Complex-forming Reagents Research Articles

Preventing scale formation on heat transfer surfaces

The article considers the problem of scaling in power equipment on the example of Thermal Power Plants in the Republic of Kazakhstan. The most optimal solution is proposed – replacement of the traditional preparation of the feed water in the heat network by an ion exchange method for a more effective method using complex-forming reagents. The influence of inhibitor of mineral salts concentration (IMSC), trisodium phosphate, and Zinc Complex 1-hydroxyethylendiphosphonic acid (Zn-OEDF), as well as the heat carrier temperature on scaling intensity, has been studied to prevent the equipment from scale formation and corrosion. The technological parameters of feed water in the presence and absence of complex formers have been determined. The corrosion resistance of steel No. 3 samples in the presence of said reagents has been studied. The most optimal complexone has been chosen to prepare feed water for the TPP heating network.

Extraction properties of 4-[(hexylsulfanyl)methyl]3,5-dimethyl-1-phenyl-1<i>H</i>-pyrazole in the palladium(II) recovery from nitric acid solutions

Palladium(II) extraction from nitric acid solutions with a complex-forming reagent, 4-[(hexylsulfanyl)methyl]-3,5-dimethyl-1-phenyl-1 H -pyrazole, was studied using chloroform as a diluent. The reagent extracts Pd(II) with high efficiency from 0.5-5 M. HNO3 solutions. It has been established that palladium(II) is extracted from 2 M. HNO3 solutions by a coordination mechanism with the formation of the extracted compound [Pd(NO3)2μ-L] n ( n > 2). Palladium(II) is quantitatively stripped with a nitric acid solution of thiourea. The reagent is promising for the concentration of Pd(II) from nitric acid solutions and its highly selective separation from Fe(III), lanthanides(III), Al(III), Cu(II), and Ni(II).

Recovery of noble metals from refractory sulfide black-shale ores

The processing of refractory sulfide black-shale ores and concentrates from the Sukhoy Log deposit containing gold, silver and platinum group metals (palladium and platinum) was investigated. The noble metals were leached both under atmospheric pressure and at 700kPa at 200°C in an autoclave. It was found that the preferred leaching method is the chlorination of the ore in HCl/NaCL solutions in the presence of MnO2. The sorption recovery of noble metals on Purolite anion exchangers and carbon adsorbent Calgon GRC-22 was carried out from solution with the following initial concentrations of noble metals (in mg/L): Au — 25; Pt — 5; Pd — 5; and Ag — 10 in the presence of 1M FeCl3, 0.1 М CuCl2, 1M NaCl and 1М HCl. It was shown that the chloride complexes of noble metals can be effectively adsorbed from this solution. Then, the selective elution of noble metals from anion exchangers Purolite A170 and Purolite S992 by means of different complex-forming reagents was studied. The best elution results were obtained with Na2SO3+NaNO2 and thiourea solutions.

Innovative technology for recycling the negative segments of alkaline batteries using recoverable solvent

Technology is presented for recycling the negative segments of nickel-cadmium batteries based on the use of sodium ethyelenediaminetetraacetate (EDTA) as a leaching (complex-forming) reagent. Methods are proposed for recovering the solvent and cadmium oxide preparation, suitable for manufacturing alkaline storage batteries. The technology developed is distinguished by a high degree of cadmium extraction into saleable product, selectivity, ecological safety, the possibility of complete recovery of solvent, and absence of harmful effluents and secondary waste.

