Stopped-flow kinetic determination of aluminum in Chinese tea leaves by fluoride ion-selective electrode potentiometry

A stopped-flow kinetic potentiometric method for the determination of aluminum is described, based on monitoring the reaction between aluminum and fluoride at pH 3.0 using fluoride ion-selective electrode. The initial rate of the reaction is proportional to the concentration of aluminum present in the solution. The method is simple and rapid and has been applied to the determination of aluminum in Chinese tea leaves after microwave digestion.     

微波消解-原子吸收法测定氧化铝为载体的钯催化剂中钯

报道了微波消解-AAS法测定氧化铝为载体的钯催化剂中钯的新方法,试验了微波消解溶样条件（溶解试剂、压力、时间和功率等）,研究了测定介质的影响,通过在样品测定液中加入铝基体至铝浓度为4 mg/mL,消除了铝对钯测定的干扰.该法测定结果与光度法的结果一致,相对标准偏差小于1.5%（n=5）.     

抑制褪色光度法测定油炸面制食品中痕量铝

建立抑制褪色光度法快速测定食品中痕量铝的方法。在硫酸介质中,一定量的铝离子对溴酸钾氧化罗丹明B褪色有抑制作用,据此建立了抑制褪色光度法快速测定食品中痕量铝的新体系,最大吸收波长为550 nm。在1 mol/L硫酸介质中,铝含量在0.07~0.4μg/mL范围内与吸光度具有良好的线性关系,相关系数r=0.9995,检出限为0.02μg/mL。用该方法测定油炸面制食品中痕量铝,测定结果的相对标准偏差为1.3%~3.1%(n=11),加标回收率为99.3%~103.5%。该方法测定结果准确可靠,可用于食品中痕量铝的测定。     

Determination of zeolite-a in detergent powders as acid-soluble aluminum by high-performance liquid chromatography with post-column derivatization

A high-performance liquid chromatographic method is described for the rapid determination of zeolite-A in detergents as acid-soluble aluminum. Detergent samples are dissolved by digestion with nitric acid. Chromatographic separation on a strong cation exchanger in acidic ammonium sulfate media is combined with the highly selective color reaction of acid-soluble aluminum with pyrocatechol violet. Interferences of the chelating agents in detergents are thus eliminated. After the digestion, determinations take 8 min per sample. The relative standard deviation is less than 1% and quantitative recoveries are obtained. Several commercial detergents were analyzed successfully. The results obtained by the proposed method and by compleximetric titration agreed very closely for zeolite-A contents in the range 2–22%.     

Large-scale preparation of aluminum borate-coated aluminum oxide nanowires

Single-crystal and uniform aluminum borate (Al₄B₂O₉)-coated aluminum oxide nanowires have been synthesized in high purity and in large yield via a reaction of metal aluminum with boron oxide in the presence of carbon nanotubes (CNTs). The aluminum oxide nanowires exhibit a well-crystallized one-dimensional structure with diameters ranging from 50 to 70 nm, and the Al₄B₂O₉ have a coating thickness of about 1-5 nm. CNTs play a crucial role in the formation of the important ceramic nanowires, by providing a platform to grow the composite structure. The growth mechanism was proposed by the detailed microscopy observations.     

炼铝用碳阳极中碱金属氧化物作用机理的量子化学研究

本文应用CNDO/2法研究了炼铝用碳阳极中添加碱金属氧化物的吸附行为, 通过优化得到了吸附的最佳模型, 考察了吸附结合能随分子间距的变化, 进而给出了碱金属氧化物在碳阳极中作用的机理。量子化学计算结果表明: 碱金属氧化物添加到炼铝用碳阳极中起传输电子的电桥作用, 是碳阳极在空气中氧化反应以及铝电解时生成氧气的氧化反应的催化剂; 理论计算和实验结果二者吻合较好, 可以用来解释若干实验结果。     

Standardization of aluminum oxide and detection of polycyclic aromatic hydrocarbons on aluminum oxide

Luminescence methods are described for detecting polycyclic aromatic hydrocarbons (6-, 5-, 4-, and 3-ring) on aluminum oxide after separation by dry-column chromatography. A method is reported for standardizing the water content in the aluminum oxide used for dry-column chromatography. A water content of 4.74% was chosen to define the activity of aluminum oxide because there was minimum overlap among the PAH bands.     

