Analysis of trace elements in trunk wood by thick-target PIXE using dry ashing for preconcentration

Thick-target Particle Induced X-ray Emission (TTPIXE) was used for the quantitative determination of trace-element concentrations in trunk wood. The wood samples were preconcentrated by dry ashing to improve the reliability of the sampling and the sensitivity of the analytical method. Samples of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) were collected from a polluted area (Harjavalta) as well as from a relatively nonpolluted area (Merimasku) in southwestern Finland. The elements studied were P, S, K, Ca, Mn, Fe, Ni, Cu, Pb, Rb, Sr, Ba, Cd and Ag. TTPIXE combined with dry ashing is a sensitive and reliable analytical technique for most elements studied. The method was validified by using several certified reference materials and also by ICP-MS analysis. Due to the low ash content (0.2–0.4%) in wood a high preconcentration factor can be obtained. Differences in trace-element uptake were observed between the two tree species studied. Trunk wood from the polluted area contained higher concentrations of heavy metal ions. Received: 30 August 1996 / Revised: 11 October 1996 / Accepted: 3 November 1996     

Estimation of trace elements in some anti-epileptic medicinal plants by PIXE

Trace elemental analysis was carried out in various parts of 10 anti-epileptic medicinal plants using PIXE technique. A 3?MeV proton beam was used to excite the samples and spectra were recorded using a Si(Li) detector. Data analysis was done using Gupix Software. The elements Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br and Sr were identified and their concentrations estimated. The presence of some of these trace elements is correlated with the anti-epileptic curative property of these plants.     

Losses of elements in plant samples under the dry ashing process

Losses of trace elements in plant samples after dry ashing were investigated. Plant samples were heated in crucibles at 105–600°C for 0.5–24 hours in a muffle furnace. The amounts of elements remaining after heating were determined by INAA. The amounts of Cl and Br decreased over the range 200–400°C in all samples, especially in stem samples. The amount of Na increased over the range 450–600°C, possibly because of contamination from the crucibles. Dry ashing is suitable for analyzing most elements in plant samples.     

Evaluation of concentrations of major and trace elements in human lung using INAA and PIXE

The elemental concentrations of Br, Ca, Ce, Cl, Co, Cr, Cs, F, Fe, Hf, K, Mg, Mn, Na, O, Rb, Sb, Sc, Se, V and Zn in 15 human lung autopsy samples, taken from subjects aged more than fifty years old, were determined by instrumental neutron activation analysis (INAA) using reactor neutrons in conjunction with a high resolution detection system. Two modes of irradiation and counting were applied; namely cyclic neutron activation analysis (CNAA) and conventional neutron activation analysis. Proton induced X-ray emission (PIXE) analysis, using a proton beam emerging from a 2 MV Van de Graff accelerator, was additionally employed and Ge, Ni, P and Ti were also identified in the lung tissue. Detection of the X-ray spectra was performed using a high resolution Si(Li) semiconductor. The relevance of these results, including a comparison between the concentrations of elements measured in a pig's lung using CNAA and those found in the human lung is discussed.     

PIXE analysis of the hydrothermal leaching of trace elements in coal

The minor and trace element content in coal is of great interest due to the potential impact on the environment from the release of these elements during combustion. Reducing the concentrations of potentially hazardous elements in coal prior to combustion is one way of dealing with this issue. In this research particle induced X-ray emission (PIXE) was used to investigate a hydrothermal leaching process for the removal of trace elements from a bituminous coal. The leaching agents HNO₃ and NaOH were evaluated along with the effects of process parameters (temperature, pressure, and time) on the method's effectiveness. The variable with the greatest influence was the leaching agent itself. HNO₃ was determined to be more effective than NaOH in reducing elemental concentrations for nearly all the elements determined. Increasing the temperature did result in greater reductions for some elements (Cl, Br, Zn) whereas increasing the pressure and duration of the leaching process had minimal impact on reductions, in elemental concentrations.     

