Determination of tungsten by calcium atomization inhibition titration

A method for the determination of tungsten utilizing inhibition effect on calcium emission in hydrogen-air flame is described. The technique is based on atomization inhibition titration (AIT) and subsequent release by means of lanthanum. The signal enhancement following the lanthanum addition is proportional to the tungsten concentration up to 0.8 ppm W. A detection limit of 0.013 ppm and a determination limit of 0.12 ppm were found. The effect of 13 foreign ions on the tungsten determination was investigated.     

Elimination of phosphate interference in flame photometric determination of strontium and barium

The interference of phosphate in the flame emission of calcium, strontium and barium was studied. The emission intensity decreases proportionally to the amount of interfering anion up to a maximum depression for equimolar amounts of phosphate to metal. A thermostable phosphate is formed before the cation enters the flame. Appropriate addition of lanthanum restores the three alkaline earth lines to their intensities in absence of phosphate, the lanthanum displacing, the alkaline earths from their phosphates before the hot region of the flame is reached.     

Determination of calcium, magnesium and strontium in soils by flow injection flame atomic absorption spectrometry

Several procedures for the determination of Ca, Mg and Sr in soils have been compared on the basis of the accuracy of analysis of two NIST reference materials (Montana Soils SRM 2710 and SRM 2711). Samples were dissolved in a mixture of hydrofluoric and nitric acids in sealed vessels in a microwave oven and in teflon beakers on a hot plate. The digests obtained from both dissolution methods were evaporated to dryness in an attempt to remove silicon. Boric acid was added to prevent the precipitation of the lanthanum releasing agent (as lanthanum fluoride) and potassium was added as an ionization buffer. Determinations were made by flame atomic absorption spectrometry with both the nitrous oxide-acetylene flame and the air-acetylene flame, with calibration either by standard additions or against external standards matrix matched with respect to nitric acid, boric acid, lanthanum and potassium. The silicon remaining in the solution was also determined by external calibration. A single-line flow injection manifold was used to overcome any problems due to the presence of high dissolved solids. A volume of 300 mul was injected into a water carrier stream flowing at 8 ml min(-1). To determine Ca in the air-acetylene flame, it was necessary to remove silicon. Magnesium was determined in either flame without complete removal of the silicon, however, for the determination of Sr, it was necessary to remove the silicon and use the nitrous oxide-acetylene flame. The indicative value for Sr in SRM 2710 was too low: the value determined was 360+/-30 mug g(-1).     

Direct FIA-AS determination of potassium and magnesium in cement samples by use of the slurries approach

A direct procedure has been developed for the flame atomic determination of potassium and magnesium in cement samples. A 50-mg sample is dispersed in 25 ml of 0.13M nitric acid; 100 mul of this slurry is injected in a double channel FIA manifold simultaneously with 100 mul of a 10% (w/v) lanthanum solution. This procedure allows the rapid extraction of potassium and magnesium by leaching of the sample; nitric acid is not necessary if only potassium must be determined and the sample can be diluted with only distilled water. Aqueous standards are used. The manifold employed includes a well-stirred mixing chamber, which provides an adequate on-line dilution of the sample, in order to obtain emission or absorbance measurements in the dynamic range of the elements to be determined. The results obtained in the analysis of real samples agree with those found by flame atomic spectrometry after a previous alkaline fusion with lithium carbonate, and exhibit better precision. The limit of detection of the procedure is 0.007% for K(2)O and 0.01% for MgO and the precision of the entire procedure corresponds to a relative standard deviation of 1%.     

Suppression of interferences in the determination of lead in natural and drinking waters by graphite-furnace atomic absorption spectrometry

The problem of matrix interference encountered in the determination of lead in natural and drinking waters by graphite furnace atomic absorption spectrometry is examined by looking at the individual effects of various constituent salts (NaCl, KCl, MgCl₂ and CaCl₂, Na₂SO₄, KH₂PO₄ and Mg(NO₃)₂), of which MgCl₂ and Na₂SO₄ interfered most severely. The use of the L'vov platform decreased the sulphate interference, but was not successful in removing the other interferences. The mixture of 0.05% (w/v) lanthanum (as LaCl₃) and 1% (v/v) nitric acid previously proposed for wall atomisation was found to be effective in controlling the interferences. Nitric acid alone removed almost completely the effects of MgCl₂ and CaCl₂, but had little effect on the interference of sulphate, which required the addition of lanthanum for suppression. The removal of interferences in real water samples by the lanthanum/nitric acid mixture is demonstrated by comparison of results obtained by this approach with those obtained by atomic fluorescence spectrometry and by flame atomic absorption spectrometry after preconcentration by evaporation.     

Use of lanthanum and sulphuric acid to suppress interferences in the flame photometric determination of calcium m soil extracts

Interference by iron, aluminium and phosphate in the flame photometric determination of calcium in soil extracts is not fully suppressed by lanthanum unless dilute sulphuric acid is also present. The investigation was restricted to the oxy-acetylene flame.     