Toward a quantitative description of the anodic oxide films on aluminum

A method to quantify the composition of anodic oxide films on aluminum using Infrared Spectroscopic Ellipsometry (IRSE) is proposed. It consists of obtaining the absorption coefficient of the film as a function of wavelength. Using values of the absorption coefficients for the pure components of the film, the percentages (mole or wt%) of each component in the sample can be calculated.The method is demonstrated in a study of the structure of the oxide film on electropolished aluminum and the anodically formed barrier layer film. Both surface oxides were found to be initially a form of amorphous Al₂O₃. While the barrier film is essentially free of water as prepared, the film on electropolished aluminum contained about 25 wt% water. Hydration of both types of films by immersion in boiling water results in the formation of pseudoboehmite (AlOOH). The technique may have more general applicability to the quantitative determination of the composition of corrosion films and other surface layers on metals.     

Structure of castable polyurethanes filled with aluminum oxide

The structure and properties of castable polyurethanes with different content of the aluminum oxide filler were studied by X-ray diffraction, electron microscopy, and determination of the apparent cross-link density.     

Removal of phosphate by aluminum oxide hydroxide

The development and manufacture of an adsorbent to remove phosphate ion for the prevention of eutrophication in lakes are very important. The characteristics of phosphate adsorption onto aluminum oxide hydroxide were investigated to estimate the adsorption isotherms, the rate of adsorption, and the selectivity of adsorption. Phosphate was easily adsorbed onto aluminum oxide hydroxide, because of the hydroxyl groups. The adsorption of phosphate onto aluminum oxide hydroxide was influenced by pH in solution: the amount adsorbed was greatest at pH 4, ranging with pH from 2 to 9. The optimum pH for phosphate removal by aluminum oxide hydroxide is 4. The selectivity of phosphate adsorption onto aluminum oxide hydroxide was evaluated based on the amount of phosphate ion adsorbed onto aluminum oxide hydroxide from several anion complex solutions. It is phosphate that aluminum oxide hydroxide can selectively adsorb. The selectivity of phosphate onto aluminum oxide hydroxide was about 7000 times that of chloride. This result indicated that the hydroxyl groups on aluminum oxide hydroxide have selective adsorptivity for phosphate and could be used for the removal of phosphate from seawater.     

Interactions of hydrosiloxane and vinylsiloxane groups with aluminum oxide surfaces

Silicone-based materials often contain vinylsiloxane and hydrosiloxane groups for cross-linking by a radical or addition reaction. Such functional groups can influence the interactions with fillers or with surfaces of substrates when used as adhesives. This work examined how these functional groups interact with aluminum oxide surfaces. For this purpose, aluminum oxide powders with large surface areas of 150 m²/g and different acid-base properties were examined. Siloxanes were applied as thin layers to mainly obtain information from the interphase by vibrational spectroscopy. It was observed that vinyl groups show low interactions with aluminum oxide surfaces even at elevated temperatures. In contrast to this, hydrosiloxanes undergo strong interactions and reactions with aluminum oxides already at room temperature. Activated Si─H species were observed as an intermediate state. On the one hand, interactions and reactions might contribute to adhesion, but on the other hand, the cross-linking reaction can be influenced near the surface, leading to lower mechanical strength.     

A novel method for the preparation of diborane from aluminum,ethyl chloride,boron oxide and hydrogen

A novel method is described for the preparation of diborane from aluminum, ethyl chloride, boron oxide and hydrogen via three steps; deoxyalkylation of boron oxide, hydrogenation of triethylboron and liberation of diborane. The triethylboron was prepared from aluminum, ethyl chloride and boron oxide directly at 85–110°C in 88% yield, with aluminum trichloride as by-product in 95% yield. In the presence of triethylamine and a hydrogen pressure of 130 kg/cm², the triethylboron was hydrogenated at 200°C for 2 hours to produce borane-triethylamine complex in 92% yield. The borane-triethylamine complex was treated again at 80°C with the aluminum trichloride collected from the first step to liberate diborane in 94% yield. The overall reaction yield was 76%.     

Spectrophotometric determination of aluminum and iron in calcium

A simple, rapid, and accurate method is described whereby micro amounts of aluminum and iron can be determined in calcium metal. The iron is determined spectrophotometrically by measuring the absorbency of the reddish-orange color of the tris(1,10-phenanthroline)iron(II)ion, [(C₁₂H₈N₂)₃Fe]⁺⁺. This complex effectively removes the iron interference, and the aluminum is determined spectrophotometrically in the solution remaining from the iron determination by extracting it with a chloroform solution of 8-quinolinol and measuring the absorbency of the yellow color of the tris(8-quinolinolo)aluminum(III) in the chloroform solution.     

