Photometric determination of gallium in the presence of aluminum

The complexation of gallium(III) with 2,2′,3,4-tetrahydroxy-3′-sulfo-5′-nitrobenzene in the presence of and without 1,10-phenanthroline was studied. In the presence of 1,10-phenanthroline, a mixed-ligand complex with the component ratio 1:2:1 and the stability constant logβ = 15.5 ± 0.2 is formed. The effect of pH, time, temperature, and the concentration of components on the formation of the binary and mixed-ligand complexes of gallium was studied. A procedure was developed for the photometric determination of gallium(III) in the presence of aluminum (III).     

Gallium extraction by microemulsions

In this work, the use of microemulsion in the extraction of gallium, with Bayer process, has been studied. The studied microemulsion systems were: systems I and II, with saponified coconut oil (SCO) and 4-ethyl,1-methyl,7-octyl,8-hydroxyquinoleine (Kelex-100) as extractants. The extraction essays by microemulsion were carried out by applying an experimental planning method whose microemulsion points were prepared within an experimental domain favorable to the extraction. Gallium and aluminum extraction percentages, in each point, were evaluated via a statistical treatment of the data, with the use of variance analysis and mathematical models. In system I (SCO), percentages of extraction of 85.5% for gallium and 35.4% for aluminum were achieved; in system II (Kelex-100), the yields were 100% for gallium and 99.9% for aluminum. The reextraction study with sulfuric acid presented the same behavior for both systems, with efficiency depending upon the concentration of the acid, and allowing for a selective reextraction of gallium and aluminum.     

Influence of temperature and humidity on the degradation process of ascorbic acid in vitamin C chewable tablets

Ascorbic acid (AA) is the active ingredient of vitamin C chewable tablets. It is unstable even at room temperature, and increased temperature and humidity rapidly increase its degradation. To protect the active substance, we made its coating with polymers ethyl cellulose that provides its thermal protection and protection from moisture. We bet each particle of AA with a layer of polymer by the method of fluidization. Extra protection against thermal effects and penetration of moisture and oxygen provides the packaging. By using four kinds of packaging: polypropylene container for tablets, strips of aluminum and polyvinyl chloride Al/PVC strips, glass bottles, and strips of aluminum and polyethylene (Al.PE/PE.Al) of 3, of 6 months and of 12 months. One of the tablets are stored at room temperature (25 ± 2 °C/60% RH ± 5%), and the rest in terms of accelerated aging or increased temperature and humidity (30 ± 2 °C/65% RH ± 5% and 40 ± 2 °C/75% RH ± 5%). The speed of degradation of unprotected AA usually get doubled when there is increasing of the temperature for every 10 °C. Experimentally the concentration of AA was monitored, its oxidation product-dehydroascorbic acid and its degradation product-diketogulonic acid.     

New developments in the chemistry of organoaluminum and organogallium hydrides

A survey of our recent work on organoaluminum and organogallium hydrides is presented. Three types of ligand system have been employed for the stabilization of monomeric aluminum and gallium mono- and dihydrides. The “two-armed” 2,6-bis (dimethylaminomethyl) phenyl ligand is effective when intramolecular bis(base) stabilization is necessary; its use has permitted the isolation of the first examples of monomeric aluminum and gallium dihydrates. The use of the corresponding “one-armed” 2-(dimethylaminomethyl) phenyl ligand resulted in the formation of gallium mono- and dihydride monomers and an aluminum dihydride dimer. The first base-free aluminum and gallium monohydrides and gallium dihydride have been stabilized by employing the bulky 2, 4, 6, -tris(t-butyl) phenyl ligand.     

