Trace element determination in thorium oxide using total reflection X-ray fluorescence spectrometry

Applicability of Total Reflection X-ray Fluorescence (TXRF) spectrometry for the determination of trace metals at concentration of µg/g level in thorium oxide was studied. The TXRF spectrometer was calibrated using a multielement standard solution and the method was validated by analyzing another multielement standard solution. Sample preparation conditions were optimized for the TXRF determinations of trace metals in thorium oxide. The elements K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Ba and Pb present in thorium oxide standards were determined after dissolving them in HNO₃/HF mixture and separating the bulk matrix, thorium, by solvent extraction using tri-n-butyl phosphate (TBP) and tri-n-octyl phosphine oxide (TOPO) as extractants. A comparison of TXRF determined concentrations of trace elements Ca, V, Cr, Mn, Fe, Ni and Cu with the certified values shows that TXRF determined concentrations have an RSD of 20% (1 s for n = 4) and are within an agreement of 20% of the certified values in most of the cases.     

Trace metal enrichment by automated on-line column preconcentration for flow-injection atomic absorption spectrometry

An on-line column preconcentration technique for flow-injection atomic absorption spectrometry was developed. Diverse metal ions (Cd²⁺, Zn²⁺, Cu²⁺, Mn²⁺, Pb²⁺, Fe³⁺ and Cr³⁺) in solution were concentrated quantitatively by a microcolumn (7-mm × 4-mm i.d.) packed with Muromac A-1, which is an iminodiacetate chelate resin, in a flow-injection system. From the pH dependence of the uptake of the ions, all the divalent metals examined were recovered quantitatively in the pH range 3–5 and the trivalent metals were recovered at a maximum pH of 1. Enrichment factors using 20-ml samples were in the range 90–180-fold for the seven elements and the sampling rate was 13 h^?1. The 3σ detection limits were in the range 0.14–2.1 μg l^?1 and the relative standard deviations for replicate measurements (n=3–4) were in the range 0.7–1.7%. The method was compared with flame and graphite furnace atomic absorption spectrometry. Application to the determination of cadmium and copper in several standard reference materials is described.     

Analysis of molybdenum oxide by inductively coupled plasma atomic emission and mass spectrometry

Procedures for the analysis of molybdenum oxide by of inductively coupled plasma atomic emission spectroscopy (ICP-AES) and mass spectrometry (ICP-MS) are proposed on the basis of preliminary extraction separation of molybdenum from impurity elements. To separate 39 impurity elements (Li, Be, Na, Mg, Al, K, Ca, Sc, Ti, Cr, Mn, Fe, Co, Ni, Zn, Ga, Rb, Sr, Y, Cd, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb, Bi, Th, and U), the extraction of molybdenum from hydrochloric acid solutions using 5-n-pentylthio-8-hydroxyquinoline was used. The capacities of both methods ICP-AES and ICP-MS in the analysis of molybdenum oxide analysis were examined without the removal of the matrix and after the extraction separation of molybdenum.     

Rapid accurate analysis of metal (oxide)-on-silica catalysts by atomic absorption spectrometry

The catalysts, which contain 10–60% copper, chromium, nickel and silicon, are decomposed in sealed Teflon-lined vessels and analyzed by atomic absorption spectrometry. Matrix matching and bracketing standards are applied. The RSD of a single determination is about 1% for all components.     

Determination of phosphorous in organic compounds and metal complexes by inductively-coupled plasma atomic emission spectrometry

Phosphorus is determined by inductively-coupled plasma atomic emission spectrometry at 213.618 nm. Different types of organic and inorganic phosphorus compounds and metal complexes were examined after direct dissolution in water, aqueous ethanol or acid, or after decomposition by oxygen flask combustion or Kjeldahl digestion; results were within the usual limit of precision and accuracy for such determinations. The effect of small (<20%) ethanol concentrations in the aqueous solution on the signals obtained from a low-power (1200 W) argon plasma is examined and discussed.     

Trace determination of nickel by microwave-induced plasma atomic emission spectrometry after preconcentration of nickel tetracarbonyl on Chromosorb

A method is presented for the determination of ultra-trace nickel concentrations in various samples. Ni²⁺ is reduced in aqueous solution by tetrahydroborate to Ni⁰, which reacts readily with carbon monoxide to give gaseous Ni(CO)₄, the latter being preconcentrated on Chromosorb, cooled by liquid nitrogen. After desorption of the carbonyl by electrically heating the Chromosorb trap, it is swept by argon to the microwave-induced plasma (hollow-cylinder O₂-Ar MIP with Beenakker resonator). Using this technique, nickel detection is possible without any interferences, because other carbonyl-forming reactions are too slow. The detection limit is 5 pg (3σ), corresponding to 5 ng l^?1, and the relative standard deviation is 3% at 100 pg. The method was applied to sea water and urine without digestion and whole blood, blood serum and human hair after decomposition by HNO₃-HClO₄.     

