Analytical applications of condensed phosphoric acid-II: determination of aluminium, iron and titanium in bauxites after decomposition with condensed phosphoric acid

Bauxites can be decomposed by condensed phosphoric acid (CPA) very rapidly without the need for subsequent manipulations such as elimination of silica, digestion of fused products and filtration. It is best to heat the samples at about 700 degrees prior to the decomposition, to prevent them from floating on the surface of the CPA. Under the proposed conditions (100 mg of sample, 10 g of CPA, heating at 300 degrees for 30 min), aluminium, iron and titanium are dissolved quantitatively. Iron is determined by photometry with 1,10-phenanthroline after solvent extraction with MIBK, while titanium is determined with N-benzoyl-N-phenylhydroxylamine (BPHA). The effect of phosphate on the determination of titanium is reduced to a minimum at a BPHA concentration of 0.3% and a hydrochloric acid concentration of 7.2M. Aluminium and iron are precipitated quantitatively as the oxinates at pH 5.5 in the presence of orthophosphoric acid or hydrolysed CPA, while the precipitation of titanium oxinate is completely suppressed by the addition of hydrogen peroxide. The total amount of aluminium and iron is obtained by determining the amount of oxine by bromination method. The amount of aluminium is obtained by subtracting the amount of iron from the sum of the two.     

Atomabsorptionsspektrometrie mit verdampfung fester Proben durch laserstrahlung—II. Analytische anwendungen

The use of a pulsed neodymium laser permits the direct analysis of solids (metallic and non-metallic) that cannot be analyzed by flame or oven AAS without preparation of the specimen. Microgram quantities are vaporized and partly atomized by the focused laser radiation. AAS techniques are used to investigate the freely expanding vapour of the sample by space and time resolution. The analytical application of this procedure is demonstrated by the determination of the trace constituents Cu, Mn, Mg, Fe, Zn and Si in aluminium and of Cu and Mn in steel.The analytical capability of this method is compared to other AAS techniques. The relative detection limits of ～ 10^?6 g g^?1 for Cu, Mn and Mg in aluminium agree with results obtained on similar samples using flame AAS. The absolute detection limits of ～ 10^?10 to 10^?11 g for these elements approach the values obtained in furnace AAS. The precision is limited by fluctuations in the laser evaporation and in the expansion of the sample vapour.     

Determination of aluminium and chromium in serum by atomic absorption spectrometry

Summary The optimal conditions for the determination of aluminium and chromium in blood serum are proposed. Several sample pretreatment procedures for the purpose are compared. The best results are obtained by sample dilution with nitric acid (0.1 mol/l) and addition of Mg(NO₃)₂ as modifier with a magnesium concentration of 0.2 mg/ml. This procedure has been used for studying the intestinal intake of aluminium by patients after oral administration of aluminium compounds.     

Semipreparative isolation of dehydrodiferulic and dehydrotriferulic acids as standard substances from maize bran

A method for the isolation of diferulic and triferulic acids in quantities and purity that comply with the requirements for their use as standard substances was developed. The procedure includes alkaline hydrolysis of destarched maize bran and ether extraction of liberated phenolic compounds. Following a first purification by liquid-liquid extraction Sephadex LH-20 chromatography is performed. This step is the core of the method and allows the separation of monomeric and dimeric/trimeric substances. A good pre-separation of di- and triferulic acids (purity in most cases >75%) is also achieved. Further separation and purification is carried out by semipreparative RP18-HPLC. Using this rapid, easy to handle, and moderately priced separation procedure it is possible to obtain approx. 41 mg 8-O-4'-diferulic acid, 27 mg 5-5'-diferulic acid, 12 mg 8-5'-diferulic acid (benzofuran form), 16 mg 8-5'-diferulic acid (open form), 11 mg 8-5'-diferulic acid (decarboxylated form), 7 mg 8-8'-diferulic acid (cyclic form), 5 mg 8-8'-diferulic acid (open form), and 10 mg 5-5',8'-O-4"-triferulic acid out of 20 g destarched maize bran. The incorporation of minor modifications allows a further upscaling of this procedure.     

Slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry for the direct determination of metal impurities in aluminium oxide ceramic powders

A new analytical procedure for the direct determination of metal impurities (Cr, Cu, Fe and V) in aluminium oxide ceramic powders by slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-AES) is reported. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of impurity elements in aluminium oxide ceramic powders from the graphite tube. A vaporization stage with a long ramp time and a short hold time provided the possibility of temporal analyte-matrix separation. The experimental results indicated that a 10 microL 1% m/v slurry of aluminium oxide could be destroyed and vaporized completely with 600 micrograms PTFE under the selected conditions. Two aluminium oxide ceramic powder samples were used without any additional pretreatment. Analytical results obtained by using standard addition method with aqueous standard solution were checked by comparison of the results with pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition and analyte-matrix separation. The limits of detection (LODs) between 0.30 microgram g-1 (Fe) and 0.08 microgram g-1 (Cu) were achieved, and, the repeatability of measurements was mainly better than 10%.     

Removal and recovery of chromium and chromium speciation with MINTEQA2

Chromium(III) is commonly found in large quantities in tannery wastewaters. For this reason, the recovery of the chromium content of these wastewaters is necessary for environmental protection and economic reasons. Removal and recovery of chromium were carried out by using ion exchange resins. To this purpose, two weakly acidic exchange resins Amberlite IRC 76 and Amberlite IRC 718 and a strongly acidic exchange resin Amberlite IR 120 were used. Basic chromium sulphate [Cr(4)(SO(4))(5)(OH)(2)] solutions in different concentrations and pH were used in all experiments as tanning baths. The resins were prepared in two different ionic forms as Na(+) and H(+). The effects of concentration, pH, stirring time and resin amount were investigated. The concentration range varied between 5 and 100 mg l(-1), pH range was between 1 and 8, stirring time between 5 and 60, and resin amount was between 50 and 1000 mg. Stirring speed was 2000 rpm during all these experiments. Exchange capacities, moisture contents and optimum conditions of these resins were determined in batch system. The results obtained showed that Amberlite IRC 76 and 718 weakly acidic resins had shown better performance than Amberlite IR 120 strongly acidic resin for removal and recovery of chromium(III) in Na(+) form. Optimum conditions were found as concentration 10 mg l(-1), pH 5, stirring time 20 min, and resin amount 250 mg. Furthermore, chromium(III) speciation was investigated for optimum concentration and pH with MINTEQA2 computer programme. The studied pH range was between 1 and 8 and concentration range was between 5 and 100 mg l(-1). Cr(OH)(2+) species were found to be dominant at pH 5 and 10 mg l(-1) concentration in batch studies. There was a correlation between experimental and computerised results.     

The quality of our drinking water: aluminium determination with an acoustic wave sensor

A new methodology based on an inexpensive aluminium acoustic wave sensor is presented. Although the aluminium sensor has already been reported, and the composition of the selective membrane is known, the low detection limits required for the analysis of drinking water, demanded the inclusion of a preconcentration stage, as well as an optimization of the sensor. The necessary coating amount was established, as well as the best preconcentration protocol, in terms of oxidation of organic matter and aluminium elution from the Chelex-100. The methodology developed with the acoustic wave sensor allowed aluminium quantitation above 0.07 mg L(-1). Several water samples from Portugal were analysed using the acoustic wave sensor, as well as by UV-vis spectrophotometry. Results obtained with both methodologies were not statistically different (alpha=0.05), both in terms of accuracy and precision. This new methodology proved to be adequate for aluminium quantitation in drinking water and showed to be faster and less reagent consuming than the UV spectrophotometric methodology.     

Enzymatic reactions on thin-layer chromatographic plates. II. Phospholipase A2 hydrolysis of phosphatidylcholine and separation of the products on a single plate