Ruthenium determination in synthetic purex waste solutions by AAS

A method for the determination of ruthenium in synthetic Purex waste solutions by flame AAS is described. With the usual flames and a lanthanum buffer, only cerium interference in the air-acetylene flame need be considered under the conditions applied. Ruthenium nitrosyl nitrate, ruthenium(IV) hydroxychloride and alkaline ruthenate samples gave identical results, showing that the extraordinarily stable Ru-NO bond does not hinder atomization. The preparation and standardization of the ruthenium nitrosyl solutions, and the alkaline fusion, are briefly described.     

Determination of calcium, magnesium and zinc in unused lubricating oils by atomic absorption spectroscopy

Varying concentrations of lanthanum and strontium were added to solutions of ashed unused lubricating oils for the determination of calcium, magnesium and zinc content using flame atomic absorption spectrophotometry. At least 3000 μg g⁻¹ of lanthanum or strontium was required to completely overcome the interference of the phosphate ion, PO³⁻₄, and give peak values for calcium. The presence of lanthanum or strontium did not cause an appreciable increase in the amount of magnesium and zinc obtained from the analyses. The method is fast and reproducible, and the coefficients of variation calculated for the elements using one of the samples were 1.6% for calcium, 3.5% for magnesium and 0.2% for zinc. Results obtained by this method were better than those obtained by other methods for the same samples.     

电感耦合等离子体原子发射光谱法测定钼镧合金中镧元素

采用盐酸-硝酸溶解钼镧合金样品,建立电感耦合等离子体原子发射光谱法（ICP-AES）测定钼镧合金中镧元素的分析方法,给出影响测量结果的不确定度分量。选择379.478nm为镧的分析谱线,通过基体匹配法消除基体钼的干扰。在优化条件下对钼镧合金样品进行测定,线性相关系数在0.999以上,定量下限为0.048%,测定结果的相对标准偏差（RSD,n=11）小于3%,回收率为93.00%~105.00%。该方法快速、准确,可以满足实际生产中钼镧合金样品的测定要求。     

Atomic absorption spectrometric determination of calcium and other metallic elements in some animal protein sources

The phosphorus content of some animal protein sources was determined in order to identify the sample with the highest phosphorus content for use as a pilot sample. Varying concentrations of strontium and lanthanum were added to solutions of the ashed pilot sample for the determination of calcium and magnesium using flame atomic absorption spectrophotometry operated on the air-acetylene mode. At least 3000 ppm of strontium or lanthanum was required to completely overcome the interference of phosphate ion, PO(4)(3-), and give peak values for calcium. The presence of strontium or lanthanum did not affect the amount of magnesium obtained from the analyses. Based on this, a procedure is proposed and the results obtained by this procedure for calcium are more enhanced than those obtained without the addition of strontium or lanthanum for the same samples whereas comparable results were obtained for all other elements whether strontium or lanthanum was added or not. The method gives more accurate results and is reproducible. The coefficients of variation calculated using one of the samples were 0.58% for magnesium, 3.12% for zinc; 0.44% for calcium, 11.06% for lead, 22.22% for nickel, 3.53% for manganese and 3.50% for iron at the concentration levels found in that sample. Recoveries of spiked calcium, magnesium and zinc were quantitative. Also, for selected elements, results from the procedure compared well with those from chemical analysis.     

Interferences and Methods for Their Elimination in the Determination of Lanthanum as LaO by Laser-Enhanced Molecular Flame Ionization Spectrometry

Interfering effects of some elements on the determination of lanthanum as LaO in a natural gas–air flame by laser-enhanced molecular ionization spectrometry were studied. It was demonstrated that easily ionized elements (Li, K, Na, Mg) exert an ionization effect; in addition, sodium introduces spectral interference. Techniques were proposed for the elimination of these interfering effects.     

稀土元素对磷钼钒杂多酸催化氧化活性的影响

讨论了镧的置換度和稀土元素对含氧有机化合物在杂多酸催化剂上的氧化反应的影响,并与催化剂的结构进行了关联。镧的引入不影响氧化脱氢反应,而明显削弱插入氧反应。其它稀土元素的影响与镧相同。     

Continuous ultrasound-assisted extraction coupled to a flow injection-flame atomic absorption spectrometric system for calcium determination in seafood samples

Calcium was extracted on-line from solid seafood samples by a simple and rapid continuous ultrasound-assisted extraction system. This system is connected to a flow injection manifold, which allows the on-line flame atomic absorption spectrometric determination of calcium. This method enables the analysis of solid samples avoiding time-consuming traditional sample preparation methods and their inherent errors. The on-line manifold for calcium determination is the simplest possible, because a volume of 250 L of acid extract is injected into an ultrapure water carrier stream. The acid extract was diluted on-line with lanthanum, which also acts as masking agent in order to avoid chemical interferences. The continuous monitoring of the calcium signal was accomplished by flame atomic absorption spectrometry. A Plackett-Burman experimental design was used for the optimisation of the continuous leaching procedure. The method allowed a total sampling frequency of 40 samples per hour, with a relative standard deviation for the complete procedure of 0.9% (for a sample containing 3414.35 mg/kg calcium (dry mass)). The limit of detection was found to be 44.4 mg/kg (dry mass) for 5 mg of sample. The analytical procedure was applied to real seafood samples.     

