Neutron activation analysis for sodium traces in magnesium

When sodium traces are determined in magnesium matrices by neutron activation analysis, the reaction ²⁴Mg(n,p)²⁴Na interferes by simulating spurious sodium concentrations (about 400–500 p.p.m. for usual irradiation positions in the RS 1 water-pool reactor). A preliminary separation of the sodium traces from the bulk of the matrix by electrudeposition on a mercury cathode and recovery in water by amalgam decomposition, prevented the fast-neutron effects. Electrolysis for 4 h gave almost quantitative recovery of sodium (93±5%) and satisfactory decontamination factors for magnesium (1.5 to 5. 10³). The method is limited by the blank correction (14 μg Na with a glass electrolysis cell). Some results for magnesium samples with both destructive and non-destructive techniques are reported.     

High precision instrumental neutron activation analysis of Sn in cassiterite with the aid of an227Ac−Be isotopic neutron source

A non-destructive method has been developed for the precise and accurate determination of Sn in cassiterite ores. Irradiation is performed by means of a 6.6 Ci²²⁷Ac−BE isotopic neutron source with a total neutron output of 10⁸ n·sec⁻¹. Samples are pellets pressed from a mixture of cassiterite powder and wax as a binding material. With a 4 hrs analysis time and a relative precision of 0.45%, the new method is faster and at least as precise as any existing destructive chemical method. The accuracy is proved to be better than that of the commonly used iodimetric titration method.     

Determination of fluorine in coral skeletons by instrumental neutron activation analysis

Summary A systematic and non-destructive technique is proposed for the determination of fluorine in coral samples by instrumental neutron activation analysis using the ¹⁹F(n,γ)²⁰F reaction. About 50 to 80-mg samples in polypropylene capsules were irradiated for 15 seconds in the pneumatic transfer tube system (PN-3) of JRR-3M reactor. After the irradiation at a thermal neutron flux of 1.5 ^. 10¹³ n ^. cm^{-2 .} s^-1, the coral samples and standards were cooled for 6 seconds and the g-rays emitted were measured for 15 seconds with a Ge detector. The sequence from sample irradiation to g-ray counting was performed under a computer-control mode. The analytical precision was ~5% for the JCp-1 coral standard. The present method was applied to the determination of fluorine in corals from Thailand, Okinawa and the Philippines. The advantage of one method over destructive techniques is discussed by comparing the analytical results obtained for the JCp-1 coral standard using INAA, ion chromatography and spectrophotometry. Factors that may control the levels of fluorine in corals are also discussed.     

Determination of trace impurities in rhodium metal by destructive and non-destructive neutron activation analysis

Trace amounts of Ir, Au, Cu, Pd and Pt were determined in rhodium metal by instrumental neutron activation analysis with Ge(Li) spectrometry as well as by the radiochemical version of the method. The latter was based on a specially developed procedure of the dissolution of Rh, followed by group separation with the aid of ion exchange chromatography. The results obtained by destructive and non-destructive methods are critically discussed and compared. Special attention was paid to self-shielding effect and an accurate method of the correction of this effect is presented.     

The simultaneous determination of As,Cd, Co,Hg, Mo,and Zn in fresh water by neutron activation analysis

A radiochemical neutron activation method for the simultaneous determination of arsenic, cadmium, cobalt, mercury, molybdenum, and zinc in fresh water is described. The method is based on anion-exchange separation in hydrochloric acid media followed by simple precipitations. The determination limits, based on analysis of a 5-ml sample without preconcentration, and with a well-type NaI(Tl) detector, are as follows: As, 10^-3 μg l^-1 ; Cd, 6 × 10^-2 μg l^-1 ; Co, 4 × 10^-3 μg l^-1 ; Hg, 7 × 10^-3 μg l^-1 ; Mo, 10^-1 μg l^-1 ; Zn, 2 × 10^-1 μg l^-1. The method is adequate for the analysis of natural fresh waters.     

Extraction of cesium and strontium into nitrobenzene in the presence of arsenic acid—catechol complex

Quantitative analysis of traces of Pd in a Cu matrix using X-ray fluorescence induced by protons in the MeV range is explained. The method is used for necroanalysis of small portions (20 μg) of a sample in which local inhomogeneity of Pd concentration is found. The sensitivity of the technique may reach 5 ppm (quantitative) for one hour of bombardment of metallic samples. This sensitivity of 5 ppm of Pd in 20 μg of material corresponds to 10^?11 g of Pd effectively detected. The method is rapid (15 min for the determination of 100 ppm of Pd in a Cu matrix with an accuracy of 5%), non-destructive and does not produce any residual activity. Comparative results obtained by other macrotechniques are given.     