Quantitative determination of the total content of flavonoids in Flavozid and Immunoflazid syrups

New syrup compositions Flavozid and Immunoflazid that contain 2% Proteflazid (ethanol extract of wild Deschampsia caespitosa L. and Calamagrostis epigeios L.) have been developed. The total content of flavonoids in both syrups is of the level of 4 – 6 gmL, which complicates the development of an analytical method. A new method for quantitative determination of flavonoids in the aforementioned syrups has been developed on the basis of differential UV spectrophotometry of their complexes with aluminum chloride. The proposed method is introduced into the Manufacturer’s Pharmacopoeic Article for the syrups. The existing formulation of Flavozid and Immunoflazid syrups is based on the active pharmaceutical ingredient Proteflazid, which was first developed and registered in Ukraine in 2001 and is the alcohol extract of wild Deschampsia caespitosa L. and Calamagrostis epigeios L. Proteflazid prepared using the original technology was recommended for use in medical practice as a composition with direct antiviral and immunomodulating action with properties of an interferon activator and DNA protease inhibitor in virus-infected cells [1 – 3]. The principal biologically active compounds of Proteflazid are flavonoids similar to quercetin (rutin), the molecules of which are based on a flavone oxygen-containing heterocycle. However, the mixture of Proteflazid flavonoids did not contain those that are frequently used as standards. Therefore, the development of a quantitative determination method for flavonoids in the syrup, where the content of Proteflazid and the corresponding flavonoids is 2% (or 4 – 6 gmL) of the starting extract, is of definite scientific interest. The goal of our work was to develop a method that would enable quantitative determination of total flavonoids, which absorb in the UV and visible spectral regions, using aluminum chloride as a complex-forming reagent. The glycoside species were converted to the aglycons by preliminary boiling of the syrup in the presence of HCl in order to increase the total amount of flavonoids in the analytes. Acid hydrolysis of the glucosides in the syrup was carried out in an excess of conc. HCl taken at 1% of the volume of the investigated syrup. The optimum conditions for acid hydrolysis with time were determined from the degree of conversion of the glycoside component into aglycons with TLC monitoring and UV spectrophotometric data. Aglycons from the syrup were extracted by ethylacetate. Solvent was vacuum distilled until production of a pasty residue that was dissolved in ethanol (96%). Studies of the optimum conditions for complexation using freshly prepared aluminum chloride (5%) in ethanol (96%) showed that increasing the volume of the solution to greater than 1 mL in the analyte did not improve the optical density parameters of the aluminum-chloride complex of the flavonoids. The maximum optical density was retained over 25 – 40 min at wavelength 422 nm. A solution with all components of the test solution with the exception of aluminum chloride was used as a reference to compensate for absorption at 420 – 424 nm of the starting extract before complex formation with aluminum chloride. Considering the complex flavonoid composition of the starting material, known standards from various flavonoid groups were used for the quantitative determination. However, the absorption maximum of the complex with aluminum chloride of none of them agreed with that for the com

Tungstate as complex‐forming reagent facilitating separation of selected polyphenols by capillary electrophoresis and its comparison with borate

A novel electrophoretic BGE containing tungstate as complex-forming reagent is suitable for the separation of polyphenols. Similar to molybdate-containing BGE reported earlier (cf. M. Polásek, et al.., Talanta 2006, 69, 192) addition of tungstate to BGE affects significantly migration of compounds/ligands with vicinal -OH groups due to the formation of negatively charged complexes involving W(VI) as central ion. Baseline separation of mixtures of flavonoids (apigenin, luteolin, hyperoside, quercetin, and rutin) and phenolic acids (chlorogenic and p-coumaric acid) was achieved within 15 min with optimized BGE of pH 7.4 containing 50 mM N-(2-hydroxyethyl)piperazine-2'-(2-ethanesulfonic acid) (HEPES), 2.2 mM tungstate, and 25% v/v of methanol. The separation was performed in a 75 cm (effective length 42 cm)x 75 microm id uncoated fused-silica capillary at 30 kV with spectrophotometric detection at 275 nm. The calibration curves were rectilinear for 25-175 microg/mL of all analytes (cinnamic acid as the internal standard). The LODs ranged from 1.8 to 6 microg/mL for all analytes except for chlorogenic acid. Intraday precision (n = 6) of migration times (RSD < or = 1.2%) and peak areas (RSD < or = 5.6%) was evaluated. The tungstate-based BGEs can be alternatively utilized for the analysis of polyphenols at considerably lower pH than with conventional alkaline borate-based BGEs.