微波等离子体炬原子发射光谱法测定铁增敏效应

针对在低功率下工作的微波等离子体炬原子发射光谱法(MPT-AES)存在对一些元素检测灵敏度较低和抗基体干扰能力弱的问题,以氩气为载气和工作气,研究了表面活性剂及镧盐对MPT-AES测定铁的增敏效应,考察了铁测定的工作条件和共存元素对铁测定的影响.实验结果表明,非离子表面活性剂对铁的测定有抑制作用,而阳离子表面活性剂和镧盐对铁的测定有增敏作用,其中镧盐增敏效果最好.以镧盐为增敏剂,不仅可提高MPT-AES测定铁的灵敏度,还可增加共存元素的允许量.当体系中镧浓度为0.500 mg/m L时,至少可使40倍的锌,30倍的钴,20倍的镍、锰,15倍的钙,10倍的镁、铜和钠不影响铁的测定.与不加镧时相比,铁的发射强度提高了2.4倍,检出限由原来的27.5×10~(-3)μg/m L下降为8.5×10~(-3)μg/m L.将本方法应用于原油样品中铁的测定,所得结果与火焰原子吸收光谱法测定结果一致.     

Direct determination of calcium, magnesium, sodium and potassium in water by flow injection flame atomic spectroscopy, using a dilution chamber

Summary A simple procedure to carry out the direct analysis of calcium, magnesium, sodium and potassium in water by flow injection analysis (FIA) using flame atomic absorption spectroscopy (AAS) or flame photometry (FP) has been developed, using a well stirred dilution chamber to extend the calibration range, and both a double injector and the merging zone technique to add a lanthanum solution to samples and standards. The results obtained in the analysis of real samples agree with those found by a batch flame atomic procedure. The use of the dilution chamber makes it possible to carry out the calibration using the dilution profile of a single concentrate standard for each element, and an empirical dilution equation, which could be employed for all the elements is determined in each work session.

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Direkte Bestimmung von Calcium, Magnesium, Natrium und Kalium in Wasser durch Fließinjektions-Flammen-Atomspektroskopie unter Verwendung einer Verdünnungskammer

     

A study of the flame emission characteristics of lanthanum in an aqueous-alcoholic medium

The determination of lanthanum by measuring its flame emission at several wave lengths has been evaluated by means of two recording spectrophotometers equipped with special photomultiplier detecting devices. In addition, a comparison of the effect of an aqueous and alcoholic medium was carried out. In general, the interference from foreign ions is least at the higher wave length of 743 mμ. In most cases, especially with transition elements, the interference is lessened when 1 : 1 water-methanol solution is used. The exceptions to this rule are titanium,thorium and zirconium which cause less interference in an aqueous solution. The method used in conjunction with a standard addition technique, has been applied to the determination of lanthanum in solutions of thorium oxide, uranium, glass, and didymium oxide mixtures.     

The use of lanthanum chloride to prevent interferences in the flame photometric determination of exchangeable calcium in soils

An examination of the interferences of aluminium, bicarbonate, phosphate, sulphate and silicate in the flame photometric determination of calcium in ammonium chloride solutions has shown that, with the exception of bicarbonate, all cause serious interference. Addition of lanthanum to the solution can satisfactorily prevent each of these interferences Provided the lanthanum to aluminium ratio is at least 12.5 I by weight all interference from aluminium can be prevented The use of lanthanum chloride to prevent such interferences in the determination of calcium in ammonium chloride lcachates of soils is discussed and a simple flame photometric method for the determination of exchangeable calcium in soils is proposed.     

Determination of Cadmium and Lead in Sea Water after Extraction Using Electrothermal Atomisation. Minimisation of Interferences from Co-Extracted Sea Salts

Abstract

Interferences from small amounts of sea salt in the determination of cadmium and lead were investigated. Test samples were made to mimic solutions obtained after extraction of sea water for trace metal analysis. Sea salt concentrations in the range 0–400 mg/l were investigated. Background absorption from this salt was high but easily minimised through the addition of nitric acid (2 % v/v). Sensitivity reductions due to the salt were considerable and varied from one graphite tube to the other. This problem was overcome by the addition of 1000 mg lanthanum per litre of sample. The positive effect of the lanthanum matrix modification is thought to be due to a change of the graphite tube surface.     

Determination of calcium in cement by flame-emission spectrometry with strontium as internal standard

A combination of strontium as internal standard and lanthanum as releasing agent is recommended for direct flame-emission spectroscopic determination of calcium in cement, an air-acetylene flame being used.     

Determination of indium in aluminium alloys by flame atomic-absorption spectroscopy and flame atomic-emission spectrometry

The use of flame atomic-absorption and atomic-emission spectrometry for the determination of indium in aluminium alloys is described. Two types of flame are used: air—acetylene and nitrous oxide—acetylene. The efrect of other ions, especially aluminium, has been studied, and the use of lanthanum as a releasing agent is proposed for both techniques, the amount used depending on the amount of aluminium present.