Mössbauer Study of El-Bahrain Meteorite

Procedures for the determination of traces of rare earth elements (REE) in geological samples by instrumental neutron activation analysis (INAA) and high resolution liquid chromatography (HPLC) are presented. The international standard reference materials AGV-1, GSP-1 and G-2 (USGS) were tested for the determination of REE concentrations using both techniques. The results obtained showed good agreement with certified values, giving relative errors less than 10%. By using INAA, the REE La, Ce, Nd, Sm, Eu, Tb, Yb and Lu were determined. All the REE, except Dy and Y, were determined when HPLC was employed. The application of INAA and HPLC to the determination of REE in geological samples is also discussed.     

Preconcentration of rare earths in geological materials with ascorbic acid for their neutron activation analysis

The potential use of ascorbic acid as a complexing reagent in the separation and preconcentration of rare earth elements (REE) in geological materials in a suitable solid matrix has been demonstrated. Traces of REE from some USGS standard rock samples, viz., GSP-1, G-2, AGV-1 and PCC-1, have been separated after acid dissolution in two ways: (1) by ion exchange chromatography on Dowex 50×8 column and Na-ascorbate as eluent and (2) by direct complexation with ascorbic acid under specific experimental conditions. The separated REE were coprecipitated with the non isotopic diluent, calcium fluoride, before neutron activation analysis. Radiometric determinations showed that the overall recovery of REE in both cases was practically quantitative.     

Determination of rare earth elements in Indian kimberlite using inductively coupled plasma mass spectrometer (ICP-MS)

A method has been developed for the analysis of rare earth elements (REEs) in kimberlite samples using inductively coupled plasma mass spectrometer (ICP-MS). The samples were dissolved using sodium peroxide fusion and after appropriate dilutions the solutions were analyzed using ICP-MS. The paper presents the concentration of rare-earth elements as determined by ICP-MS in eight kimberlite samples from Central India. The method was validated using certified reference materials STSD-1 and STSD-2 from Canadian Certified Reference Material Project. The method detection limit of various REEs varies from 0.12 to 1.54?mg?kg^?1. The total REE concentrations range from 418 to 726?mg?kg^?1 and fall within the interval of those reported in the literature for kimberlites. Despite the marked difference in the REE contents, all the analyzed samples show similar REE patterns that resemble those for kimberlites. In order to compare ICP-MS results, the samples were analyzed using instrumental neutron activation analysis which is a reference method for determination of REEs in geological samples.     

Determination of the enantiomeric purity of amphetamine after derivatization with Sanger’s reagent (2,4-dinitrofluorobenzene [DNFB]) by simultaneous dual circular dichroism and ultraviolet spectroscopy

Determination of Se in biological materials was attempted by microwave-induced plasma mass spectrometry (MIP-MS). (1) Serum samples were available after 10 times dilution with 0.5% nitric acid solution containing 0.1% Triton X-100. When oxygen gas was inserted into the plasma gas (nitrogen) in order to improve the combustion, the sensitivity was reduced to 45%. The detection limit of this method was 0.5 ng/mL. (2) Standard reference materials on commercial base were used to evaluate the accuracy of the Se determination by MIP-MS after microwave digestion. In samples like bovine liver and human hair with Se concentrations of more than 0.7 μg/g, the standard curve method after internal standard (IS) correction was acceptable. This procedure was unsuitable for samples with low Se concentrations such as milk powder (certified value of Se 0.11 μg/g), or plant leaf samples. (3) Instead of IS correction, the peak height of the spectrum was used for calculations from the matrix matched calibration curve. The results of all materials were close to the certified values, even at 25 ng/g. The detection limit of the MIP-MS with microwave digestion and IS correction was 0.05 ng/mL in standard solutions. The detection limit of the peak height method was 0.1 ng/mL and was estimated to be < 20 ng/g in plant materials.     

Determination of tin, bismuth, antimony, indium, gallium and arsenic by solvent extraction cum atomic absorption spectrophotometry

A rapid atomic absorption spectrometric method for the determination of tin, antimony, bismuth, indium, gallium and arsenic in geological materials, steels and alloys is described. The samples are fused with sodium peroxide (for geological samples such as cassiterite and sulphides) or decomposed with sulphuric/hydrochloric acid mixture or by alkaline fusion (for silicates or bauxites) or by acid treatment (for steels, alloys and certain geological samples). The elements of interest are extracted as their iodides into methyl isobutyl ketone, stripped into aqueous solution by treatment with benzene, concentrated nitric acid and water, and determined by flame atomic-absorption spectrometry. Detailed study is made on stripping of the metals from organic phase as there no simple and rapid stripping procedures available. The method allows the determination of Sn, Sb, Bi and In down to 2 ppm and Ga down to 5 ppm. The relative standard deviations range up to 10% with an average of 2.5%. Apparent recoveries of these metals range from 90 to 110 with an average of 95% for Sb and 99% for others.     

