary ammonium bromides and copper complexes is discussed.     

In vitro and in vivo studies of N,N′-bis[2(2-pyridyl)-methyl]pyridine-2,6-dicarboxamide–copper(II) and rheumatoid arthritis

The thermodynamic equilibria of copper(II), zinc(II) and calcium(II) with N,N′-bis[2(2-pyridyl)-methyl]pyridine-2,6-dicarboxamide (L1) have been studied at 25 °C and an ionic strength of 0.15 mol dm⁻³. Spectroscopic studies suggest metal ion complexation promotes deprotonation and coordination of the amide nitrogens resulting in overall tetragonal coordination of Cu²⁺. Blood–plasma modelling predicts that Cu(II) competes effectively against Zn(II) and Ca(II) for L1 in vivo. Octanol–water partition coefficient studies show that Cu(II)–L1 complexes are reasonably lipophilic. However, the CuL1H₋₂ species which predominates at the physiological pH of 7.4 has poor superoxide dismutase activity. Bio-distribution experiments showed activity accumulation and retention in the body of about 50% of the injected dose for the [⁶⁴Cu]Cu(II)–L1 complex after 24 h.     

Theoretical study of the stability of X N n (n=−1, 0, +1, +2; X=Ag,Cu;N≤25) clusters as a function of size using a non-local density functional formalism

The spherical jellium model and self-consistent Weighted Density Approximation (WDA) to density functional theory have been used to study the stability of X _N ⁿ (n=?1, 0, +1, +2; X=Ag, Cu;N≤25) clusters. The calculated magic numbers coincide with the observed ones. The first (IP1) and second (IP2) ionization potentials of Ag _N and Cu _N as a function of size show the typical oscillations induced by the electronic shell-filling effect. IP1 of Cu _N is about 0.5 eV higher than IP1 of Ag _N in the range studied (N≤25). For both Cu _N and Ag _N , IP1 appears to converge well towards the respective experimental values of the work function. The use of WDA allows us to obtain bound negative clusters of small size or with a nearly empty external shell, which is not possible using the Local Density Approximation (LDA) [1, 2]. However the electron affinity of X _N clusters obtained as the difference of energies of the neutral and the negatively charged clusters, becomes negative forN=2, 3 and 8 (very close to zero forN=8), revealing that WDA needs further refinements.     

The titrimetric determination of beryllium(II) with 1,2-phenylenediamine-N,N,N′,N′-tetraacetic acid

Beryllium (ca. 10^?2?10^?4 M) is determined by adding excess of 1,2-phenylenediamine-N,N,N′, N′-tetraacetic acid (PhDTA, H₄L) and back-titrating with copper(II); arsenazo-I serves as indicator. Formation constants of BeL and BeHL were determined by potentiometry: log K_BeL=6.48±0.02 and log K^H_BeHL=3.48±0.03 (25°C, I=1 M in NaClO₄). Expressions for the titration curve are given together with theoretical errors.     

Photofunctional supramolecular solution systems of chiral Schiff base nickel(II), copper(II), and zinc(II) complexes and photochromic azobenzenes

Preparations, crystal structures, electronic and CD spectra are reported for new chiral Schiff base complexes, bis(N-R-1-naphthylethyl-3,5-dichlorosalicydenaminato)nickel(II), copper(II), and zinc(II). Nickel(II) and copper(II) complexes adopt a square planar trans-[MN₂O₂] coordination geometry with Δ(R,R) configuration. While zinc(II) complex adopts a compressed tetrahedral trans-[MN₂O₂] one with Δ(R,R) configuration and exhibits an emission band around 21 000 cm⁻¹ (λ_ex = 27 000 cm⁻¹). Absorption and CD spectra were recorded in N,N′-dimethylformamide, acetone, methanol, chloroform, and toluene solutions to discuss relationships between spectral shifts of d–d and π–π^∗ bands by structural changes of the complexes and physical properties of the solvents. Moreover, we have attempted to investigate conformational changes of the complexes induced by photoisomerization of azobenzene, 4-hydroxyazobenzene, or 4-aminoazobenzene, in various solutions under different conditions. Weak intermolecular interactions between complexes and azobenzenes are important for the phenomenon by conformational changes of bulky π-conjugated moieties of the ligands.