Improved Determination of Aluminum in Serum by Electrothermal Atomic Absorption Spectrometry and Zeeman Background Correction

Abstract

A simple but reliable method for the determination of aluminum in serum by flameless atomic absorption spectrometry is described. By use of the Zeeman background correction, the interferences are eliminated. However, considering the numerous possible sources of contamination, extreme precautions are necessary both when taking and storing the serum. The procedures preceding the dosage per se must be minimized. The within-day and clay-to-day precision data (CV %) was 3.28 and 3.82 respectively. The average recovery for aluminum was 97.5 %. We used this method on serum from 30 healthy subjects and from 300 patients on hemodialysis. The mean aluminum concentration for the healthy subjects was 5.35 μg/l (SD ± 0.53) while the values for the hemodialyzed patients ranged from 20 to 220 μg/l.     

Internal standard method for determination of gallium and some trace elements in bauxite by neutron activation analysis

A method is described for the determination of gallium and other trace elements such as Ce, Cr, Hf, Lu and Th in bauxite by the technique of neutron activation analysis using gold as internal standard. Isopropyl ether was used as organic extractant to extract radioactive gallium from the sample. This method yields very good accuracy with a relative error of ±3%.     

Analysis of Borosilicate Catalysts by Inductively Coupled Plasma Atomic Emission Spectroscopy

Abstract

A method was developed for the analysis of borosilicate catalysts. Samples were prepared by fusion technique with potassium hydroxide and analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The method was applied to a borosilicate NIST SRM 93 which was analyzed for major and minor elements (aluminum, sodium, silicon and boron). Despite the presence of relatively high concentration of the potassium, no matrix interferences were observed. This method provides precision and accuracy better than ±4% and ±6%, respectively.     

Theoretical study on reactions catalyzed by gallium-substituted zeolites

The dehydrogenation and cracking reactions of light alkanes in gallium-containing zeolites were studied using density functional theory. Gallium isomorphically substituted, generating Brønsted acid sites, was used in the computations. The following reactions were examined: dehydrogenation of methane, ethane, propane, isobutane and cracking of ethane, propane and isobutene, all catalyzed by the framework gallium species. The cracking reaction seems to be favored relative to the dehydrogenation when framework gallium species are used. This behavior is also observed in aluminum-containing zeolites (H-ZSM5). The geometries and energetics of the transition states found for the gallium zeolites were compared with theoretical data for the same transition states in aluminum zeolites. There seems to be no significant difference between framework gallium and framework aluminum species. Therefore the framework gallium should not be the species responsible for the catalytic enhancement observed in gallium-containing zeolites.From the Proceedings of the 28th Congreso de Químicos Teóricos de Expresión Latina (QUITEL 2002)     

A kinetic study of the reactions of the hydrogen atom with the cyclohexadiene isomers in the gas phase

Absolute values of the rate constants for the reaction of hydrogen atoms with cyclic olefins in the gas phase have been measured in a discharge-flow system under 3.5, 16, and 22 torr Ar at 23°C. The attenuation of hydrogen atom concentration in the reaction tube in the presence of a large excess of olefin was measured with an ESR spectrometer, and the products were analyzed by gas chromatography. Cyclic C₆ hydrocarbons were the only significant products obtained when the hydrogen atom concentration was 2.6 × 10^?10 mole/1., the olefin concentration was in the range of 9 to 22 × 10^?8 mole/1., and the pressure was 16 torr Ar. The values for the rate constants for reaction with cyclohexadiene-1,3, cyclohexadiene-1,4, and cyclohexene are, respectively, (9 ± 2) × 10⁸, (12 ± 1) × 10⁸, and (6 ± 1) × 10⁸ l./mole-sec, and they are not changed significantly by a sixfold change in total pressure. The fraction of the total interaction that proceeds by addition is 84% in the cyclohexadiene-1,3 system, but only 18% in the cyclohexadiene-1,4 system, and the cyclohexadienyl radical is therefore the dominant radical species in the latter system. The pattern of interaction between the hydrogen atom and the cyclohexadienyl radical was determined, and comprises 65% of disproportionation, and 13% and 23% of combination to yield cyclohexadiene-1,3 and cyclohexadiene-1,4, respectively. These results are consistent with the general patterns of reactivity emerging from studies of the reactions between free radicals and olefins in related systems.     