Improved capillary electrophoresis method for measuring rare-earth elements in synthetic geochemical standards

An improved capillary electrophoresis (CE) method for quantifying rare-earth elements (REEs) in synthetic geochemical standards was developed. Synthetic standard solutions were obtained from high purity metal oxides. The separation of REE total group (lanthanum to lutetium) was defined as a primary objective. Special attention was also focused on the optimized separation of europium (Eu) and gadolinium (Gd) because in earlier applications they presented overlapping problems. Their separation and quantitative determinations are essential for geological applications. For the rapid separation of REEs in synthetic geochemical standards, the temperature of the separation device was optimized. An analysis temperature of 15 degrees C enabled both the rapid separation of REEs within 2 min and the overlapping problem of Eu-Gd to be resolved. The detection limits (<0.1 ng) and precision estimates (generally better than 5%) were found to be satisfactory for most geological applications.     

Determination of the enantiomeric purity of amphetamine after derivatization with Sanger’s reagent (2,4-dinitrofluorobenzene [DNFB]) by simultaneous dual circular dichroism and ultraviolet spectroscopy

Determination of Se in biological materials was attempted by microwave-induced plasma mass spectrometry (MIP-MS). (1) Serum samples were available after 10 times dilution with 0.5% nitric acid solution containing 0.1% Triton X-100. When oxygen gas was inserted into the plasma gas (nitrogen) in order to improve the combustion, the sensitivity was reduced to 45%. The detection limit of this method was 0.5 ng/mL. (2) Standard reference materials on commercial base were used to evaluate the accuracy of the Se determination by MIP-MS after microwave digestion. In samples like bovine liver and human hair with Se concentrations of more than 0.7 μg/g, the standard curve method after internal standard (IS) correction was acceptable. This procedure was unsuitable for samples with low Se concentrations such as milk powder (certified value of Se 0.11 μg/g), or plant leaf samples. (3) Instead of IS correction, the peak height of the spectrum was used for calculations from the matrix matched calibration curve. The results of all materials were close to the certified values, even at 25 ng/g. The detection limit of the MIP-MS with microwave digestion and IS correction was 0.05 ng/mL in standard solutions. The detection limit of the peak height method was 0.1 ng/mL and was estimated to be < 20 ng/g in plant materials. Received: 25 September 1998 / Revised: 15 February 1999 / Accepted: 18 February 1999     

Inductively coupled plasma-atomic emission spectrometric determination of rare earth elements in geological materials

Inductively coupled plasma-atomic emission spectrometry (ICP-AES) has been applied to the determination of the rare earth elements (REE) lanthanum to lutetium (except terbium) in a range of geological materials. Group separation of the REE is carried out by sintering the sample with sodium peroxide to remove the bulk of the matrix, followed by fluoride precipitation with an yttrium carrier. This minimizes spectral interferences and provides sensitivities that are adequate for concentration levels around crustal abundances. The precision (2σ) is 3–5% for most of the elements and about 10% for some of the less abundant elements with concentrations that approach the limit of determination. Comparison of results obtained on a range of reference samples with literature values demonstrates the suitability of the procedures to provide rare earth abundance data for geochemical investigations.     

Separation and preconcentration of the rare-earth elements and yttrium from geological materials by ion-exchange and sequential acid elution

The abundance of rare-earth elements (REE) and yttrium in geological materials is generally low, and most samples contain elements that interfere in the determination of the REE and Y, so a separation and/or preconcentration step is often necessary. This is often achieved by ion-exchange chromatography with either nitric or hydrochloric acid. It is advantageous, however, to use both acids sequentially. The final solution thus obtained contains only the REE and Y, with minor amounts of Al, Ba, Ca, Sc, Sr and Ti. Elements that potentially interfere, such as Be, Co, Cr, Fe, Mn, Th, U, V and Zr, are virtually eliminated. Inductively-coupled argon plasma atomic-emission spectroscopy can then be used for a final precise and accurate measurement. The method can also be used with other instrumental methods of analysis.     