A procedure for the phospholipase A2 hydrolysis of phosphatidylcholine on a thin-layer chromatographic plate and subsequent separation of the products on the same plate is described. A 0.2-0.8-mg amount of Russell's viper venom (phospholipase A2) in 0.2 ml of 0.005 M calcium chloride solution was applied on a 0.5-mm silica gel G plate as a band over which 2-5 mg of egg phosphatidylcholine in 0.2 ml of diethyl ether containing 5% of methanol was evenly applied. After the reaction had proceeded for 15-20 min in a diethyl ether-saturated chamber at 25 degrees, the plate was developed with chloroform-methanol-water (65:25:4). The bands were identified and their contents extracted. The extent of hydrolysis under different reaction conditions was evaluated from the amount of lysophosphatidylcholine formed. Approximately 74.6% (maximum) conversion was obtained within 15 min at 25 degrees using a substrate to enzyme ratio of 4:1. The acyl group distributions in the 1- and 2-positions of hen egg phosphatidylcholine obtained from the gas-liquid chromatographic analysis of the methyl ester corresponding to the lyso and free fatty acid band agreed with those obtained by the method of Wells and Hanahan. The method is also applicable to phosphatidylethanolamine.     

The microchemical analysis of ferrous and non-ferrous alloys

Satisfactory methods are described for the determination of certain of the alloying constituents in small quantities of steels, aluminium alloys and white metals. In steels, lead is determined by using an extraction procedure with dithizone, whereas the stable colour produced by vanadium with 3 : 3' dimethylnaphthidine is used for determining this element. In aluminium alloys, absorptiometric procedures are recommended for determining copper, nickel, iron and manganese. The determination of silicon is advocated by the absorptiometric technique. For the determination of antimony, in white metals, a micro volumetric procedure with standard potassium bromate is recommended using α-naphthaflavone as indicator.     

ETAAS determination of aluminium and copper in dialysis concentrates after microcolumn chelating ion-exchange preconcentration

A procedure was developed for the preconcentration and determination of aluminium and copper in dialysis concentrates at the ng cm^–3 level. The preconcentration was achieved on microcolumns filled with Chelex-100 resin adjusted to a pH of 4.0. Five repetitive cycles of the sample through the column ensured a sufficient contact time for quantitative retention of aluminium and copper ions. The retained ions were eluted with HNO₃ (0.5 mol dm^–3). Aluminium and copper were determined in the eluate by Zeeman ETAAS using the standard addition technique. The procedure was performed under clean room conditions (class 10,000), The reliability of the results was evaluated by recovery tests, using dialysis concentrates spiked with aluminium and copper. The recoveries obtained ranged from 86 to 106% for aluminium and from 92 to 97% for copper. Using the recommended procedure, the LOD of aluminium and copper in dialysis concentrates (preconcentration factor 2) was found to be 0.5 ng cm^–3 and 0.2 ng cm^–3, respectively. Received: 19 December 1997 / Revised: 10 March 1998 / Accepted: 28 March 1998     

ETAAS determination of aluminium and copper in dialysis concentrates after microcolumn chelating ion-exchange preconcentration

A procedure was developed for the preconcentration and determination of aluminium and copper in dialysis concentrates at the ng cm^–3 level. The preconcentration was achieved on microcolumns filled with Chelex-100 resin adjusted to a pH of 4.0. Five repetitive cycles of the sample through the column ensured a sufficient contact time for quantitative retention of aluminium and copper ions. The retained ions were eluted with HNO₃ (0.5 mol dm^–3). Aluminium and copper were determined in the eluate by Zeeman ETAAS using the standard addition technique. The procedure was performed under clean room conditions (class 10,000), The reliability of the results was evaluated by recovery tests, using dialysis concentrates spiked with aluminium and copper. The recoveries obtained ranged from 86 to 106% for aluminium and from 92 to 97% for copper. Using the recommended procedure, the LOD of aluminium and copper in dialysis concentrates (preconcentration factor 2) was found to be 0.5 ng cm^–3 and 0.2 ng cm^–3, respectively. Received: 19 December 1997 / Revised: 10 March 1998 / Accepted: 28 March 1998     

Simultaneous determination of lead, nickel, tin and copper in aluminium-base alloys using slurry sampling by electrical discharge and multielement ETAAS

