Flotation-spectrophotometric determination of osmium (ruthenium) with thiocyanate and Capri blue

A sensitive flotation-spectrophotometric method for the determination of osmium, based on the ion associate formed by the anionic thiocyanate osmium complex with oxazine basic dye, Capri blue (CB), has been developed. The ion associate is separated by shaking the aqueous solution (pH 2–3) with diisopropyl ether, washing the precipitate with water, and dissolving it in methanol. Molar absorptivity in this method amounts to 2.7 × 10⁵ liters mol⁻¹ cm⁻¹ at 630 nm. The molar ratio Os:SCN:CB in the separated associate is 1:8:5. Under the conditions of the determination of osmium, ruthenium can be determined as well. Metals that form anionic thiocyanate complexes, including other platinum metals, interfere. The method becomes highly selective for osmium and ruthenium after their separation by distillation as tetroxides. Osmium and ruthenium were determined with Capri blue after their extractive separation as thiocyanate complexes.     

Extraction chromatography of chloride complexes of osmium (III, IV and VI) on paper treated with tributyl phosphate and amberlite LA-1 hydrochloride

The complex anions OsCl₆²⁻, OsO₂Cl₄²⁻ and OsCl₆³⁻ were separated by extraction chromatography on paper treated with tributyl phosphate and developed with hydrochloric acid. The chloride complexes of osmium and ruthenium can also be separated in the system TBP-HCl or Amberlite LA-1 hydrochloride-HCl.     

Voltammetry and electrochemical stripping analysis for antimony in aqueous and nonaqueous media after extraction

Cyclic voltammetry of antimony was studied in aqueous media (HCl-LiCl) and in nonaqueous media after extraction with 20% tri-n-butylphosphate in toluene, with a rotating glassy carbon disc electrode. Reduction of antimony to the element in aqueous media is nearly reversible, but irreversible in nonaqueous media. Anodic stripping voltammetric and chronopotentiometric determinations were also studied in nonaqueous media; methanol and LiCI, NH₄SCN or NH₄NO₃, were used as base electrolytes. In nonaqueous media, antimony can be determined down to concentrations of 1O⁻⁸ M by stripping voltammetry, and lO⁻⁷ M by stripping chronopotentiometry. Electrochemical stripping determinations of 10⁻⁶ M antimony(III) were not affected by Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺ or As³⁺ (5 · 10⁻³ M), ag⁺ (4 · 10⁺⁴ M in stripping voltammetry or 10⁻³ M in stripping chronopotentiometry), Hg²⁺ (5 · 10⁻⁴M), Pb²⁺ (3 · 10⁻⁴ M), Cu²⁺ (1.5 · 10⁻⁴ M)Sn²⁺ and Sn⁴⁺ (7 · 10⁻⁴ M), Fe³⁺ (4 · 10⁻⁴ M), Au³⁺ (5 · 10⁻⁵ M) and Bi³⁺ (1.5 · 10⁻⁵ M). Thestripping chronopotentiometric determination showed better selectivity.     

Electrochemical and DNA-binding properties of dipyridophenazine complexes of osmium(II)

A transition metal complex as an electrochemical probe of a DNA sensor must have an applicable redox potential, high binding affinity and chemical stability. Some complexes with the dipyrido[3,2-a:2′,3′-c]phenazine (DPPZ) ligand have been reported to have high binding affinity for DNA. However, it was difficult to detect the targeted DNA electrochemically using these complexes because of the relatively high redox potential. In this work, a combination of bipyridine ligands with functional groups (---NH₂, ---CH₃ and ---COOH) and the DPPZ ligand were studied. The introduction of electron-donating groups was effective for controlling the redox potential of the DPPZ-type osmium complex. The [Os(DA-bpy)₂DPPZ]²⁺ complex (DA-bpy; 4,4′-diamino-2,2′-bipyridine) had a lower half-wave potential (E_1/2) of 147 mV (vs. Ag AgCl) and higher binding affinity with DNA {binding constant, K=3.1×10⁷ M⁻¹ in 10 mmol dm⁻³ Tris–HCl buffer with 50 mmol dm⁻³ NaCl (pH 7.76)} than those of other complexes. With the single stranded DNA (ssDNA) modified gold electrode, the hybridization signal (ΔI) of the [Os(DA-bpy)₂DPPZ]²⁺ complex was linear in the concentration range of 1.0 pg ml⁻¹–0.12 μg ml⁻¹ for the targeted DNA with a regression coefficient of 0.999. The detection limit was 0.1 pg ml⁻¹.     