Determination of rare earth elements in environmental matrices by sector-field inductively coupled plasma mass spectrometry

In the framework of an international certification campaign, sector-field inductively coupled plasma mass spectrometry (sector-field ICP-MS) was used for the accurate determination of the rare earth elements in five candidate reference materials: aquatic plant, calcareous soil, mussel tissue, river sediment, and tuna muscle. All samples were taken into solution by use of microwave-assisted or mixed microwave-assisted / open beaker acid digestion. Subsequently, the samples were appropriately diluted and subjected to ICP-MS analysis. Except for Sc, all the elements involved were determined at low mass resolution (R = 300). For Sc, application of a higher resolution setting (R = 3,000) was required to separate the analyte signal from those of several molecular ions which gave rise to spectral overlap at low mass resolution. Some of the heavier REE can also suffer from spectral overlap attributed to the occurrence of oxide ions (MO+) of the lighter REE and Ba. This spectral overlap could be successfully overcome by mathematical correction. Matrix effects were overcome by use of two carefully selected internal standards, such that external calibration could be used. On each occasion, a geological reference material was analyzed as a quality-control sample and the reliability of all results obtained was additionally checked by means of chondrite normalization. For tuna muscle the content of all REE was below the limit of detection. For calcareous soil and river sediment, low to sub microg g(-1) values were observed, whereas the REE content of aquatic plant and mussel tissue was considerably lower (low to sub ng g(-1)). Overall, the results obtained were in excellent agreement with the average values, calculated on the basis of all "accepted" values, obtained in different laboratories using different techniques.     

Determination of rare-earth elements by high-performance liquid chromatography/inductively-coupled plasma/atomic emission spectrometry

Liquid chromatography coupled on-line to a sequential ICP/AES system is applied for the determination of 14 rare-earth elements (REEs) in samples with widely different concentrations of REEs and matrix elements. The REEs are separated on a cation-exchanger by applying an α- hydroxyisobutyric acid gradient. The determination limits were the same as those obtained by continuous nebulization of single-element standard solutions. The chromatographic separation precludes mutual spectral interferences between the REEs. The practical value of the method developed is demonstrated by the determination of REE impurities in Specpure rare-earth oxides, by its demonstrated potential to evaluate real spectral interferences, and by the analysis of geological samples (natural phosphates) with relatively low total REE contents. The detection limits of REEs in these natural phosphates ranged between 0.005 and 0.4 μg g^?1.     

一体化碰撞反应 (iCRC)-电感耦合等离子体质谱法测定地质样品中痕量稀土元素

钡以及轻稀土元素氧化物对中、重稀土元素的干扰一直是质谱测试中存在的问题。建立了石墨粉垫底碳酸钠-硼酸混合熔剂熔融前处理样品,以_¹⁰³Rh为内标校正,一体化碰撞反应-电感耦合等离子体质谱仪法测定地质样品中稀土元素含量的方法。探讨了碳酸钠-硼酸混合熔剂熔融前处理样品注意事项、碰撞模式下碰撞气流量和离子透镜的参数的优化、干扰校正试验等问题,采用国家标准物质GBW07403、GBW07405、GBW07427、GBW07429验证,实验结果表明,各元素线性关系良好,相关系数均大于0.999,方法检出限在0.01～0.03mg/kg之间,相对误差为0.13%～7.1%,相对标准偏差为0.79%～6.59%,测试结果与标准值相吻合。对实际样品分析,得到平滑的球粒陨石归一化的稀土元素配分曲线,证明测定结果是合理可信的。该方法熔剂用量少,过程空白低,对器皿的侵蚀小,直接加热浸取,简化了操作过程,适用于大批量地质样品中稀土元素的测定。     

岩石样品中43种元素的高分辨等离子质谱测定

以ＨＮＯ３和ＨＦ高压密封溶样,选择各元素浓度分布高低兼顾的国标ＷＢＧ０７１０３和ＷＢＧ０７１０５作参考标准,以高分辨ＩＣＰ－ＭＳ仪器测定岩石样品中４０余种元素,方法检出限在０．１～１８８ｎｇ／ｇ之间,各元素相对标准偏差（ＲＳＤ,ｎ＝６）多在５％以下,方法已用于批缇岩石样品分析。     

Neutron activation analysis of the rare earth elements in rocks from the earth's upper mantle and deep crust

Three techniques for analyzing rare earth elements (REE) in geological materials are described, i.e. instrumental neutron activation analysis (INAA), neutron activation analysis with pre-irradiation chemical REE separation (PCS-NAA) and radiochemical neutron activation analysis (RNAA). The knowledge of REE concentrations in eclogites, peridotites and minerals from the earth's lower crust and upper mantle is very useful in constraining their petrogenetic history.     

Coupling of solvent semimicroextraction with capillary electrophoresis using ethyl acetate as sample matrix

This paper reports a strategy to couple liquid-liquid semimicroextraction (LLsME) with capillary electrophoresis (CE) based on a newly introduced on-column decomposable sample matrix, ethyl acetate (EA). LLsME was performed in volumetric flasks of 100 mL. Samples containing an aqueous phase were first saturated with EA. Then, an extra 500 microL of EA was added to extract the samples. Sample injection in CE could be made in hydrodynamic mode by dipping the injection end of the capillary into the organic (EA) phase in the volumetric flasks. As a demonstration, alkylphenones in water samples were extracted by LLsME into EA and subjected to separation by micellar electrokinetic chromatography (MEKC). Alkylphenones of C8-C12 with concentrations of about 10 ppb can be concentrated and detected after extraction; extraction efficiencies range from 72- to 334-fold. Linearity of extraction was determined and the effect on reproducibility by spiking an internal standard was studied. The method developed is time-saving and requires no further special experimental device other than a basic CE setup. Therefore, it would be readily acceptable for routine analysis, especially in analytical laboratories dealing with environmental samples.     