The simultaneous multielement determination of Pb, Sn, Ni and Cu in aluminium alloys by electrothermal atomic absorption spectrometry (ETAAS) was performed by a quick method using slurry sampling. The metallic colloidal slurries were obtained by an electrical discharge operated in liquid medium. In this work, the effects of aluminium were evaluated and the results show that it causes a strong retention of Pb, Ni and Cu at low pyrolysis temperatures which is overcome by employing high pyrolysis temperatures. Aluminium also significantly improves the thermal stabilisation of Pb and Sn, it being possible to reach pyrolysis temperatures of 1100 and 1300 °C, respectively. Such stabilisation indicates that the performance of aluminium as a matrix modifier for Pb is better than that obtained using phosphate and magnesium nitrate without substantial changes of the figures of merit. The effects of aluminium on the atomisation characteristics of the elements and those coming from the simultaneous multielement determination on the figures of merit of the elements are also discussed. In this work, a calibration procedure involving a matrix matching method with aqueous aluminium standards is proposed as a simple and efficient way to solve the inconveniences originated by the aluminium matrix. The proposed method was applied to the simultaneous multielement determination of several aluminium-base alloy standards giving results well within the recommended values.     

High performance liquid chromatographic determination of aluminium in natural waters in the form of its lumogallion chelate

A high performance liquid chromatographic method for the determination of ultra trace amount of aluminium in natural waters has been developed using lumogallion as a precolumn reagent for fluorimetric detection. The highly fluorescent Al-lumogallion chelate (lambda(ex) 500 nm, lambda(em) 574 nm) was separated on a LiChrosorb RP 18 column with an eluent containing 3:7 acetonitrile/0.02M potassium hydrogen phthalate buffer (pH 4.7) containing 10(-5)M lumogallion. The proposed system provides a simple, quick, selective and sensitive method for the determination of ultra-trace amount of aluminium in water samples. The detection limit defined as three times the standard deviation of the blank signal, was 0.05 mug/l. in water samples for 100 mul injection. The tolerance limits were 5 mg/l. for Fe(III) and F(-) and over 10 mg/l. for other foreign ions. The sensitivity of the method was independent of salinity. This method had been used for the direct determination of aluminium in both tap and coastal sea-waters without any preconcentration steps.     

An improvement on wright's method for the micro-determination of molecular Weights

An improvement of WRIGHT'S method for the determination of molecular weights is described, in which the filterpapers, carrying the solutions, are handled and weighed in light aluminium rings, and equilibrium is reached inside a closely fitting aluminium box. There is a wide choice of appropriate solvents with boiling points ranging from 100–184°. The accuracy reached is 5–10%. The amount of substance required is about 1 mg.     

Determination of aluminium and manganese in human scalp hair by electrothermal atomic absorption spectrometry using slurry sampling

Methods for the determination of aluminium and manganese in human scalp hair samples by electrothermal atomic absorption spectrometry using the slurry sampling technique were developed. Palladium and magnesium nitrate were used as chemical modifiers. Hair samples were pulverized using a zirconia vibrational mill ball, and were prepared as aqueous slurries. Determinations can be performed in the linear ranges of 1.9–150 μg l⁻¹ Al³⁺ and 0.03–10.0 μg l⁻¹ Mn²⁺. Limits of detection of 0.9 mg kg⁻¹ and 27.6 μg kg⁻¹ were obtained for aluminium and manganese, respectively. The analytical recoveries were between 99.6 and 101.8% for aluminium and in the 98.3–101.3% range for manganese. The repeatability of the methods (n=11), slurry preparation procedure and ETAAS measurement, was 16.0 and 7.9% for aluminium and manganese, respectively. The methods were finally applied to the aluminium and manganese determination in 25 scalp hair samples from healthy adults. The levels for aluminium were between 8.21 and 74.08 mg kg⁻¹, while concentrations between 0.03 and 1.20 mg kg⁻¹ were found for manganese.     

Slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry for the direct determination of metal impurities in aluminium oxide ceramic powders

A new analytical procedure for the direct determination of metal impurities (Cr, Cu, Fe and V) in aluminium oxide ceramic powders by slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-AES) is reported. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of impurity elements in aluminium oxide ceramic powders from the graphite tube. A vaporization stage with a long ramp time and a short hold time provided the possibility of temporal analyte-matrix separation. The experimental results indicated that a 10 μL 1% m/v slurry of aluminium oxide could be destroyed and vaporized completely with 600 μg PTFE under the selected conditions. Two aluminium oxide ceramic powder samples were used without any additional pretreatment. Analytical results obtained by using standard addition method with aqueous standard solution were checked by comparison of the results with pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition and analyte-matrix separation. The limits of detection (LODs) between 0.30 μg g^–1 (Fe ) and 0.08 μg g^–1 (Cu) were achieved, and, the repeatability of measurements was mainly better than 10%. Received: 28 August 2000 / Revised: 1 November 2000 / Accepted: 12 November 2000     