Spectrophotometric determination of osmium

Summary m-Amino benzoic acid in large excess reacts with tetra-, hexa- and octavalent osmium at theph range 4.5–6 to give a purple complex having absorption maximum at 500 nm. Beer's law is obeyed for 0.5 to 8 ppm of osmium(VI) and osmium(VIII) with optimum concentration range of 2 to 8 ppm of osmium(VI) and 3 to 8 ppm for osmium(VIII). The per cent relative error per 1% absolute photometric error is 2.8 for both osmium(VI) and osmium(VIII). Ions such as Pd²⁺, Rh³⁺, Ir⁴⁺, W⁶⁺, U⁶⁺, Co²⁺, Hg²⁺, Mg²⁺, Ca²⁺, Ba²⁺, Sr²⁺, Th⁴⁺ and Zr⁴⁺ do not interfere in the determination.Molar ratio method indicates that the reagent first reduces osmium (VIII) and osmium(VI) to osmium(IV), which then probably forms a 11 complex with the excess unoxidised reagent.Part III.: Anal. chim. Acta 22, 306 (1960); cf. Z. analyt. Chem. 177, 291 (1960).     

Copper(II)-cetyltrimethylammonium chloride-chromal blue G ternary complex and its application to the spectrophotometric determination of copper(II)

A sensitive spectrophotometric method for the determination of copper(II) based on a ternary complex with chromal blue G, a triphenylmethane reagent in the presence of cetyltrimethylammonium chloride, is described. The sensitivity of color reaction between copper and chromal blue G has been greatly increased by the sensitizing action of cetyltrimethylammonium chloride, a cationic surfactant. The color development of the ternary complex can be utilized in the highly sensitive spectrophotometric determination of copper. The molar absorptivity of the binary complex between copper and chromal blue G ε_630nm = 9.56 × 10³liters · mol⁻¹ · cm⁻¹ is enchanced on ternary complex formation to ε_{542 nm} = 4.78 × 10⁴liters · mol⁻¹ · cm⁻¹. The ternary complex gave a maximal absorbance at 542 nm in the pH range 9.8–11. Beer's law is obeyed up to at least 1.2 ppm of copper. The maximal absorbance of the ternary complex was found to develop within 5 min and then it remains constant for several hours. The formation constant of the ternary complex is calculated to be 8.6 × 10¹⁰ under these conditions.     

Preconcentration of metal ions using an immobilized dialkyldithiocarbamate in a flow system

Flow injection analysis with on-line preconcentration using a minicolumn loaded with dialkyldithiocarbamate immobilized on controlled pore glass is described for the determination of Rh(III), Co²⁺, Cu²⁺, Hg²⁺, and Hg₂²⁺. The detection limits range from 0.05 ng ml⁻¹ for Cu²⁺ to 50 ng ml⁻¹ for Hg²⁺ for 5- or 10-ml samples, improvement of 2–3 orders of magnitude compared with direct injection. The operating conditions are optimized and the effects of interferents are studied. The capacity of the collector varied from 0.9 mmol g⁻¹ for Rh(III) to ca 4 mmol g⁻¹ (Co²⁺, Cu²⁺, Hg²⁺).     

Some observations on the solvent extraction and spectrophotometric determination of palladium using 3,4-dihydro-4,4,6-trimethyl-2(1H)-pyrimidine-thione as a selective reagent

A highly selective spectrophotometric method is described for the determination of palladium, using 3,4-dihydro-4,4,6-trimethyl-2(1H)-pyridinethione (DTPT). The intense yellow 1:2 complex is extractable in chloroform from aqueous solution of pH 5.5. The maximum absorption occurs at 420 nm, ε = 3.90 × 10⁴ liter/mol⁻¹ cm⁻¹ and the sensitivity of the determination is 0.023 μg/ml. Palladium can be determined over a range of 0.4–24.6 ppm. CN⁻ interferes in this determination and should be absent. The method is applied to the determination of palladium in hydrogenation catalysts.     