Sorption of mercaptanbenzothiazol and dithiophosphate on Pt-Cu-Ni minerals at flotation process

The test data on sorption and flotation properties of reagent-collectors: dithiophosphate (DTP) and mercaptanbenzothiazol (MBT) relative to Pt-Cu-Ni minerals (chalcopyrite, pentlandite, and pyrrhotite) are presented. It was established by UV-spectroscopy analysis that MBT sorption on the study mineral specimens amounted to 62 % for chalcopyrite, and 15–30 % for pyrrhotites, 88 % for pentlanditepyrrhotite specimen to the initial reagent quantity. Adsorption of isopropyl and isobutyldithiophosphate on pentlandite-pyrrhotite was 59% and 82 %, respectively, along with none actual adsorption of these reagents on pyrrhotite.. It is shown that the selective sorption of MBT and DTP proves the expediency of applying the above complex-forming reagent mixture as selective collectors for platinum-bearing sulfide minerals at Pt-Cu-Ni ore flotation.

Processing mineral raw materials in Siberia: ores of molybdenum, tungsten, lead and gold

Problems related to the processing of mineral raw materials from Siberia (i.e. molybdenum-, tungsten-, lead- and gold-containing ores and concentrates) are reviewed. It is shown that hydrometallurgical methods for processing such raw materials are more advantageous than pyrometallurgical ones. For example, hydrometallurgical treatment of molybdenum and tungsten concentrates can be used industrially. Studies have shown that the recovery and concentration of molybdenum and tungsten from leach solutions can be effectively carried out using macroporous anion exchangers. Other studies show that nitric acid/iron(III) solutions are most efficient for leaching lead from lead sulfide concentrates. Metallic lead as well as lead-containing compounds can be produced by electrolysis of lead nitrate leach solutions. These solutions also provide a hydrometallurgical method for the oxidation of pyrite and arsenopyrite in gold-containing raw materials prior to the recovery of gold by complex-forming reactants. Salt decomposition of sulfides and dissolution of gold by non-cyanide complex-forming reagents can be used also for the recovery of gold from refractory arsenopyrite concentrates. Hydrometallurgical technologies recover about 93–98% of metals. Moreover, it is quite easy to improve production efficiency by modifying the design of the industrial equipment and by preventing the formation of environmentally harmful products.

On-line microextraction of metal traces for subsequent determination by plasma atomic emission spectrometry using pH peak focusing countercurrent chromatography.

Metal ions were highly efficiently enriched by pH peak focusing high-speed countercurrent chromatography. The peak intensity for a 10-mL standard sample in the effluent stream was increased over 100-fold compared to conventional plasma atomic emission spectrometry. Ca, Cd, Cu, Mg, Mn, Ni, and Zn are chromatographically extracted in a basic organic stationary phase containing a complex-forming reagent such as bis(2-ethylhexyl) phosphoric acid. After the sample solution is introduced into the column, metal ions remain around the sharp pH border formed between acidic and basic zones, moving toward the column outlet. Enriched metal ions are finally eluted with the sharp pH border as a highly concentrated peak into a volume of less than 100 microL. We evaluated this method for concentration efficiency in trace determination in tap water using different column diameters.

Kinetics and Mechanism of the Copper(II)-Catalyzed Oxidation of the Iodide Ion by Chromate(VI) Ion in an Aqueous Solution