Determination of major and trace elements in bones by simultaneous PIXE/PIGE analysis

The training process and training programs in both commercial nuclear plants and Department of Energy (DOE) nuclear facilities have improved significantly in the years following the Three-Mile Island (TMI) accident. This article describes some of these changes, including the reasons behind the change, the affected population, the training accreditation process and performance-based training, and the benefits of the changes.     

Polyurethane-pyridylazonaphthol foams in the preconcentration and separation of trace elements

The feasibility of using PAN—polyether and polyester polyurethane foams in batch and column operations has been examined. The effects of pH, plasticizer and various anions present in the aqueous solution on the extraction behaviour of cobalt, iron and manganese have been investigated. In dynamic systems, the effect of flow rate on the extraction efficiencies of these metal ions has been investigated. The uptake of cobalt(III) and manganese(II) on PAN—polyester foam columns is quantitative at flow rates up to 10 ml min^-1 and 2 ml min^-1, respectively. The retention of iron(III) by the foam column is not quantitative even at a flow rate of 1 ml min^-1. Preconcentration of cobalt and its separation from various concentrations of manganese are successful..     

Investigation on the preconcentration of trace elements on polyacrylonitrile

Summary Trace amounts of Co, Ni, and Mn have been enriched from aqueous solutions by retention of their ions on polyacrylonitrile (PAN). The recovery has been determined as a function of the amount of PAN, pH, the concentration of eluent (HCl) and the volume of sample solution. The elements were removed with 100% efficiency by means of conc. HCl. Recoveries were up to 95% depending on the elements. The resin has been used in combination with atomic absorption spectrophotometry for the determination.     

Determination of trace amounts of rare earth elements by neutron activation analysis after preconcentration using hydrated magnesium oxide

A preconcentration method of 13 rare earth elements (REES) was studied for neutron activation ananlysis (NAA). Hydrated magnesium oxide was used as the preconcentration agent to absorb the REES ions from aqueous solution onto the solid magnesium oxide, which was separated and analyzed. It was observed that the Langmuir equation for isothermal adsorption was well obeyed by the REES under the condition studied. The efficiency of the preconcentration process using hydrated magnesium oxide was critically examined for each of REE and for mixture of REES by preparing a known volume of solution containing known amount of trace REES. NAA was used to analyze REES recovered by the preconcentration process. It was found that the REES recoveries were satisfactory and the preconcentration process is reliable. There are several resort resort areas in Taiwan where local people are enjoying its hot spring water. It is generally believed that the hot spring water spa would bring about some sorts of therapeutic functions. The preconcentration method developed above, was applied to analyze the trace amounts of REES in hot spring wate in Taiwan.     

The determination of trace elements in aqueous media without preconcentration using a cryogenic hollow-cathode ion source

The glow discharge in a hollow cathode containing 20–50 μl of an aqueous sample held at liquid-nitrogen temperature is used as a source of ions in a double-focussing mass spectrometer. The device was tested with nine solutions containing an aggregate of seventy elements. Seven elements (F, P, S, Sc, Mn, Ni, and Ta) could not be determined because of interferences. The remainder of the elements could be determined at various detection limits ranging from sub-ng ml^?1 to μg ml^?1. Mercury (32 pg) could be detected in 20 μl of water in the presence of Tl, Pb, Bi, Th, U, and Al.     

The status of trace and minor elements in pulses: A PIXE measurement

The proton particle induced X-ray emission (proton PIXE) technique has been employed to study the heavy element status (essential and toxic) in five different varieties of pulses commonly cultivated and consumed in Bangladesh. In this analysis, the samples were irradiated in air with 2 MeV protons having 30 nA beam intensity for characteristic X-ray excitation. For 40 μC irradiations, the concentration of ten elements (K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br, and Rb) was determined by comparison with a calibration obtained from the NBS orchard leaf standard, SRM 1571. In a comparative study with atomic absorption spectrophotometric (AAS) measurements of some elements in lathyrus sativus, the data were found to be in good agreement. The results obtained from the present study are discussed and compared with available data.     