Selective separation of gold from iron ore samples using ion exchange resin

Gold in iron ore samples is separated from iron (major matrix cation), antimony and vanadium using anion exchange resin in (0.2 M) HBr, potassium peroxodisulfate and acetone:water:nitric acid media. The exchangeable anion Cl⁻ of the ion exchanger Dowex 1X 4 is replaced by Br⁻ using (6 M) HBr solution. Certified reference material DGP-M1, spiked ferric magnetic oxide, gold radioactive tracer ¹⁹⁸Au and gold standard solutions are used to study the adsorption efficiency and the yield recovery of tetrabromoaurate AuBr₄⁻ from the resin. Ten eluents have been tried to elute gold from the column, and it has been found that a 10 ml potassium peroxodisulfate and 240 ml acetone:water:nitric acid [125:5:5] solution fulfills the objective. The set up of the separation procedure allows quantitative adsorption of gold by the resin, while the major matrix cation (Fe) and others (Cd, Ag, Cu, V, Sb, Ti) have been passed through the column with the feeding solution (0.2 M) HBr. The resin selectivity coefficient (K) of separating Au from Fe has been found to be K_Fe^Au≈6.4×10¹¹. The eluted Au is treated with K₂S₂O₈ and H₂O₂ for spectrophotometric determination as rhodamine-B complex at 555.6 nm. The linearity, detection limit, precision, and accuracy of the determination method have been found to be up to 2.0 μg g⁻¹, 0.018 μg g⁻¹, 0.009 μg g⁻¹ and 3%, respectively.     

Solid substrate-room temperature phosphorimetry for the determination of trace protein using ion association complex [Cu(BPY)2]·[(Fin)2] as a phosphorescent probe

Fluorescein (HFin) emitted strong and stable room temperature phosphorescence (RTP) on filter paper after set at 50 °C for 10 min using Li⁺ as the ion perturber. HFin existed as Fin⁻ when the pH value was in the range of 5.45–7.36. Fin⁻ could react with [Cu(BPY)₂]²⁺ (BPY: α,α-bipyridyl) to produce ion association complex [Cu(BPY)₂]²⁺·[(Fin)₂]²⁻, which could enhance the RTP signal of Hfin. In the presence of bovine serum albumin (BSA), the –COOH group of Fin⁻ in the [Cu(BPY)₂]²⁺·[(Fin)₂]²⁻ could react with the –NH₂ group of BSA to form the ion association complex [Cu(BPY)₂]²⁺·[(Fin-BSA)₂]²⁻, which contained –CO–NH– bond. This complex could sharply enhance the RTP signal of Hfin and the ΔI_p was directly proportional to the content of BSA. According to the facts above, a new solid substrate-room temperature phosphorimetry (SS-RTP) for the determination of trace protein had been established using the ion association complex [Cu(BPY)₂]²⁺·[(Fin)₂]²⁻as a phosphorescent probe. This method had wide linear range (0.40 × 10⁻⁹–280 × 10⁻⁹ mg l⁻¹), high sensitivity (the detection limit (LD) was 1.4 × 10⁻¹⁰ mg l⁻¹), good precision (RSD: 3.4–4.9%) and high selectivity (the allowed concentration of coexistent ions or coexistent materials was high). It had been applied to the determination of the content of protein in 10 kinds of real samples, and the result agreed well with pyrocatechol violet-Mo (VI) method (P.V.M.M.), which indicated it had high accuracy. Meanwhile, reaction mechanism for the determination of trace protein with [Cu(BPY)₂]²⁺·[(Fin)₂]²⁻ phosphorescent probe was also discussed. The academic thought of this research could not only be used to develop many kinds of ion association complex phosphorescent probes, but also provided a new way to promote the sensitivity of SS-RTP.     

Continuous Determination of Trace Amounts of Humic Acid in Natural Water by Chemiluminescence Method

A chemiluminescence (CL) method for the determination of humic acid (HA) based on the oxidation of HA with hydrogen peroxide in the presence of formaldehyde in alkaline solution is described. This method is sensitive and selective for the determination of HA in natural water. HA produces strong CL in the oxidation of HA with MnO₄⁻, Br₂, ClO⁻, and Cr₂O₇²⁻, and the H₂O₂. HA-H₂O₂-HCHO system is suitable for the determination of HA because of its high sensitivity and high selectivity. The detection limit was 50 ppb and relative standard deviation for five measurements of 0.5 ppm (w/w) HA was 1.8%. Cations such as Na⁺, K⁺, Mg²⁺, Cu²⁺, and Fe3⁺ and anions such as PO₄³⁻, NO₃⁻, CO₃²⁻, SO₄²⁻, Cl⁻, and Y⁻ (EDTA-Na) did not interfere with the determination of HA. Addition of Mn(II) increased the CL intensity. The concentration of HA in natural water determined with this method is in good agreement with that determined by fluorometric analysis.     

