Determination of trace siderophile elements in rock and meteorite samples by radiochemical neutron activation analysis

A simple and effective radiochemical procedure for radiochemical neutron activation analysis (RNAA) of ultra-trace siderophile elements (Ru, Re, Os and Ir) and rare earth elements (REEs) in rock and meteorite samples is presented. To design the procedure, several separation schemes of siderophile elements were examined by using radioactive tracers. By applying the procedure to rock and meteorite samples, we have determined Ru, Re, Os, Ir and REEs, and confirmed that our values were in agreement with the literature values. Our detection limits for Ru, Re, Os, La, Sm and Eu are significantly low compared with those for ICP-MS.     

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.     

Wet-chemical analysis and determination of trace elements by neutron activation in meteorites

As a contribution to the cosmochemical distribution of elements, 35 meteorites of the collections of the Museum of Natural History in Vienna, the Mineralogical-Petrographical Institute and the Analytical Institute of the University of Vienna were analyzed. In the meteorites main and minor constituents were determined by wet-chemical methods, whereas for the determination of about 16 trace elements neutron activation analysis was employed. This paper has been dedicated to Prof. Dr.J. W. Breitenbach on the occasion of his 60th birthday.     

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.     

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.     

True detection limit of rare earth elements in atomic emission analysis with an arc two-jet plasmatron

The “true detection limit” C_L,true was measured by a method proposed by Boumans et al. for 10 prominent lines of La, Ce, Pr, Nd and Sm, the most abundant rare earth elements (REEs) in geological samples. It is demonstrated how spectral interferences can increase of C_L,true. The spectra were excited in an argon arc plasma jet with evaporation powders of five complex natural samples. The data show that there is a significant increase of C_L,true in real samples containing large concentrations of such elements as Ti, Zr, Cr, Nb, Ta and REEs emitting complex spectra.     

Applicability of capillary electrophoresis to the analysis of trace rare earth elements in geological samples.

This study developed a methodology to analyze trace rare earth elements (REEs) in geological materials by capillary electrophoresis (CE). Changed from dilute HNO3 into a water medium by heating, REE ions are detectable at approximately 2 ng mL(-1). In the presence of coexisting elements from geological samples, REE separations were carried out. After sample fusion with Na2O2 and interference separation with ammonium pyrrolidinedithiocarbamate chelate, REE analytes were coprecipitated with Mg(OH)2 at pH 8.5, and then prepared into a water medium for CE determination. Using the standard addition method, this protocol was validated by analyses with better than 5% precision. This method was applied to geological materials; the REE results are in consistence with their certified values. With electrokinetic injection, internal standard (IS) selected among lanthanides is a prerequisite of high-quality REE data. An approach was proposed to derive the IS content for further correcting its contribution from unknown samples.     

True detection limit of rare earth elements in atomic emission analysis with an arc two-jet plasmatron

The “true detection limit” C_L,true was measured by a method proposed by Boumans et al. for 10 prominent lines of La, Ce, Pr, Nd and Sm, the most abundant rare earth elements (REEs) in geological samples. It is demonstrated how spectral interferences can increase of C_L,true. The spectra were excited in an argon arc plasma jet with evaporation powders of five complex natural samples. The data show that there is a significant increase of C_L,true in real samples containing large concentrations of such elements as Ti, Zr, Cr, Nb, Ta and REEs emitting complex spectra. Received: 17 June 1997 / Revised: 20 October 1997 / Accepted: 26 October 1997     

Measurement of rare earths elements in Kakul phosphorite deposits of Pakistan using instrumental neutron activation analysis

The rare earth elements (REEs) content of Kakul phosphate rock (PR) from different localities of the main Hazara deposits of Pakistan were determined using instrumental neutron activation analysis (INAA). 25 phosphorite samples were collected from different phosphorite sites and 6 samples representing different batches from the crushing plant near Kakul Mine. Concentrations of seven REEs (Ce, Eu, La, Lu, Sm, Tb and Yb) were determined in the PR samples. The highest amounts of Heavy and light rare earth elements (HREE and LREE) were quantified in the PR samples collected at the Phosphate Rock Crushing Plant while the lowest amounts of these REEs were measured in the Lambidogi Phosphorite deposit samples. Comparison with global data showed the REEs content of the studied PRs show lower range for all REEs and mostly comparable to the data reported by Israel and Syria. Calculated chondrite ratio for these elements depicts enrichment of LREEs in all phosphorite deposits.     

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.     

Reliability of prompt gamma-ray analysis for the determination of Na and Mg in rock samples.