A facile method for fabrication of superhydrophobic coating on aluminum alloy

A superhydrophobic coating applied in corrosion protection was successfully fabricated on the surface of aluminum alloy by chemical etching and surface modification. The water contact angle on the surface was measured to be 161.2° ± 1.7° with sliding angle smaller than 8°, and the superhydrophobic coating showed a long service life. The surface structure and composition were then characterized by means of SEM and XPS. The electrochemical measurements showed that the superhydrophobic coating significantly improved the corrosion resistance of aluminum alloy. The superhydrophobic phenomenon of the prepared surface was analyzed with Cassie theory, and it was found that only about 6% of the water surface is in contact with the metal substrate and 94% is in contact with the air cushion. Copyright © 2011 John Wiley & Sons, Ltd.     

Spectrophotometric and thermal lens determination of aluminum with 3-sulfo-5-nitro-4′-diethylamino-2,2′-dihydroxyazobenzene

The conditions of the spectrophotometric and thermal lens determination of aluminum with sulfo-5-nitro-4′-diethylamino-2,2′-dihydroxyazobenzene have been compared. The limit of spectrophotometric detection of aluminum in aqueous solutions has been found to be 8 ng/mL. On the basis of the conditions of spectrophotometric determination, the conditions for thermal lens determination have been proposed (532.0 nm, exciting radiation power of 42 mW); they provide a decrease of the detection limit down to 0.6 ng/mL and an increase of the sensitivity coefficient by an order of magnitude. It has been shown that, in the case of the thermal lens determination of aluminum in water-organic mixtures (50 vol % of dimethyl sulfoxide or 30 vol % acetonitrile), the sensitivity coefficient is respectively 9.1 and 6.3-fold higher as compared with the thermal lens determination in water. As a result, the detection limits are reduced 2.5 and 10-fold, respectively. Aluminum has been determined by thermal lens spectrophotometry in Moscow’s tap water using the standard addition method, its concentration being 0.79 ± 0.07 mg/L, which is above the threshold limit value of the aluminum content of drinking water.     

Gallium-containing catalysts for oxidative dehydrogenation of organic compounds

A method was developed for introducing gallium into Mg-Al hydrotalcites—precursors of oxide catalysts for oxidative dehydrogenation of alkanes. Samples of oxide catalysts were synthesized that contained gallium oxide and also oxides of magnesium, aluminum, chromium, vanadium, molybdenum, and niobium in various combinations. The catalytic properties of the produced catalysts were studied in the oxidative dehydrogenation of ethane, propane, isobutane, and hexane. It was established that the addition of gallium to catalysts increases the ethylene and propylene yields in the oxidative dehydrogenation of ethane and propane. New hydroxo salts with a layered structure of the hydrotalcite type were synthesized: ternary magnesium gallium aluminum hydroxonitrate of variable composition [Al_{1 ? n} Ga _n Mg _m (OH)_{3 + 2m ? 1}][NO₃ · nH₂O] and quaternary magnesium gallium chromium aluminum hydroxonitrate of the composition [AlGaCrMg_1.8(OH)_11.6][NO₃ · nH₂O]; these salts were found to be isostructural.     