Preconcentration of trace elements by partial dissolution of the matrix—multielement preconcentration from manganese

Trace elements such as Ag, Au, Bi, Cd, Co, Cu, Fe, Ga, In, Ni, Pb, Pd and Tl, can be preconcentrated with recoveries of better than 95% from high-purity manganese if the sample is coated with a thin layer of mercury before its dissolution in HCl to a small residue. For determination of the trace elements, the residue is completely dissolved in aqua regia. After separation of the mercury by reductive precipitation, Bi, Cd, Co, Cu, Fe, Ga, In, Ni, Pb, and Tl are determined by flame a.a.s. ('injection method'). Ag, Au and Pd are determined in the mercury-containing solution. The relative standard deviation was usually about 5%; Cu, Fe and Pb were proved to be inhomogeneously distributed in the sample (electrolytically produced manganese), and so the standard deviations were considerably greater. The detection limits for the different elements were between 0.6 and 0.004 ppm, depending on the sensitivity of their a.a.s. determination. The theoretical basis of this preconcentration method and its applicability to multielement analysis of different high-purity metals are discussed.     

Simultaneous separation and preconcentration of trace elements in water samples by coprecipitation on manganese dioxide using D-glucose as reductant for KMnO(4)

A field oriented and economical method of coprecipitation of trace elements like Al, Au, Bi, Cd, Co, Cu, Fe, Mo, Ni, Pb, Pd, Ti, V, W, Zn and REE has been developed. A novel reductant D-glucose, reduces KMnO₄ in solution to form a precipitate of MnO_2. Two liters of clear natural water sample is adjusted to pH 3.5–4.0, and is treated with 10 ml of 1% KMnO₄ and 20 ml of 0.1% D-glucose. The sample is heated at a temperature of 75–80 °C, MnO₂ is formed which coprecipitates the above trace elements. The precipitate is separated by filtration, dissolved in 2 ml of 50% HCl and 2 ml of 30% H₂O₂ and diluted to 25 ml for analysis using AAS and ICP-AES. The recoveries were found to be 96–105%. The preconcentration factor is 80. Limits of determination by the proposed method in natural waters are 1 μg l⁻¹ for Al, Cd, Mo, V, W, Ti and Zn, 5 μg l⁻¹ for Au, Bi, Co, Cu, Fe, Ni, Pb and Pd and 8 μg l⁻¹ for REE. The RSD of the present procedure (n=5) is 8% at 5 μg l⁻¹ level. Twenty water samples can be analyzed by an analyst in an 8-h day.     

Determination of trace elements in sea water by graphite-furnace atomic absorption spectrometry after preconcentration by tetrahydroborate reductive precipitation

A method is described for the preconcentration of 16 elements from coastal and deep ocean sea water based on their reductive precipitation by sodium tetrahydroborate. The enrichment factors obtained were sufficient to permit the analysis of a near-shore sea-water reference material (11 elements) and an open ocean sea-water reference material (9 elements). Recoveries from 900 ml of sea water ranged from 80 to 107% (100-ml sample for Mn) with absolute blanks between <1.0 ng (Se) and 20 ng (Cu). Estimated detection limits varied from 0.3 ng l ^?1 (Pb) to 19 ng l^?1 (As) based on a 36-fold concentration of a 900-ml sample.     

Thick-target PIGE analysis of plant materials preconcentrated by dry ashing

An analytical methodology has been developed for the UV-spectrophotometric determination of carbaryl in waters after its preconcentration onto a polyether type polyurethane foam followed by on-line elution. The aforementioned strategy offers an easy way for in-field sampling and to improve the analytical sensitivity. Several chemical and flow variables (mass of sorbent, sample flow rate, sample volume and carrier flow rate) were studied to ensure the best performance of the system. Recovery studies, carried out on natural water samples spiked with known amounts of carbaryl at concentration levels between 250 and 500 mug l(-1), provided recovery percentages between 94 and 105%. A detection limit of 12 mug l(-1) was achieved and a variation coefficient of 3.4% was obtained at 0.50 mug ml(-1).     

