Investigating the antimony determination in environmental samples by NAA

In recent years, environmental concerns regarding antimony have grown considerably due to anthropogenic processes that have resulted in increasing concentration of Sb in the environment, and also because of its impacts and possible adverse effects to living organisms. Several techniques have been used, to obtain reliable results for Sb, since Sb is present at low level concentration, requiring analytical instrumentation with low detection limits. The neutron activation analysis (NAA) technique has a high metrological level for the determination of several elements in different matrices. However, Sb determination in environmental and biological samples presents some analytical difficulties due to its low concentrations and gamma ray spectrum interferences. The objective of this research was to study on Sb determination in environmental reference materials by NAA. Ten environmental reference materials were selected and analyzed using long period irradiation at IEA-R1 research nuclear reactor. The induced gamma activities of ¹²²Sb and ¹²⁴Sb were measured. Relative errors of the results demonstrated that the accuracy depends mainly on Sb radioisotope measured, the decay time for counting and the sample composition.     

Application of prompt gamma-ray spectrometry to helium-3-induced activation of boron

An assessment was made of the analytical potential of the exoergic reactions on boron, induced by³He⁺ beams. Possible interferences from C, N and O were studied. Gamma-rays originating from (³He, n), (³He, d), (³He, d), (³He, ) and Coulomb excitation were identified. Possible practical applications in boron studies are indicated.     

Zur borbestimmung in silizium und germanium durch aktivierung mit protonen und deuteronen

The determination of boron via the nuclear reaction ¹¹B(p,n)¹¹C was studied in detail; the nitrogen reaction ¹⁴N(p,a)¹¹C interferes. Nitrogen also interferes deuteron activation via the nuclear reactions 10B(d,n)¹¹C and ¹¹B(d,2n)¹¹C, this interference must be attributed to the nuclear reaction ¹⁴(d,αn)¹¹C. Both interferences were investigated quantitatively. The conditions for the accurate determination of boron and for a simultaneous determination of boron and nitrogen by proton activation were established. An analytical method with chemical separation of the radioisotope ¹¹C was developed for silicon and germanium.     

NAA methods for determination of nanogram amounts of arsenic in biological samples

Summary The determination of arsenic at natural levels in biological materials remains difficult. Many analytical techniques cannot detect the low levels present in typical biological tissues and other techniques suffer from interferences. This paper reviews uses of neutron activation analysis (NAA) at NIST to determine nanogram amounts of arsenic in biological reference materials with radiochemical (RNAA) or instrumental (INAA) procedures. INAA is compromised by high activities from ²⁴Na, ⁸²Br, and ³²P that may be formed during irradiation of biological tissues, and result in detection limits as high as 0.1 mg. Lower detection limits have been achieved using state-of-the-art gamma-ray spectrometry systems in INAA and a variety of procedures in RNAA. These techniques and procedures were applied recently at NIST to the determination of arsenic in urine, nutritional supplements, and total diet samples.     

Etude des possibilites de dosage du lithium par activation au moyen de protons et de deutons de moyenne energie

The determination of lithium by measuring⁷Be, produced by proton or deuteron activation, has been studied. The extent of interference from boron or beryllium, which also form⁷Be, was measured. The calculated sensitivity limits when activating for one hour with 10μA beams of 14 MeV protons or 25 MeV deuterons are, for lithium, 1·10⁻¹ and 2.5·10⁻² ppm and for boron, 2·10⁻¹ and 1·10⁻¹ ppm, respectively.      

Automated method for the determination of boron in water by flow-injection analysis with in-line preconcentration and spectrophotometric detection

A sensitive, automated method for the determination of boron in water samples is described, involving flow injection with on-line ion-exchange preconcentration and spectrophotometric detection of the azomethine-H—boron complex. The method is applicable to various water samples and is free from interferences, even in coloured samples. Detection limits of 5 μg l^?1 at 20 samples h^?1 and 1 μg l^?1 at 10 samples h^?1 with relative standard deviations of < 10% at 1–10 μg l^?1 and < 5%at 10–200 μg l^?1 levels of boron were achieved. The recoveries for spiked natural water samples ranged from 96 to 101%. The method compares favourably with inductively coupled plasma atomic emission spectrometry.     