Bestimmung der freien Säure in wäßrigen Uran(IV)-nitrat- und Uran(IV)-perchloratlösungen

Methods described in literature for the determination of free acid in solutions containing plutonium(IV), uranium(VI) and aluminium(III) were investigated for their applicability in the presence of uranium(IV). Most methods turned out to work in the presence of uranium(IV). The simplest procedure was the suppression of the uranium(IV) hydrolysis by complexation with excess of fluoride. No bias was observed in the presence of 0–30 mg of uranium(IV). A variance of 1.4% resulted from the determination of 0.4 millimole of acid in the presence of 26 mg of uranium(IV) and a variance of 0.26% was obtained when 2 millimoles of acid were determined in the presence of 130 mg of uranium(IV). Uranium(IV) from 30–260 mg in 250 ml caused a negative bias, which can be corrected for. — A concentration of potassium fluoride in the titration medium of 10 g/l turned out to be optimum. In 11/2 years more than 750 determinations were carried out with the same glass electrode and no destruction of the electrode was observed. The influence of uranium(VI), iron(III) and aluminium (III) on the determination of the free acid was also investigated.     

Evaluation of the solid sampling technique for the determination of aluminium in biological materials by atomic absorption and atomic emission spectrometry

Summary Results for the determination of aluminium in several biological materials by atomic absorption and atomic emission spectrometry using the solid sampling technique in connection with a constant temperature furnace are given. A comparison was made with a dissolution procedure and good agreement was generally obtained. With the solid sampling technique it was possible to calibrate against aqueous standards and to achieve a precision of better than 10% r.s.d. for NBS 1577a Bovine Liver and IAEA H-4 Animal Muscle, providing that the sample mass was greater than 1.3 mg and that the peak area was evaluated. Laboratory air and the solid sampling procedure were identified as possible sources of contamination.

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Auswertung der Feststofftechnik für die Bestimmung von Aluminium in biologischen Materialien durch AAS und AES

     

以无机铝盐为前驱体用溶胶凝胶法合成中孔氧化铝

以水合硝酸铝(Al(NO3)3·9H2O)为前驱体, 通过乙醇介质中环氧丙烷的开环反应促使形成了透明的块状氧化铝凝胶. 凝胶在常压下干燥并于700 ℃焙烧后得到中孔无定型氧化铝. 通过改变环氧丙烷的加入量实现了氧化铝孔径和孔体积等宏观结构性能的调节. 用扫描电镜(SEM)、傅立叶变换红外光谱(FI-IR)和差热分析(DTA)等方法对样品进行了表征. 由于合成中存在环氧丙烷开环产物作为液体模板剂的造孔作用, 在氧化铝凝胶中造成了孔分布曲线具有双峰分布的墨水瓶状孔. 反应过程中pH值的测定和红外光谱的表征结果都证明环氧丙烷是一种很好的质子消耗剂, 其开环促使铝离子水解聚合并形成凝胶网络结构. 同时根据表征结果对环氧丙烷参与的溶胶凝胶氧化铝的合成机理进行了探讨.     

Validation and evaluation of a high performance liquid chromatographic method for the determination of aluminium in wine

A new method is reported for the determination of aluminium in wine by HPLC, involving derivatisation with 8-hydroxyquinoline (oxine) in the presence of micelles resulting in the formation of a fluorescent derivative. The complex is separated on a C18 column using a mobile phase of oxine - SDS - 35% acetonitrile, in a pH 7 buffer. The method was validated in the range 0.125-2 mg/l in a synthetic wine. The method was applied to the determination of aluminium in white, rosé and red wines and results compared with those obtained by atomic absorption (GFAA). Aluminium concentrations found by HPLC in white wines were greater than those found in red wines. Further investigation using a polyphenol-enriched white wine revealed a statistically significant inverse relationship between wine polyphenol content and the aluminium concentration determined by HPLC. The method may therefore be envisaged for the determination of unbound aluminium in wine.