Flow-Injection Biamperometry of Phenol

ABSTRACT

A simple and rapid method determination of phenol is described, using a bromination reaction and biamperometric detection. The method is based on measurements of the intensity of current passing through two identical inert electrodes giving the concentration of phenol in samples. The sample is injected into a stream of carrier and merged with a stream of acidic bromine solution which brominates phenol in the reaction coil. A linear relationship between peak height and phenol concentration is observed in the range of 0.05 to 8 μg ml^?1 of phenol. The relative standard deviation was 2.8% for analysis of 5μg ml^?1 phenol and the sampling rate was 70 h^?1     

Determination of trace aluminum by fluorescence quenching method based on catalysis of potassium chlorate oxidizing alizarin red

A new method for the determination of trace aluminum has been proposed. It is based on the fact that alizarin red can emit strong and stable fluorescence at 80 degrees C for 30 min and Al(3+) can effectively catalyze potassium chlorate oxidizing alizarin red to form non-fluorescence complex which cause the fluorescence quenching. The linear dynamic range of this method is 0.040-4.00 ngl(-1) with a detection limit of 5.3 pgl(-1). The regression equation can be expressed as DeltaI(f)=8.731+21.73c(Al(3+)) (ngl(-1)), with the correlation coefficient r=0.9992 (n=6). This sensitive, rapid and accurate method has been applied to the determination of trace aluminum(III) in human hair and tea samples successfully. What is more, the mechanism of catalyzing potassium chlorate oxidizing alizarin red by the fluorescence quenching method is also discussed.     

Synthesis and purification of aluminum isopropylate

Possibility of deep purification of lower aluminum alcoholates used to synthesize aluminum oxide by the sol-gel method and pyrolytic technique is analyzed. The influence exerted by the purity of the starting reagents, moisture content, and catalyst on the nature of the process and the purity of the product being obtained was examined.     

痕量苯酚的单扫描极谱法测定

研究了碱性介质中苯酚与对氨基苯磺酸重氮盐所形成偶氮化合物的极谱行为，并建立了痕量苯酚的极谱测定方法。方法用于污水中微量苯酚的测定，结果令人满意。     

Simultaneous determination of trace iron and aluminum by catalytic spectrophotometry based on a novel oxidation reaction of xylene cyanol FF.

A new, simple, sensitive and selective method for the simultaneous determination of trace iron and aluminum by catalytic spectrophotometry was presented, based on the catalytic effects of iron and aluminum on the discoloring reaction of xylene cyanol FF proceeded by hydrogen peroxide and potassium periodate in weak nitric acid medium. No catalytic effect was obtained in the presence of hydrogen peroxide or potassium periodate only. With the conditional rate constants determined in reaction systems catalyzed by Al or Fe only, the concentrations of Fe and Al in the samples can be calculated. The method was applied to the simultaneous determination of trace Fe and Al in tap water, lake water, river water and tea leaves without separation and preconcentration.     

Preconcentration of metal ions on aluminum oxide modified with tiron

It is found that iron(III), titanium(IV), vanadium(V), copper(II), lead(II), and zinc(II) ions are adsorbed on aluminum oxide modified with Tiron. The adsorption of iron(III) is accompanied by the violet coloration of the adsorbent (560 nm), which indicates the formation of a 1: 2 complex on the adsorbent surface; copper forms a 1: 1 yellowish green complex (430 nm). The group preconcentration of metal ions on this adsorbent in a dynamic mode is possible; the preconcentration rate is 2.5 × 10³. The method for the determination of metal ions is proposed based on the adsorption recovery of the elements followed by the direct determination by X-ray fluorescence spectroscopy on the adsorbent surface.     

Interference of aluminum chloride and nitrate on alkaline earth elements in an air-acetylene flame

Aluminum nitrate causes a strong interference in the determination of alkaline earth elements in the air-acetylene flame by formation of mixed oxides, predominantly of the spinel-type M^IIAl₂O₄. The influence of aluminum chloride is less pronounced because the analyte chloride must be converted to the oxide before it reacts with aluminum oxide. Any compound that delays the formation of oxides hence alleviates the depressing effect of aluminum. Particle size plays a decisive role in the sensitive equilibrium between alkaline earth chloride and oxide formation. Aluminum chloride hexahydrate hydrolyzes on desolvation in the flame, giving off HCl. This way an atmosphere of HCl is generated inside larger particles that isolate the analyte from oxygen in the flame gases and favor formation of thermally less stable chlorides, and hence atomization. Addition of an excess of cesium chloride increases the average particle size further and supports that mechanism. Moreover, cesium chloride causes an early disintegration of large particles releasing analyte chlorides into the flame, thus enhancing their degree of atomization.