Abstract Although the chromate(VI) ions, CrO42− and HCrO4−, which are described as CrVI herein, could hardly oxidize the iodide ion to iodine above pH 3.0, it was catalytically oxidized by adding traces of copper(II) ion. When a copper(II) solution of 10−7—10−5 mol dm−3 was mixed with an iodide solution, after a fast formation of iodine, the iodine concentration remained constant. After such an iodine formation had occurred, if a chromate solution was added into the reacting mixture, the iodine began to form again in accordance with a rate law of 2/3(d[I2]/dt) = −d[CrVI]/dt = k[CuI][CuVI], in which [CuI] is the steady-state concentration in the chain cycle CuI+/CuI. The rate of the chain reaction was independent of the time to add chromate, and the formation of iodine I2 (or triiodide ion I3−) stopped at the time when all of the chromate was consumed by the chain reaction. The stoichiometry was 3I− + CrVI → 1.5I2 + CrIII. The iodine formation was extremely inhibited by the presence of either radical scavengers or complex-forming reagents as well as by increasing pH. Although addition of alcohols to the reaction mixture extremely accelerated the iodine formation before adding chromate, it hardly affected on this process after the addition of chromate. The reaction mechanisms are presented in order to account for the observed results.

STUDY OF ISOTACHOPHORETIC SEPARATION OF METAL IONS IN A WASTE GENERATED IN NUCLEAR FUEL CYCLE BY MEANS OF PARTICLE INDUCED X-RAY EMISSION

In order to investigate the utility value of isotachophoresis(ITP) for partitioning of a nuclear fuel waste, a model solution was fractionated using a micro-preparative apparatus. The fractions of the separated zones were analyzed off-line by means of Particle Induced X-ray Emission (ITP-PIXE) and the migration order and the recovery was evaluated. Good separability was observed when a-hydroxyisobutyric acid was used as the complex-forming reagent, confirming the practical utility of isotachophoresis for the partitioning in principle.

Diantipyrilmethane as complex-forming reagents in the thin-layer chromatographic determination of metals

The efficiency of diantipyrilmethane used as a reagent for the chromatographic separation of metals, including titanium, zirconium and hafnium, rare earth elements, transition and platinum metals is shown. The peculiarities of the chromatographic behaviour of metal diantipyrilmethanates and the mechanism of their retention in TLC are discussed. Methods were developed for the determination of metals based on complex formation directly in the sorbent layer or by liquid extraction. The chromatographic separation takes place in silica gel thin layers with elution by organic solvent-mineral acid mixtures. The metals are determined by densitometric or spectrophotometric methods. After the complexes are isolated from the layer. The procedures are characterized by simplicity, efficiency, and a rather high selectivity. They were used to analyze steels, alloys, industrial solutions and other samples.

Flavonoids of Potentilla erecta

Substance (I) C27H30016 , mp 190-192°C, [=]D 2° 108 ° (c 0.8; ethanol). Acid hydrolysis yielded the aglycon quercetin (ClsHl0OT, mp 309-311°C), while D-glucose and L-rhamnose were detected in the hydrolysate. The positions of attachment of the sugar residues to the aglycon was determined by UV spectroscopy with ionizin£and complex-forming reagents [5, 6, 8]. Alkaline hydrolysis [7] of glycoside (I) led to the formation of isoquercitrin (mp, 218-221°C, [~]D 2° -38 ° (c 0.5; pyridine) and L-rhamnose. The results obtained permitted substance (I) to be identified as quercetin 3-O-8-D-glucopyranoside 7-O-~-L-rhamnopyranoside (antoside) [4].

STUDY OF KINETIC FACTORS AFFECTING THE EFFICIENCY OF SEPARATION OF TRANSPLUTONIUM AND RARE-EARTH ELEMENTS DURING THE EXTRACTION BY DI-(2-ETHYLHEXYL)PHOSPHORIC ACID

ABSTRACT The kinetics of the extraction of transplutonium and rare-earth elements with HDEHP from solutions of different complex-forming reagents has been studied. The possibility of the Improvement of intragroup separation of these elements with the use of dynamic factors has been demonstrated

Exchange extraction equilibrium of mercury(II) and bis(diethyldithiocarbamato)copper in sub-and superequivalent method of isotope dilution analysis

Bis(diethyldithiocarbamato)copper, Cu(dedtc)2 in tetrachloromethane was applied as a complexforming reagent in sub- and superequivalent method of isotope dilution analysis for the determination of active and inactive mercury in the 1–30 μg mercury concentration range in a pH 4.6 acetate buffer.