Tungsten coil atomic emission spectrometry

A tungsten coil atomic emission spectrometer is described and evaluated. The system employs a single tungsten coil as a combined atomizer and excitation source for the determination of metals by atomic emission spectrometry. The tungsten coil is extracted from a 150 W, 15 V commercial slide projector light bulb. A simple, laboratory constructed, computer-controlled power supply provides a constant current to the coil. A high-resolution Czerny–Turner monochromator with a charge coupled device detector completes the system. Simultaneous, multi-element analyses are possible within a 4 nm spectral window. Eleven test elements are used to characterize the system: Al (396.1 nm), Co (353.0 nm), Cr (427.1 nm), Dy (404.6 nm), Ga (403.3 nm), K (404.4 nm), Mn (403.1 nm), Pb (405.8 nm), Rb (420.2 nm), Sc (404.8 nm), and Yb (398.7 nm). Tungsten coil atomic emission detection limits are reported for these elements for the first time: 0.02 ng Al, 0.7 ng Co, 0.003 ng Cr, 0.01 ng Dy, 0.7 ng Ga, 0.3 ng K, 0.04 ng Mn, 10 ng Pb, 0.07 ng Rb, 1 ng Sc, and 0.003 ng Yb. The precision for the new technique is better than 13% relative standard deviation for all metals at concentrations two orders of magnitude above the detection limit. Aluminum, Cr, Mn, and K are determined in a standard reference material (trace elements in water) after simple dilution with water, and found values varied from certified values by up to 26%. The average tungsten coil lifetime was found to be 265 heating cycles. The elimination of the external radiation source needed for atomic absorption measurements results in an emission system that could be quite portable.     

Trace metal contents in certified reference sediments determined by nitric acid digestion and atomic absorption spectrometry

The trace metal (Cd, Cu, Pb, Zn, Fe) contents of certified reference sediments BCSS-1, MESS-1, SRM 1645 river sediment and SRM 1646 estuarine sediment) were determined by nitric acid digestion at 140°C without silicate lattice dissolution. All the metals studied except iron were completely recovered by this digestion method. About 20% of the iron was not recovered under the given conditions. The trace metal contents in SRM 1645 were also examined by using the hydroxylammonium chloride/acetic acid leaching procedure.     

Determination of trace impurities in uranium, thorium and plutonium matrices by solvent extraction and inductively coupled plasma atomic emission spectrometry

Studies on the determination of trace metallic impurities in nuclear materials such as uranium, thorium and plutonium are described. The bulk of the matrix is separated by batch extraction from their nitric acid solutions using 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate (KSM-17, equivalent to PC88-A). The final aqueous phase containing the metallic impurities is fed to a high-temperature source inductively coupled plasma and the analysis is carried out employing a computer-controlled multichannel direct-reading spectrometer. The studies also included the recovery of impurities at various acidities and spectral interferences of the above matrices over the analyte elements. Based on the above studies, methods were standardized for the determination of 19 elements, viz. Al, B, Be, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Si, Zn, Ce, Dy, Eu, Gd and Sm, in U/Th/Pu solutions. The relative standard deviation for various elements is in the range 1-5%.     

High-pressure microwave dissolution of ceramics prior to trace metal determinations by microwave induced plasma atomic emission spectrometry

A commercial laboratory microwave acid digestion system was evaluated for the acid dissolution of ceramic powders (Al₂O₃, AlN, BN and Si₃N₄) prior to the determination of their trace element content by microwave induced plasma atomic emission spectrometry. Newly designed vessels, capable of withstanding internal pressures of over 110 bar, provide rapid and satisfactory results for sample dissolution. Sample preparation time was approximately 30 min (including the subsequent cooling time and preparation of the final solution). Results from conventional stainless-steel acid digestion vessel (Teflon bomb) dissolution are compared with the microwave bomb results of microwave plasma atomic emission spectrometry.     

Indirect determination of iodide by tungsten coil atomic emission spectrometry

The spectroscopic determination of iodide is a difficult challenge, especially in small sample volumes. The strongest transition lines for this element lie in the vacuum ultraviolet region of the spectrum, so most conventional instruments produce very weak signals. This work describes a tungsten coil atomic emission procedure for the indirect determination of iodide. A 25 μl aliquot of a solution containing a known amount of indium is deposited on the tungsten coil and dried with a simple heating program. Once the coil is dry, 25 μl of an iodide solution is added to the coil. The solution is dried and vaporized at high current. The atomic emission signal for In at 451.1 nm is monitored. In the presence of iodide, InI is formed and the In emission signal is attenuated. This attenuation is proportional to iodide concentration with a method detection limit of 0.6 mg l^{− 1} iodide using an In concentration of 10 mg l^{− 1}, and 3 mg l^{− 1} iodide using an In concentration of 50 mg l^{− 1}. Linear calibration curves span a range of two orders of magnitude. Analysis of a deionized water sample spiked with 50 mg l^{− 1} iodide gives a recovery of 100% and a precision of 5.5% relative standard deviation. Analysis of a tap water sample spiked with 50 mg l^{− 1} iodide gives a recovery of 140% and a precision of 7.1% relative standard deviation. The poor accuracy for the tap water analysis may arise from the reaction of In with other halides in the sample. This is the first report of determination of a halogen using the tungsten coil atomizer.     