Separation of yttrium and rare earth elements from geological materials

The isolation of rare earth elements (REE) from geological materials by ionexchange chromatography with Dowex 50W-X8 is described. Elution curves for Y, La, Ce, Nd, Sm, Eu, Gd and Yb are determined by inductively-coupled plasma emission spectrometry. Separation from the main constituents including aluminium is accomplished by elution with 0.8 M, 4 M and 6 M hydrochloric acid. Recoveries of the individual REE are 90–100%. The method was confirmed by tests on synthetic basalt, andesite and dacite.     

Spectrophotometric determination of rare earth elements by flow injection analysis based on their reaction with xylenol orange and cetylpyridinium bromide

Individual rare earth elements (REE) and their mixtures were determined by a FIA method based on the reaction with Xylenol Orange (XO) in the presence of cetylpyridinium bromide (CPB). Volumes of 30 microl of 2.5-25 microM REE solutions were injected into a carrier stream of 0.1M acetate buffer of pH 4.5 or 5.5 that was 0.06 mM in XO and 0.6 mM in CPB. At 1.8 ml/min flow rate, a sampling frequency of up to 100 samples per hour was achieved. The detection limits were in the range of 0.1-0.4 microg/ml REE and relative standard deviation of the measurement was 0.88% rel.     

Development of a liquid chromatography/tandem mass spectrometry assay for the quantification of rabeprazole in human plasma

A simple and sensitive liquid chromatography/tandem mass spectrometry method, employing electrospray ionization, has been developed and validated to quantify rabeprazole in human plasma using omeprazole as the internal standard. The method was validated to demonstrate the specificity, lower limit of quantification, accuracy, and precision of measurements. Selected reaction monitoring was specific for rabeprazole and omeprazole (the internal standard, IS); no endogenous materials interfered with the analysis of rabeprazole and IS from blank plasma. The assay was linear over the concentration range 0.2-200 ng/mL using a 2 microL aliquot of plasma. The correlation coefficients for the calibration curves ranged from 0.9988-0.9994. The intra- and inter-day precision, calculated from quality control samples, were less than 6.65%. A mixture of methanol and water (50:50) was used as the isocratic mobile phase, with 0.1% of formic acid in water, that did not affect the stability of rabeprazole or IS. A simple sample preparation method of protein precipitation with methanol was chosen. The method was employed in a pharmacokinetic study after oral administration of 20 mg rabeprazole to 24 healthy volunteers.     

Determination of rare-earth elements and yttrium in silicate rocks by sequential inductively-coupled plasma emission spectrometry

An ICP—AES method for determination of rare-earth elements (REE) and yttrium at trace levels in silicate rocks is described. The method involves decomposition of the rock sample by heating with a mixture of hydrofluoric and perchloric acid, followed by precipitation of the REE and Y as oxalates, with calcium as carrier. The oxalate precipitate is ignited to the oxide, which is then dissolved in dilute nitric acid and the solution is used for ICP—AES measurements, with use of pure REE solutions as calibration standards. The method has been applied to the determination of REE in a number of standard reference materials and the results have been compared with the reported values. Three other silicate rock samples have also been analysed for REE and Y by this method.     

Cation-exchange isolation and ICP-AES determination of rare earth elements in geological silicate materials

An ion-exchange ICP-AES method for the determination of 14 rare earth elements (REEs) and Y in geological materials is described. The separation of REEs from Ba using a Dowex 50W-X8 cation resin is especially considered since Ba is an excellent internal standard for REE determination by this technique. Although total recovery with either HCl or HNO₃ may be achieved, it is advantageous to use both acids sequentially. Volume and concentration of the acids are optimized attaining a quantitative separation of REEs from Ba by the introduction of the sample solution in a 1.75 mol/l HCl medium, followed by elution with 2 mol/l HNO₃ to remove matrix elements and with 7 mol/l HNO₃ to elute the analytes. The total elution volume is significantly reduced without decreasing the efficiency. The behaviour of the matrix constituents under the selected conditions is also studied, evaluating their elution percentages in each step. The final solution obtained contains only the REEs and Y, with the bulk of Sc and minor amounts of Cr, Fe, Hf and Ta. Experimental data for 5 geological reference standards (NIM-G, GSP-1, AGV-1, NIM-L and NIM-S) are reported. Good agreement between the present results and previously accepted values by various analytical techniques is observed.