Lithium ions determination by selective pre-concentration and differential pulse anodic stripping voltammetry using a carbon paste electrode modified with a spinel-type manganese oxide

The use of selective pre-concentration and differential pulse anodic stripping voltammetry (DPASV) using a carbon paste electrode modified (CPEM) with spinel-type manganese oxide has been proposed for the determination of lithium ions content in natural waters. The new procedure is based on the effective pre-concentration of lithium ions on the electrode surface containing spinel-type Mn(IV) oxide with the reduction of Mn(IV) to Mn(III) and consequently the lithium ions intercalation (insertion) into the spinel structure. The best DPASV response was reached for an electrode composition of 25% (m/m) spinel-type MnO₂ in the paste, 0.1 mol l⁻¹ tris(hydroxymethyl)aminomethane (TRIS) buffer solution of pH 8.3, scan rate of 5 mV s⁻¹, accumulation potential of 0.3 V versus saturated calomel reference electrode (SCE), pre-concentration time of 30 s and potential pulse amplitude of 50 mV. In these experimental conditions, the proposed methodology responds to lithium ions in the concentration range of 2.8×10⁻⁶ to 2.0×10⁻³ mol l⁻¹ with a detection limit of 5.6×10⁻⁷ mol l⁻¹. The determination of the lithium ions content in different samples of natural waters samples using the proposed methodology and atomic absorption spectrophotometry are in agreement at the 95% confidence level and within an acceptable range of error.     

A gas flow proportional detection system for the determination of boron in aerosol samples and other sample types

This work describes the design, fabrication, and testing of a lucite bodied proportional gas detection system for the analysis of boron in selected samples via detection of the charged particles produced in the 10B(n,)⁷Li reaction induced by thermal neutrons. The detector was designed for internal placement of samples; the sample types of major interest were airborne aerosols collected on filters or particulate impaction plates. Samples were irradiated with the detector in the thermal neutron field produced in the graphite thermal column of the University of Lowell's one megawatt research reactor. Determined sensitivities for boron varied from 6.2·10^–8 to 1.73·10^–6 cpm·ng^–1 (n·cm^–2J·s^–1)^–1 depending on the physical characteristics of the samples. For a nominal counting time of ten minutes the lower limit of mass detection of natural boron was determined to be 12.1 nanograms. The analytical method was applied to the estimation of boron in fourteen samples of natural aerosols collected on membrane filters. Analysis of prepared samples and natural aerosol samples by ICP emission showed good agreement with analysis via the (n,) reaction. Application of the method to other sample types was demonstrated by the determination of boron in samples of borosilicate glass and borated polyethylene.     

The Boron and Lithium Content of South African Coals and Coal Ashes

Abstract

Boron and lithium were determined in over a hundred coals and power station ashes by inductively coupled plasma atomic emission spectroscopy. The levels of boron in coals and fly ashes range from 15 to 83 μg.g^?1 and from 23 to 600 μg.g^?1, respectively, while lithium occurred at levels of between 45 and 81μg.g^?1 in coals and 77 and 359μg.g^?1 in fly ashes. Both elements were found to vary considerably between different coals and ashes produced. In most cases the boron concentration was found to increase systematically between the first and last precipitators where smaller particle size fractions are collected. The availability of boron from the leaching of fly ashes by water was investigated. Leachabilities were found to vary for ashes produced at different power stations.     

Development of an on-line isotope dilution laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method for determination of boron in silicon wafers

A method has been developed based on an on-line isotope dilution technique couple with laser ablation/inductively coupled plasma mass spectrometry (LA-ICP-MS), for the determination of boron in p-type silicon wafers. The laser-ablated sample aerosol was mixed on-line with an enriched boron aerosol supplied continuously using a conventional nebulization system. Upon mixing the two aerosol streams, the isotope ratio of boron changed rapidly and was then recorded by the ICP-MS system for subsequent quantification based on the isotope dilution principle. As an on-line solid analysis method, this system accurately quantifies boron concentrations in silicon wafers without the need for an internal or external solid reference standard material. Using this on-line isotope dilution technique, the limit of detection for boron in silicon wafers is 2.8 × 10¹⁵ atoms cm⁻³. The analytical results obtained using this on-line methodology agree well with those obtained using wet chemical digestion methods for the analysis of p-type silicon wafers containing boron concentrations ranging from 1.0 × 10¹⁶ to 9.6 × 10¹⁸ atoms cm⁻³.     

Non-destructive compositional analysis of sol–gel synthesized lithium titanate (Li2TiO3) by particle induced gamma-ray emission and instrumental neutron activation analysis

Lithium titanate, one of the important tritium breeding materials in D–T based fusion reactor under ITER programme, was synthesized through sol–gel route. For chemical quality control of finished product, it was necessary to quantify the lithium and titanium contents. As this ceramic sample is difficult to dissolve, non-destructive analytical methods are preferred for compositional analysis. In the present work, two non-destructive nuclear analytical methods namely particle induced gamma-ray emission (PIGE) using proton beam and instrumental neutron activation analysis (INAA) using reactor neutrons were standardized for the determination of lithium and titanium concentrations, respectively and applied to eleven samples of lithium titanate. To the best of our knowledge, Li quantification in lithium titanate sample is being reported for the first time using PIGE. For quantifications of Li and Ti, 478 keV prompt gamma-ray from ⁷Li (p, p′γ) ⁷Li and 320 keV gamma-ray from ⁵⁰Ti (n,γ) ⁵¹Ti were measured, respectively, by high resolution gamma-ray spectrometry. The PIGE and INAA methods were validated using several synthetic samples containing lithium and titanium, respectively. Concentrations of lithium and titanium and Li/Ti mole ratios were evaluated and compared with the stoichiometric concentration of Li₂TiO₃.     