The reliability of neutron-induced prompt gamma-ray analysis (PGA) was examined for the determination of Na and Mg in geological and cosmochemical rock samples, because they tend to have been erroneously determined for such samples. JB-1 (basalt standard rock) and Allende (chondritic meteorite) powder samples were repeatedly analyzed by using thermal or cold neutron-guided beams of the JRR-3M research reactor at Japan Atomic Energy Agency. In critically evaluating calculated values for major prompt gamma-rays of Na and Mg, it was observed that a 472.2 keV peak for Na and a 2828.2 keV peak for Mg yielded reasonable consistency with corresponding recommended values. Sodium and Mg were determined for five lunar meteorites by PGA using these prompt gamma-rays, and were found to be consistent with their data obtained by instrumental neutron activation analysis.     

Comparitive study of the sample decomposition procedures in the determination of trace and rare earth elements in anorthosites and related rocks by ICP-MS

ICP-MS has been used for the determination of over 30 geochemically significant trace elements (Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, Ta, Pb, Th, U and REEs) in anorthosites and related rock reference samples. Open acid digestion, pressure decomposition using HF, HNO(3) and HClO(4), and a fusion method using lithium metaborate and subsequent dissolution in dil. HNO(3) were adopted for the decomposition of these rock samples before analysis. The dissolution problems and interference effects are discussed. Rh and Bi were used as internal standards. The first set of data on several rare earths and other trace elements in the Russian anorthosite reference sample, MO-6 are presented along with data on other samples. The data are compared with the available data. The results obtained with different dissolution methods were found to be in good agreement for the majority of the trace elements. The accuracy and precision achieved (better than 6% RSD in most cases) suggested that the data obtained by ICP-MS for such samples are best suited for geochemical interpretations.     

Determination of rare earth elements in geological samples by inductively-coupled plasma atomic emission spectrometry after oxalate coprecipitation and cation-exchange column separation

A method for separation and determination of traces of 14 rare earth elements (REEs) in geological samples is described. Determination by inductively-coupled plasma atomic emission spectrometry follows oxalate coprecipitation of the REEs with calcium as carrier and cation- exchange column separation in nitric acid. The combination of the two separation techniques improved the low recoveries found for Sm, Eu, and Gd when only ion-exchange was used, especially for iron- and aluminum-rich samples. The method was applied to the analysis of geological standard materials NBS SRM 688 (basalt), NBS SRM 278 (obsidian), GSJ JB-1 (basalt), GSJ JA- 2 (andesite), and CCRMP SY-3 (syenite). The results were evaluated on the basis of chondrite- normalized rare earth element distribution patterns.     

Determination of yttrium, scandium and other rare earth elements in uranium-rich geological materials by ICP-AES

A rapid method is described for the determination of yttrium, scandium, and other rare earth elements (REEs) in uranium-rich geological samples (containing more than 0.1% U) and in pitch blende type of samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) after separation of uranium by selective precipitation of the analytes as hydroxides using H(2)O(2)/NaOH in the presence of iron as carrier. Uranium goes into solution as soluble peruranate complex. The precipitated rare earth hydroxides (including Y and Sc) are filtered and dissolved in hydrochloric acid prior to their aspiration into plasma for their individual estimation after selecting interference free REE emission lines. The method has also been applied to some international reference standards like SY-2 and SY-3 (by doping a known amount of uranium) along with one in-house pitch blende sample and the REE values were found to be in agreement with the most usable values, offering an R.S.D. of 1-8.8% for all the REEs', Y and Sc. The method compared well, with the well- established cation exchange separation procedure.     

Determination of cosmochemically volatile trace elements in chondritic meteorites by inductively coupled plasma mass spectrometry

We have developed a method for the quantification of 14 cosmochemically moderately volatile to highly volatile trace elements (Cu, Zn, Ga, Se, Rb, Ag, Cd, In, Sn, Sb, Te, Cs, Tl, and Bi) in chondritic meteorites by ICPMS. The method utilizes internal standardization via addition of Be, Rh, Re, and U and multiple single point matrix-matched external calibrations with Allende standard reference meteorite to provide drift corrected calibration within an ICPMS procedure. We have demonstrated our method's precision and accuracy by performing replicate dissolutions and analyses of 0.05-0.10 g samples of a homogenized sample of the CM2 Murchison meteorite and compared our results to literature values for this meteorite. Our procedure allows for a rapid and accurate determination of the cosmochemically important VTEs in chondritic meteorites providing the means for an even more comprehensive elemental analysis of a single sample of chondritic material.     

Determination of rare-earth elements in a limestone geological standard reference material by ICP-MS following solvent extraction.