A solid phase extraction using a chelate resin immobilizing carboxymethylated pentaethylenehexamine for separation and preconcentration of trace elements in water samples

A chelate resin immobilizing carboxymethylated pentaethylenehexamine (CM-PEHA resin) was prepared, and the potential for the separation and preconcentration of trace elements in water samples was evaluated through the adsorption/elution test for 62 elements. The CM-PEHA resin could quantitatively recover various elements, including Ag, Cd, Co, Cu, Fe, Ni, Pb, Ti, U, and Zn, and rare earth elements over a wide pH range, and also Mn at pH above 5 and V and Mo at pH below 7. This resin could also effectively remove major elements, such as alkali and alkaline earth elements, under acidic and neutral conditions. Solid phase extraction using the CM-PEHA resin was applicable to the determination of 10 trace elements, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn, in certified reference materials (EnviroMAT EU-L-1 wastewater and ES-L-1 ground water) and treated wastewater and all elements except for Mn in surface seawater using inductively coupled plasma atomic emission spectrometry. The detection limits, defined as 3 times the standard deviation for the procedural blank using 500 mL of purified water (50-fold preconcentration, n = 8), ranged from 0.003 μg L⁻¹ (Mn) to 0.28 μg L⁻¹ (Zn) as the concentration in 500 mL of solution.     

Anion exchangers functionalized by chelating reagents (AnChel) for preconcentration of trace elements: Capabilities and limitations

Summary Conventional anion exchangers (e.g., Adsorbex SAX, Amberlite IRA 410, Dowex 1X8, Lewatit MP 5080, TEAE cellulose) functionalized by means of sulfonated metal reagents (e.g., Arsenazo III, Eriochrome Red B, 8-hydroxyquinoline-5-sulfonic acid, Tiron and others) were investigated as collectors (AnChel) for analytical preconcentration of trace elements. In particular, the stability of AnChel strongly depending on competing anions, on the anion exchanger and on the metal reagent chosen, was characterized. Accordingly, for appropriate combinations of AnChel (e.g., Dowex 1X8/Arsenazo III) reagent distribution coefficients K_d in the range 10⁴ to 10⁵ (ml/g) could be attained on polystyrene-based anion exchangers even in concentrated salt solutions (e.g., 4 mol/l NaCl), but not on hydrophilic exchangers (e.g., SAX, TEAE cellulose). In general, the stability of AnChel against competing anions followed the order Cl^–>SO ₄ ^2– >NO ₃ ^– >ClO ₄ ^– . Reagent loadings of about 1 mmol/g (e.g., 8-hydroxyquinoline S) on the anion exchangers were obtainable. Trace metals precomplexed with the reagents cited could be separated (>90%) within 5 min and remobilized by acid (e.g. 2 mol/l HNO₃) within some 10 s (batch procedure). Using small columns filled with anion exchanger (e.g., 0.25 g Dowex 1X8) fast trace-matrix separations were carried out with 8-hydroxyquinoline S (Cu, Fe, In, Mn, Pb, Zn) in MgCl₂ solutions and with Arsenazo III (U, Th) in AlCl₃ solution, respectively. For subsequent trace determinations the flame-AAS (injection technique) was applied, except for Th and U [quantified by total reflection X-ray fluorescence (TXRF)].     

Speciation of some trace elements in water samples after preconcentration on activated carbon by neutron activation analysis

A new filtering column has been developed on the covalent attachment of chelating functionalities to simple, highly hydrophilic adsorbent material, which can then complex heavy metal ions irreversibly and targeted towards toxic metals removal. The capacity of the chemically modified sorbent (modified charcoal) materials used in this work was evaluated for the above mentioned heavy metal ions in the presence of iron ions and simulated water samples. The methods are based on preconcentrations of the elements of interest on activated carbon and zirconium loaded activated carbon using specific conditions of pH and oxidation states followed by a final determination by neutron activation analysis (NAA). It has been investigated that zirconium loaded activated carbon is able to adsorb As (V), Se (VI), Cr (VI) and Hg (II) at any pH while activated carbon is able to adsorb As (III), Se (IV), Cr (III) and Hg(I) at higher pH. This revised version was published online in August 2006 with corrections to the Cover Date.