Determination of isotope ratios of chromium nickel,zinc and copper by gas chromatography-mass spectrometry by using volatile metal chelates

A gas chromatographic-mass spectrometric (GC-MS) method involving thermally stable, volatile chelates was investigated for measurements of isotope ratios of chromium, nickel, zinc and copper. The chelating agents acetylacetone, trifluoroacetylacetone, sodium diethyldithiocarbamate and lithium bis (trifluoroethyl)dithiocarbamate [Li(FDEDTC])] were used. Experimental conditions for the preparation of chelates and the mass spectrometric operating parameters for precise and accurate measurement of isotope ratios were optimized using a general-purpose mass spectrometer. Imprecision values of 1–4% were obtained for measurements of different isotope ratios using chelates containing about 10 ng of metal. The capability of this technique for the accurate determination of natural and altered isotope ratios was also evaluated for these elements using Li(FDEDTC) as a chelating agent. This GC-MS method obviates the need for a more specialized mass spectrometer such as a thermal ionization or inductively coupled plasma mass spectrometer for trace metal determination. The technique gives detection limits down to parts per 10⁹ levels and offers considerable potential for isotope dilution measurements.     

Determination of boron isotopic variations in aquatic systems with negative thermal ionization mass spectrometry as a tracer for anthropogenic influences

A technique for precise boron isotope ratio measurements with a high detection power has been developed by negative thermal ionization mass spectrometry (NTIMS). Relative standard deviations in the range of 0.03–0.3% have been obtained for the determination of the ¹¹B/¹⁰B isotope ratio using nanogram amounts of boron. Ba(OH)₂ has been applied as ionization promoter for the formation of negative thermal ions. By adding MgCl₂ better reproducibilities of the measurement have been achieved. A possible interference of BO^-₂ ions at mass number 42 by CNO^- could be excluded by the sample preparation technique used. Contrary to other NTI techniques no dependence of the measured isotope ratio on the boron amount used has been observed. Anthropogenic and natural saline influences in ground water have been successfully identified by boron isotope ratio determinations with this NTIMS method, due to the different isotopic composition of boron in natural and anthropogenic substances. In sewage, the boron isotope ratio is substantially influenced by washing powder, which contains low ¹¹B/¹⁰B ratios (expressed in ¹¹B values normalized to the standard reference material NIST SRM 951). In contaminated ground water, low ¹¹B values are normally correlated with high boron and high chloride concentrations. On the other hand, ¹¹B shifts to higher values in less contaminated samples. For ground water with saline influences, only the ¹¹B determination, and not the boron or chloride content, allowed the correct identification of this natural source of contamination.     

Über die Bestimmung von Spurenelementen in biologischen Materialien Mit Hilfe der Neutronenaktivierungsanalyse

Neutron activation analysis was used to determine the elements Cu, Mn, As, Cd, Fe, Mo, Zn, Co, Cr, and Se in biological materials. Three different activation analytical techniques were tested by analysing one and the same sample: (1) the instrumental determination, (2) the determination after removal of the major contaminants²⁴Na and³²P, and (3) the determination after radiochemical separation. These three techniques are described and the results obtained are discussed. The detection limits determined for each technique are compared.      

Square‐Wave Voltammetry Determination of Aspartame in Dietary Products Using a Boron‐Doped Diamond Electrode

Abstract

The use of square‐wave voltammetry in conjunction with a cathodically pretreated boron‐doped diamond electrode for the analytical determination of aspartame in dietary products is described. In this determination, the samples were analyzed without previous treatment in a 0.5 mol l^?1 H₂SO₄ solution. A single oxidation peak at a potential of 1.6 V vs. Ag/AgCl (3.0 mol l^?1 KCl) with the characteristics of an irreversible reaction was obtained. The analytical curve was linear in the aspartame concentration range 9.9×10^?6 to 5.2×10^?5 mol l^?1 with a detection limit of 2.3×10^?7 mol l^?1. The relative standard deviation (n=5) obtained was smaller than 0.2% for the 1.0×10^?4 mol l^?1 aspartame solution. The proposed method was applied with success to the determination of aspartame in several dietary products and the results were similar to those obtained using an HPLC method at 95% confidence level.     