Determination of gallium by square-wave voltammetry anodic stripping, based on the electrocatalytic action of 2,2'-bipyridine in dimethylsulphoxide: comparison with an aqueous NaSCN/NaClO(4) electrolyte

Deposition potential, deposition time, square-wave frequency, 2,2'-bipyridine concentration, and gallium concentration have been studied in detail, for the determination of trace concentration levels of the metal by square-wave voltammetry anodic stripping analysis, in dimethylsulphoxide. Optimum conditions have been found for gallium(III) determination and results compared to those obtained in 0.5M NaSCN + 4.2M NaClO(4) aqueous electrolyte by obtaining calibration graphs for the range 1 x 10(-8)M-1 x 10(-5)M gallium. Accuracy (+/- 3%) and precision (4-6% SD) of this method were assessed with both 4 x 10(-8)M and 4 x 10(-7)M gallium solutions used as synthetic samples. The efficiency of solvent extraction of gallium with di-isopropyl ether was found to be 99.98% at a 4 x 10(-7)M gallium concentration. The proposed method was applied to the determination of the gallium content in rock mineral samples (using the above mentioned solvent extraction procedure), are compared to those obtained with the NaSCNNaClO(4) based electrolyte. No statistically significant difference was observed. Analytical procedures followed are given in detail.     

负载PtSn金属助剂的镁铝水滑石上的丙烷脱氢反应研究

我们研究了以镁铝水滑石作为载体,利用水滑石层间阴离子的可交换性,负载活性金属铂和锡的丙烷脱氢反应.在镁铝水滑石载体中加入Ga能够影响丙烷脱氢活性,当镓的含量为1%时催化剂丙烷脱氢反应活性最高,反应初始时,丙烷转化率为46.5%,反应2 h后,丙烷转化率仍有37.5%.当以Mg(Ga)(Al)O-1%为载体时,考察了不同H_2/C_3H_8摩尔比对丙烷脱氢活性的影响,结果表明当H_2/C_3H_8摩尔比为0.5∶1时,丙烷脱氢反应具有最佳的反应活性,即当在原料气中加入H_2时,能够使得丙烷脱氢的转化率大幅度提升,且选择性也有所提升.烷烃脱氢是一个吸热反应,同时考察了温度对烷烃脱氢反应性能影响,结果表明温度越高,丙烷脱氢反应具有更高的转化率.对催化剂进行长时间寿命实验考察,发现当反应经过40 h后,丙烷的转化率仍有23.5%,说明Pt Sn-Mg(Ga)(Al)O-1%催化剂具有较好的稳定性.     

Kinetics of the reaction of aluminum EDTA and cobalt(II) EDTA with calmagite

The reaction of aluminum EDTA with calmagite was found to be first-order in calmagite, half-order in aluminum EDTA, and zero-order in excess EDTA. The three-halves-order apparent rate constant at pH 9.48 and 20°C with ionic strength 0.30 was 0.232 ± 0.0141^{$\text{1}\text{2}$} · mol^{$\text{1}\text{2}$} · s^?1. The activation energy was 3.2 ± 0.3 kcal/mol. The pH dependence was complex between 8 and 10. The mechanism proposed is a rapid dissociation of a dimer of aluminum EDTA to a monomer followed by a rate-determining displacement of the EDTA by calmagite. The reaction of Co(II) EDTA with calmagite was confirmed to be first-order in Co(II) EDTA and first-order in calmagite with an activation energy of 7.5 ± 0.6 kcal/mol.     

A wet chemical preparation of transparent conducting thin films of Ga-doped ZnO nanoparticles

Crystalline gallium doped zinc oxide (GZO) nanopowders were synthesized using hydrothermal treatment processing. The doping concentration affected the phase structure as well as the shape of the nanopowder from nano rod-like structure to nanoparticulate one. The specific BET surface area increases with increasing the gallium doping concentration. Transparent conducting films were deposited on borosilicate glass substrate by spin coating using sols containing GZO nanoparticles dispersed in 1-propanol. The films are crystalline with a hexagonal structure. The effect of Ga doping concentration, sintering temperature and thickness of the layers has been investigated. The lowest resistivity achieved was 6.4 × 10^?2 Ω cm for a thickness of 150 nm. The films present a transmittance in the visible range as high as 90 %.     