Rare-earth elements in a limestone geological standard (JLs-1) were determined by inductively coupled plasma mass spectroscopy (ICP-MS) using phosphoric acid 2-ethylhexyl ester solvent extraction, which had been established for seawater analysis. First, the limestone sample was divided into two fractions: acetic acid soluble (carbonate fraction) and insoluble (residue). A modification of the method was undertaken to achieve quantitative recovery. With this method most of the REEs in the carbonate fraction were quantitatively recovered, except for the heaviest three REEs (Tm, Tb and Lu). The reason for the poor recoveries of the three elements was investigated, but still remained unclear. The mass-spectroscopic interference of BaO with Eu made an accurate determination of both lighter REEs and Eu at the same time impossible. The precision of this method was better than 20%. The data adopted after analytical consideration were consistent with those previously reported.     

Comparitive study of the sample decomposition procedures in the determination of trace and rare earth elements in anorthosites and related rocks by ICP-MS

ICP-MS has been used for the determination of over 30 geochemically significant trace elements (Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, Ta, Pb, Th, U and REEs) in anorthosites and related rock reference samples. Open acid digestion, pressure decomposition using HF, HNO₃ and HClO₄, and a fusion method using lithium metaborate and subsequent dissolution in dil. HNO₃ were adopted for the decomposition of these rock samples before analysis. The dissolution problems and interference effects are discussed. Rh and Bi were used as internal standards. The first set of data on several rare earths and other trace elements in the Russian anorthosite reference sample, MO-6 are presented along with data on other samples. The data are compared with the available data. The results obtained with different dissolution methods were found to be in good agreement for the majority of the trace elements. The accuracy and precision achieved (better than 6% RSD in most cases) suggested that the data obtained by ICP-MS for such samples are best suited for geochemical interpretations.     

Radiochemical neutron activation analysis of trace lanthanoids in geological and cosmochemical samples

In order to determine trace lanthanoids in geological and cosmochemical samples, an analytical procedure for radiochemical neutron activation analysis (RNAA) was developed, where lanthanoids are radio-chemically purified through precipitations of hydroxides and fluorides, and cation exchange using HBr as an eluent. Chemical yields are determined by reactivation. The procedure was applied to the Allende meteorite and geological standard rocks. Our data for Allende are in excellent agreement with literature values, and those values for standard rocks, JP-1 (peridotite) and JF-2 (feldspar), in which lanthanoids are depleted by orders of 1 to 2 compared with those in Allende, seem to be reasonable, although not properly evaluated because of large scatterings in their literature data. This suggests that the present RNAA procedure is highly effective in determining trace lanthanoids (less than 1 ng) in rock samples.     

Determination of trace rare earth elements by inductively coupled plasma atomic emission spectrometry after preconcentration with multiwalled carbon nanotubes

A new method has been developed for the determination of trace rare earth elements (REEs) in water samples based on preconcentration with a microcolumn packed with multiwalled carbon nanotubes (MWNTs) prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). The optimum experimental parameters for preconcentration of REEs, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been investigated. The studied REEs ions can be quantitatively retained by MWNTs when the pH exceed 3.0, and then eluted completely with 1.0 mol L⁻¹ HNO₃. The detection limits of this method for REEs was between 3 and 57 ng L⁻¹, and the relative standard deviations (RSDs) for the determination of REEs at 10 ng mL⁻¹ level were found to be less than 6% when processing 100 mL sample solution. The method was validated using a certified reference material, and has been successfully applied for the determination of trace rare earth elements in lake water and synthetic seawater with satisfactory results.     

Rare earths elements in phosphorite and granulated single super-phosphate fertilizers of Pakistan,a study using instrumental neutron activation analysis

Sensitive nondestructive instrumental neutron activation analysis (INAA) technique has been applied for the determination of rare earth elements (REEs) (Ce, Eu, La, Lu, Sm, Tb and Yb) in phosphate rocks (PR) and granulated single super-phosphate (GSSP) fertilizer samples from Hazara district of Pakistan. The comparison of the PR with product fertilizers shows that most of the quantified REEs were found to be in lower contents in the fertilizers. Six fertilizer samples with different N, P and K ratio for distinctive application to plants were also characterized. The REEs in these showed irregular patterns that can be attributed to difference in their manufacturing and chemical processes. The REEs contents of local phosphate fertilizer were found to be lower in comparison to the values cited in the literature; however Ce is relatively high. For quality assurance fair agreement was found between the results obtained for reference materials IAEA SL-1 (Lake Sediment) and GSJ-JR-1 (Rhyolite).