Method development for simultaneous multi-element determination of hydride forming elements (As, Bi, Ge, Sb, Se, Sn) and Hg by microwave induced plasma-optical emission spectrometry using integrated continuous-microflow ultrasonic nebulizer-hydride generator sample introduction system

The analytical potential of a coupled continuous-microflow ultrasonic nebulizer dual capillary system (µ-USN/DCS)–Ar/He mixed gas microwave induced plasma-optical emission spectrometry (MIP-OES) has been evaluated for the purpose of determination of hydride forming elements (As, Bi, Ge, Sb, Se, Sn) and a vapor element (Hg). A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. Analytical performance of the ultrasonic nebulization system was characterized by determination of the limits of detection (LODs) and precision (RSDs) with the µ-USN/DCS observed at a 15 µL min^{− 1} flow rate. At flows of ≤ 15 µL min^{− 1}, solvent loading in the plasma is sufficiently low to make desolvation unnecessary. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σ_blank criterion, peak height) were 1.2, 5.4, 6.3, 1.8, 3.3, 2.4 and 3.0 ng mL^{− 1} for As, Bi, Ge, Sb, Se, Sn and Hg, respectively. The method offers relatively good precision (RSD ranged from 8 to 11%) for liquid analysis and microsampling capability. Interference effects by transition metals have been shown to be corrected by the addition of thiourea, as a pre-reducing agent and masking agent. The accuracy of the method was verified using certified reference materials (DOLT-2, GBW 07302, SRM 2710, and SRM 1643e) and by the aqueous standard calibration technique. The measured contents of elements in reference materials were in satisfactory agreement with the certified values.     

Neutron induced radiography in the determination of boron in drinking water

Neutron induced radiography has been applied to the determination of boron concentrations in drinking water, collected from natural springs of Reshian and Muzaffarabad areas of Azad Kashmir, Pakistan, using CR-39 etched track detectors. The technique is based upon the simultaneous irradiation with thermal neutrons of a sample of unknown concentration and a standard of known boron concentration, fixed on a track detector. The subsequent counting of alpha and ⁷Li tracks in the detector resulting from the ¹⁰B(n,)⁷Li nuclear reaction is done after chemical etching. Boron concentration in the sample is determined by comparing ⁷Li and alpha-particle track density with that of a standard of known boron concentration. Boron concentrations in drinking water samples from Muzaffarabad and Reshian area of Azad Kashmir have been found to vary from (0.054±0.001) mg/l to (0.250±0.004) mg/l with an average of (0.16±0.002) mg/l. The observed concentration of boron in drinking water has been found to be less than the provisional Maximum Acceptable Concentration level (0.4 mg//l) of WHO. The drinking water from the reported area has been found to be within safe limits as far as boron related health hazards are concerned.This revised version was published online in November 2005 with corrections to the Cover Date.     

Indirect Determination of Trace Tetraborate by Differential Pulse Polarography Using Its Copper Complex and Application to Waste and Drinking Water

A new differential pulse polarographic (DPP) method has been developed for the trace determination of boron. Its most stable copper complex is used in 0.5 M KNO₃ electrolyte since boron is not electroactive. By continuous addition of tetraborate to copper solution, the copper peak decreased first but then the peak became very small and nearly constant. This point was used for the boron determination. It was found that one mole of copper used two moles of tetraborate. Using this relationship, 1×10^?5 M tetraborate could be determined. The quantification limit was 2.5×10^?6 M and detection limit was 8×10^?7 M. In the presence of complex forming ions such as Pb, Zn, and Cd, the borate found in sample was somewhat smaller because of their reaction with borate. But since their complexes were not as strong as copper, only a few percent of borate were used. No interference was observed in the presence of calcium, chloride and sulfate. This method is applied for the determination of B in borax ore, waste water of borax industries and tap water of Ankara city.     

Speciation and analysis of corrosion products in the primary coolant of pressurized water reactors

The procedure involves separate sampling and determination of the insoluble, cationic and anionic species of corrosion products (Fe, Ni, Cr, Mn, Co, Zn, Cu) in the primary coolant of pressurized water reactors (PWRs) with concentrations in the range 0–2000 mg l^?1 boron and 0–5 mg l^?1 lithium. Samples of coolant (0.2–1 l) are passed through packs consisting of one 0.45-μm filter paper, one cation-exchange membrane (Whatman SA-2) and one anion-exchange membrane (Whatman SB-2). The membranes are examined by wavelength-dispersive x-ray spectrometry. Selection of the ion-exchange membranes and the influence of the boron and lithium concentrations (and pH) on retention of soluble species are discussed. With sample volumes of 0.5 l, the detection limits are between 0.05 and 0.3 μg l^?1 for undissolved species and from 0.03 to 0.14 μg l^?1 for ions. Data collected during a PWR shutdown procedure are summarized.