A dithizone post-column detector for the high-performance liquid chromatographic determination of trace metals

A multi-element post-column high-performance liquid chromatographic detector based on dithizone as a complex-forming reagent is described. The separation was achieved in aqueous media on a sulphonated 10% cross-linked polystyrene resin. Cadmium(II), cobalt(II), copper(II), lead(II), nickel(II) and zinc(II) ions were detected down to nanogram levels. Working ranges up to the microgram level were possible. The use of this heavy metal detector which may be tuned by pH control 1 is discussed. An advantage of the system for multi-element determinations is that the decrease in the dithizone absorbance at 590 nm is measured rather than increased absorbances at different wavelengths particular to each metal dithizonate.

High-performance liquid chromatography of inorganic anions using Fe 3+ as a detection reagent

Fe 3+ was examined as a detection reagent in the analysis of inorganic anions by high-performance liquid chromatography. The chromatographic conditions were: the stainless-steel tube was packed with TSK-GEL IEX-520 QAE: 0.05 M sodium acetate buffer (pH 5.48) containing 0.05 M sodium nitrate was used as eluent; and 0.08 M perchloric acid containing 0.05 M iron(III) perchlorate was chosen as a complex-forming reagent. Under these conditions, chloride, sulphate and thiocyanate ion were determined in the range 2-500 nmol, and phosphate, nitrite and thiosulfate ion in the range 8-500 nmol.

Complex formation of iron(II) with 2-pyridine-aldehyde-2'-benzothiazolylhydrazone

Although 2-pyridinealdehyde-2'-benzothiazolylhydrazone (PABH) has been known well as a complex-forming reagent for iron (III), its complex with iron (II) has scarecely been known yet. The authors have found that PABH reacts with iron (II) as well as iron (III) to form a water-insoluble yellow complex in the aqueous solution. The iron (II) compiex is quantitatively extracted into benzene in the pH range of 4.29.4. The extracted complex was found to be diamagnetic species from the analysis of NMR spectra, and the oxidation state of iron in it was +2 from the analysis of X-ray photoelectron spectra. The combining ratio of iron (II) to PABH in the complex was estimated to be 1 : 2 by the continuous variation method. On the basis of these results, it was assumed that the structure of the extracted complex was the octahedral configuration.

ChemInform Abstract: ANALYSIS OF METALS BY SOLID‐LIQUID SEPARATION AFTER LIQUID‐LIQUID EXTRACTION, SPECTROPHOTOMETRIC DETERMINATION OF SOME METALS BY EXTRACTION OF METAL COMPLEXES WITH MOLTEN NAPHTHALENE

AbstractEinige Metallionen (Cu, Zn, Mg, Cd, Ni) bilden mit Oxin, 2‐Methyl‐oxin"Dimethylglyoxim oder α‐Benzil‐dioxim in bestimmten pH‐Bereichen wasserunlösliche Komplexe die sich leicht mit geschmolzenem Naphthalin extrahieren lassen.

Analysis of Metals by Solid-Liquid Separation after Liquid-Liquid Extraction. Spectrophotometric Determination of Some Metals by Extraction of Metal Complexes with Molten Naphthalene

Abstract A procedure is described for the spectrophotometric determination of metals after extraction with molten naphthalene. Some metal ions react in aqueous solution with complex-forming reagents such as oxine, 2-methyl-oxine, dimethylglyoxime or α-benzil dioxime to form water-insoluble complexes in certain pH ranges, the complexes being easily extracted into molten naphthalene. The extracted mixture of metal complex and naphthalene is dissolved in dimethylformamide and the amount of each metal is determined spectrophotometrically. The working range of metal ion concentration and effect of various factors such as pH, amount of reagent and naphthalene were studied, and the molar absorptivity, sensitivity and relative standard deviation evaluated.