Synthesis and Structure of Heterometallic Bi(III) Complex with Diethylenetriaminepentaacetic Acid

A new heterometallic Bi(III) complex with diethylenetriaminepentaacetic acid anion (Dtpa)⁵⁻ of the composition [Co(Tsc)₃]₂[Bi(Dtpa)]₂SO⁴ ⋅ 6H₂O (I) (Tsc is thiosemicarbazide) is synthesized and its crystal structure is determined. The complex consists of the [Co(Tsc)₃]³⁺ cations, [Bi(Dtpa)]²⁻ and SO ₄ ²⁻ anions, and crystallization water molecules. The SO ₄ ²⁻ ion and two water molecules are randomly disordered over two positions. In the complex cation [Co(Tsc)₃]³⁺, the metal polyhedron has fac-form. The carboxyl groups of octadentate (Dtpa)⁵⁻ ligand in the [Bi(Dtpa)]²⁻ anion are fully deprotonated. The coordination polyhedron of the Bi atom is a distorted bicapped trigonal prism. Thermogravimetric analysis of complex I indicates that its decomposition occurs through several stages, i.e., dehydration, burning of organic ligands, and the formation of inorganic residue.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 6, 2005, pp. 446–454.Original Russian Text Copyright © 2005 by Bulimestru, Petrenko, Gulea, Gdaniec, Simonov.     

Kinetic Determination of Mercury(II) at Trace Level from Its Catalytic Effect on a Ligand Substitution Process

A catalytic kinetic method (CKM) is presented for the determination of mercury(II) based on its catalytic effect on the rate of substitution of N-methylpyrazinium ion (Mpz⁺) onto hexacyanoferrate(II). The progress of the reaction was monitored spectrophotometrically at 655 nm by registering the increase in absorbance of the product [Fe(CN)₅(Mpz]²⁻ under the reaction conditions: 5 × 10⁻³ mol L⁻¹ [Fe(CN)₆]⁴⁻), 5 × 10⁻⁵ mol L⁻¹ [Mpz⁺], T = 25.0 ± 0.1°C, pH 5.00 ± 0.02 and ionic strength, I = 0.1 mol L⁻¹ (KNO₃). Quantitative rate data at specified experimental conditions showed a linear dependence of the absorbance after fixed time A _t on the concentration of mercury(II) catalyst in the range 20.06–702.1 ng mL⁻¹. The maximum relative standard deviations and percentage errors for the determination of mercury(II) in the range of 20.06–200.6 ng mL⁻¹ were calculated to be 1.7 and 2.7% respectively. The detection limit was found to be 7.2 ng mL⁻¹ of mercury(II). Accuracy (expressed in terms of recoveries) was in the range of 98–103%. Figures of merit and interference due to many cations and anions was investigated and discussed. The applicability of the method was demonstrated by determining the mercury(II) in different synthetic samples and confirming the results using atomic absorption spectrophotometry. The proposed method allowed determination of mercury(II) in the range 20.06–702.1 ng mL⁻¹ with very good selectivity and an output of 30 samples h⁻¹.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 654–661.Original English Text Copyright © 2005 by Surendra Prasad.This article was submitted by the author in English.     

Absorptiometric determination of micro- and submicroamounts of iron using an extractive method with pyridine-2-acetaldehyde salicyloylhydrazone

The formation and extraction into chloroform of iron complex with PASH (λ_max = 640 nm) was studied. Beer's law is obeyed between 2.7 and 16.0 μg · ml⁻¹ of iron, in organic phase (10 ml). The method can be applied to volume ratios V_aq.:V_org. from 1:1 to 20:1. The minimum concentration determinable in aqueous phase is 135 ng ml⁻¹ of iron. The interferences of 73 species were evaluated and eliminated when it was possible. The extraction method of the green complex was applied for the spectrophotometric determination of iron(II) in several standard, geochemical, and bromatological samples. A procedure based on the standard addition method was applied satisfactorily to the determination of as little as 25 ng of iron(II) per milliliter.     

Reactions of sulfur(IV) with an octahedral manganese(IV) complex of 1,8-bis(2-hydroxy benzamido)-3,6-diaza octane: the role of phenolate–amide–amine coordination

The Mn^IV complex of tetra-deprotonated 1,8-bis(2-hydroxybenzamide)-3,6-diazaoctane (Mn^IVL) engrossed in phenolate-amido-amine coordination is reduced by HSO₃⁻ and SO₃²⁻ in the pH range 3.15–7.3 displaying biphasic kinetics, the Mn^IIIL⁻ being the reactive intermediate. The Mn^IIIL⁻ species has been characterized by u.v.–vis. spectra {λ _max, (ε, dm³ mol⁻¹ cm⁻¹): 285(15 570), 330 sh (7570), 469(6472), 520 sh (5665), pH=5.42}. SO₄²⁻ was the major oxidation product of S^IV; dithionate is also formed (18 ± 2% of [Mn^IV]_T) which suggests that dimerisation of SO₃^−• is competitive with its fast oxidation by Mn^IV/III. The rates and activation parameters for Mn^IVL + HSO₃⁻ (SO₃²⁻) → Mn^IIIL⁻; Mn^IIIL⁻ + HSO₃⁻ (SO₃²⁻) → Mn^IIL²⁻ are reported at 28.5–45.0 °C (I=0.3 mol dm⁻³, 10% (v/v) MeOH + H₂O). Reduction by SO₃²⁻ is ca. eight times faster than by HSO₃⁻ both for Mn^IVL and Mn^IIIL⁻. There was no evidence of HSO₃⁻/SO₃²⁻ coordination to the Mn centre indicating an outer sphere (ET) mechanism which is further supported by an isokinetic relationship. The self exchange rate constant (k₂₂) for the redox couple, Mn^IIIL⁻/Mn^IVL (1.5 × 10⁶ dm³ mol⁻¹ s⁻¹ at 25 °C) is reported.     