Simultaneous Determination of Gallium(III) and Indium(III) in Urine and Water Samples with Cloud Point Extraction and by Inductively Coupled Plasma Optical Emission Spectrometry

A simple, sensitive, and selective method for the determination of gallium and indium in different samples at trace levels is presented. This method was based on complexation of analyzes with 2-(5-bromo-2- pyridylazo)-5-diethylaminophenol (5-Br-PADAP) in the presence of t-octylphenoxy-polyethoxyethanol (Triton X-100). After phase separation, the analyzed concentrations were determined by inductively coupled plasma optical emission spectrometry. Quantitative extraction of gallium and indium was performed at pH 7.0, 1.7 mmol L^?1, 5-Br-PADAP, 1.3% (w/v) Triton X-100 and at 75°C. The relative standard deviations (RSD) of this method were between 0.3% and 1.6% (C = 20 ng mL^?1, n = 9). The calibration curve is linear over the concentration range 6–200 ng mL^?1 for gallium and 2–200 ng mL^?1 for indium, respectively. The limits of detection (LOD) for gallium and indium were 0.72 and 0.28 ng mL^?1, respectively. The results showed the developed method was not susceptible to matrix effects, providing recoveries between 98% and 102%. The accuracy of the developed method was evaluated by the analysis of spiked certified reference materials. The developed method was successfully applied to gallium and indium determination in urine and lake water with satisfactory results.     

Determination of Aluminium by Electrothermal Atomization Atomic Absorption Spectrometry in Serum to Characterize Hemodialysis Toxicity

A simple and cost-effective method is described for the determination of aluminum by electrothermal atomic absorption spectrometry (ET-AAS) in serum of hemodialysis patients and healthy subjects. The only preparative step required is the dissolution of the serum sample in 0.2% magnesium nitrate matrix modifier and separate diluents 0.01 M EDTA and 0.1% Triton X-100. The calibration curve was linear from 20 to 100 µg/L with correlation coefficients of 0.9993 and 0.9998 for EDTA and Triton X-100, respectively. The sensitivity of the method for aluminum at the 309.3 nm line was 74 pg. The instrumental and method limits of detection were 2.2 µg/L and 4.4 µg/L, respectively. The aluminum concentrations of forty serum samples from hemodialysis patients and healthy subjects were determined and the mean values were 170.9 ± 6.8 µg/L and 47.3 ± 9.3 µg/L, respectively, whereas the permissible limit for aluminum in blood serum is 10 µg/L. The high level of Al in serum was related to oral phosphate binding agents and dialysis treatment.     

Control of the composition of lanthanum gallium silicate by laser ablation inductively coupled plasma mass spectrometry

The possibilities of determining the impurities and basic components of lanthanum gallium silicate using laser ablation in combination with inductively coupled plasma mass spectrometry (LA-ICP-MS) were shown. A procedure for the determination of 54 impurity elements with the limits of determination from n × 10^?5 wt % for Mg, Ti, V, Cr, Mn, Ni, Cu, and Zn to 2 × 10^?7 wt % for U and also a procedure for the determination of a ratio between basic components were developed. It was found that the concentration ratios between gallium and lanthanum and silicon and lanthanum in the crystals of lanthanum gallium silicate remained constant upon consecutive melting operations with the addition of a charge mixture to the crucible.     

Extraction and spectrophotometric determination of gallium with 4-(2-pyridylazo)resorcinol

A sensitive and selective spectrophotometric determination of gallium is described. It is based on extraction of gallium from 3 M hydrochloric acid solution as a chloro-complex into 1,2-dichlorobenzene and exchange of the chloro ligand with 4-(2-pyridylazo)resorcinol (PAR); the final association complex of Ga—PAR with tetraphenylarsonium ions is measured in the organic phase. The absorption maximum occurs at 510 nm and the effective molar absorptivity is (8.2 ±0.3) ·1O⁴ l mol^-1cm^-1. Beer's law is obeyed over the range 0.2–2 p.p.m. of gallium. Few ions interfere.