Trace metal determinations in estuarine waters by electrothermal atomic absorption spectrometry after extraction of dithiocarbamate complexes into freon

Cadmium, copper, iron, lead, nickel and zinc are determined. The dithiocarbamate complexes of the metals are extracted into Freon-TF and back-extracted into dilute nitric acid solution. Portions of the back-extracts are injected into a graphite furnace. The method gives complete separation from the matrix irrespective of salinity. It is therefore useful throughout the full salinity range of an estuary, 0–35‰.The effect of high iron concentrations on the extraction is eliminated by using a mixed acetate buffercomplexing agent solution.     

Determination of tungsten by direct current plasma atomic emission spectrometry

The determination of tungsten in steels and alloys with the three-electrode direct current plasma (DCP) “spectrajet” was investigated. The relative intensities of 17 spectral lines of tungsten and several possible interfering lines of its concomitants are listed. WI 400.875 nm is normally best suited, because the background produced by iron and acid is low and easily compensated for by using a blank solution. The limit of detection c_l in steels is 2 × 10^?3% W for 10 $\text{mg}\text{ml}$ of sample. The line W I 407.436 nm is preferred in the presence of much titanium. For the purpose considered the DCP provides about the same power of detection as the more expensive inductively coupled plasma (ICP), but its observation zone is less well buffered against influences from the matrix.     

Comparative determinations of lead in soils by X-ray fluorescence, atomic absorption spectrometry, and atomic emission spectrometry

Summary Determinations of lead in different soil samples were carried out by X-ray fluorescence (XRF) (borate-glass fusion 13), atomic absorption spectrometry (AAS), and induced coupled plasma atomic emission spectrometry (ICP-AES) (aqua regia digestion). The concentration ranges in contaminated soils were 10 to 200 wt. ppm and 0.05 to 3.0 wt.%. The detection limit of XRF (5 ppm) is adequate; the precision of AAS (1%) is the best; but the relative accuracy of all three methods does not surpass 10%. This is because of errors in sampling and sample preparation, the latter being difficult to judge. Determinations with different methods and correlation analysis of the results are necessary.

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Vergleichende Bestimmung von Blei in Böden durch Röntgenfluorescenz, AAS und AES

Zusammenfassung Bleibestimmungen in verschiedenen Bodenproben wurden mit der RFA (Boratglas-Schmelze 13), AAS (Königswasser-Aufschluß) und ICP-AES (Königswasser-Aufschluß) durchgeführt. Die Konzentrationsbereiche waren 10 bis 200 Gew.-ppm und 0,05 bis 3,0 Gew.-% in kontaminierten Bodenproben. Die Nachweisgrenze der RFA (5 ppm) ist ausreichend; die Reproduzierbarkeit der AAS (1 %) ist die beste, aber die Richtigkeit der drei Methoden ist nicht besser als 10% relativ. Gründe dafür sind Fehler bei der Probenahme und bei der Probenvorbereitung; letztere sind schwer zu erkennen. Bestimmungen mit mehreren Methoden und Korrelationsanalyse der Resultate sind notwendig.

     

Determination of copper in milk powder by electrothermal atomic absorption and atomic emission spectrometry

Summary Electrothermal atomic absorption spectrometry (ETA-AAS) and atomic emission spectrometry (ETA-AES) have been applied to the determination of copper in powdered milk. A homogeneous dispersion procedure for the preparation of the milk powder is described which was found to be simple, rapid and less susceptible to contamination than dry ashing or wet digestion methods. Both ETA-AAS and ETA-AES techniques were found to provide satisfactory results using conventional tube wall atomisation only when the method of standard additions was employed. The application of graphite probe atomisation in ETA-AES and ETA-AAS allowed the development of direct methods for the determination of copper in milk powder using aqueous standard calibration curves. The accuracy of the probe ETA-AAS method was confirmed using new reference materials prepared by the EEC Community Bureau of Reference. Acceptable agreement was obtained for the other procedures using a commercial milk powder sample with a copper content of 6.0g g^–1.     

Determination of phosphorus in waste-waters by inductively-coupled plasma atomic emission spectrometry

Inductively coupled plasma—atomic emission spectrometry offers a simple and rapid method for the determination of total phosphorus in waste-waters: the optimum operating conditions are described. The detection limits are 0.02, 0.04, and 0.11 μg ml^-1 at the 213.618, 214.914, and 253.565-nm lines, respectively. Interferences by other elements are negligible at the concentration levels of these elements in environmental and waste-waters, except for the spectral interference of copper on the lines at 213.618 and 214.914 nm. Differences in emission response for various inorganic and organic phosphorus compounds are small. Analytical results for phosphorus in municipal and industrial waste-waters agree well with those obtained by standard methods.     

有机溶液进样大功率微波诱导空气等离子体发射光谱法测定金属离子的研究

研究了由Okamoto腔产生的大功率微波诱导空气等离子体的分析性能以及用该等离子体直接有机溶液进样测定有机溶剂或含有大量有机溶剂的废水中的金属污染物的可行性。用本方法测定了几种工业废水中的金属污染物,并与原子吸收光谱法的测定结果进行了比较。