Spectrophotometric study of pseudopurpurin-Pd(II) dimer complex. Spectrophotometric determination of traces of Pd(II)

We have studied spectrophotometrically the Pseudopurpurin-Pd(II) complex in an ethanolic-water medium ¦Ethanolamine ¦_optimum = 4 × 10⁻¹M; λ = 670 nm; 20% H₂O; stable for at least 4 hr; ¦Reagent¦_optimum = 5 × 10⁻⁵M; stoichiometry 2:2; log K = 17.7. A new method for the spectrophotometric determination of Pd traces is proposed for concentrations between 0.30 and 2.40 ppm. The relative error and the interferences of the method have been investigated.     

A study of the spectrophotometric determination of traces of cadmium(II) and copper(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the presence of polyglycol octylphenyl ether

A spectrophotometric study of the Cd(II) and Cu(II) complex of a new reagent, 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol (5-Br-PADAP) in the presence of polyglycol octylphenyl ether (OP) is presented. A reddish binary complex is formed at pH 9 and shows maximal absorbance at 560 nm with molar absorptivity of 1.16 × 10⁵ · mol⁻¹ · cm⁻¹ liter (Cd), 1.5 × 10⁵ mol⁻¹ · cm⁻¹ · liter (Cu). Beer's law is followed over the range 0.0 to 20 μg cadmium(II) and 0.0–18 μg copper(II). The continuous variation method and molar ratio method showed that the metal ligand ratio is 1:2; ordinarily, most ions do not interfere with the determination and the method can be applied for direct spectrophotometric determination of cadmium(II) and copper(II) in actual samples and the results obtained are satisfactory.     

Spectrophotometric determination of titanium in plants using 5,5′-thiodisalicylic acid

Titanium (IV) forms a yellow-colored chelate with 5,5′-thiodisalicylic acid, whose sensibility is pD = 6.1 between pH 4 and 6. The stoichiometry of the complex formed is 1:1 at pH 0.5. The system follows Beer's law at pH 4.9 (λ = 385 nm) over the concentration range 0.6–3.2 ppm (ε = 16000 liters · mol⁻¹ · cm⁻¹). The method can be suitably used for determination of titanium in plants.     

A study on terbium sensitized chemiluminescence of ciprofloxacin and its application

A novel rapid flow injection method with chemiluminescence (CL) detection was established for the determination of ciprofloxacin (CPLX), which is an antibiotic commonly used. The method is based on CL of Ce(IV)–SO₃²⁻ sensitized by Tb³⁺–CPLX, and showed the intensive bands characteristic of Tb³⁺ (⁵D₄→⁷F₅). The optimum conditions for CL emission were investigated. The linear relationship between the relative CL intensity and the concentration of CPLX is in the range of 9.0×10⁻⁹–1.0×10⁻⁶ mol/l with a detection limit of 3.1×10⁻¹⁰ mol/l. The relative standard deviation is 2.8% (n=11) for a level of 5.0×10⁻⁸ mol/l. The method was applied to the analysis of CPLX in human serum and urine samples with satisfactory results. The possible mechanism for this sensitized CL reaction is also discussed.     

Spectrophotometric determination of osmium with phthalimide dithiosemicarbazone by means of complex formation and catalytic reactions

Phthalimide dithiosemicarbazone forms a 1:1 complex with osmium at pH 3.3–4.5 (?₄₅₀ = 1.3 · 10⁴ l mol^?1 cm^?1 ) which is applied to the photometric determination of osmium; Beer's law is obeyed for the range 1–12 μg Os ml^?1. The oxidation of the reagent with cerium(IV) is catalyzed by osmium(VIII), and this reaction allows a more sensitive procedure for the determination of osmium; the calibration curve is linear over the range 0.05–0.4 μg Os ml^?1. The interferences in both procedures are described.