Determination of gold by neutron activation analysis in some selected precambrian rocks from Eastern India

Gold was determined in some selected rock samples by neutron activation analysis. The analysis was carried out both in destructive and non-destructive ways followed by γ-ray spectrometry. The amounts of gold that were determined in the respective rock samples varied in the range 10⁻⁴–10⁻⁶%. Besides gold, some other trace constituents such as As, Ag, Sb, W, Se, La, Sm, etc. were also detected and their approximate order of occurrence was determined.     

Determination of cobalt in plant digests by adsorption stripping voltammetry

The procedure involves adsorption of cobalt onto a static mercury drop as its dimethylgloximate complex (pH 9.3, adsorption potential ?0.70 V, adsorption time 2 min), followed by a d.c. cathodic scan, effecting reduction at ?1.15 V (SCE). Of the dominant electroactive trace elements in plants (Mn, Fe, Zn), only zinc interfered; it was masked by nitrolotriacetic acid (2 × 10^?4 M). The detection limit is 0.01 μg l^?1 cobalt in the digest; the relative standard deviation is 2.5% at 0.75 μg l^?1. Calibration is linear in the range 0–6.0 μg l^?1 cobalt. Results obtained by the voltammetric method, by electrothermal atomic absorption spectrometry and neutron activation analysis are compared for seven pasture samples containing 0.1–0.2 mg kg ^?1 cobalt. The activation method provides validation for the same preparation and voltammetric results.     

Rhodium as permanent modifier for atomization of lead from biological fluids using tungsten filament electrothermal atomic absorption spectrometry

Rhodium (Rh) was investigated as a permanent modifier for the atomization of Pb from biological fluids in W-filament atomic absorption spectrometry (AAS). Heating the W-filament with a Rh solution provided a protective coating for subsequent determinations of Pb in blood and urine matrices. The W-filament AAS instrumentation used was based on a prototype design that utilized self-reversal background correction scheme and peak area measurements. We found that Rh not only stabilized Pb during the pyrolysis step, but also facilitated the removal of carbonaceous residues during the cleaning step, requiring much less power than with phosphate modifier. Thus, the filament lifetime was greatly extended to over 300 firings. Periodic reconditioning with Rh was necessary every 30 firings or so. Conditioning the filament with Rh also permitted direct calibration using simple aqueous Pb standards. The method detection limit for blood Pb was approximately 1.5 μg dl⁻¹, similar to that reported previously. Potential interferences from concomitants such as Na, K, Ca and Mg were evaluated. Accuracy was verified using lead reference materials from the National Institute of Standards and Technology and the New York State Department of Health. Blood lead results below 40 μg dl⁻¹ were within ±1 μg dl⁻¹ of certified values, and within ±10% above 40 μg dl⁻¹; within-run precision was ±10% or better. Additional validation was reported using proficiency test materials and human blood specimens. All blood lead results were within the acceptable limits established by regulatory authorities in the US. When measuring Pb in urine, sensitivity was reduced and matrix-matched calibration became necessary. The method of detection limit was 27 μg l⁻¹ for urine Pb. Urine lead results were also validated using an acceptable range comparable to that established for blood lead by US regulatory agencies.     

Neutron activation analysis of microgram amounts of thorium in uranium ores and process liquors by means of thorium-233

A method is described for neutron activation analysis of thorium by employing thorium-233. Decontamination steps include anion exchange in 12.5 N HCL, precipitation of fluoride, extraction with mesityl oxide and thorium oxalate precipitation. The time spent is less than 1 h; spurious activities in counting samples amount only to 2% and can easily be corrected for. The sensitivity of the method is ca. 0.02 μg of thorium in a neutron flux of 10¹²n/cm²/sec with an irradiation time of 5 min.     

The preparation of carrier-free102Rh and102m Rh

Long-lived rhodium radionuclides were produced by the following reactions:¹⁰³Rh(n, 2n)^102(m)Rh;¹⁰³Rh(γ,xn)¹⁰⁰Rh,¹⁰¹Rh,^102(m)Rh;¹⁰⁴Pd(d, α)^102(m)Rh; Ru(d, n)⁹⁹Rh,^101(m)Rh,^102(m)Rh; and . The average cross-section of the¹⁰³Rh(n, 2n)¹⁰²Rh reaction in a fission neutron spectrum is about 0.75 mb. Irradiation of rhodium in the bremsstrahlung spectrum of 50 MeV electrons yielded a¹⁰²Rh activity of 0.11 μCi/g after 3 days at a power of 2 kW. The thick target yield of the reaction¹⁰⁴Pd(d, α)¹⁰²Rh was 0.002 μCi/μAh for 12 MeV deuterons. The thick target yield of the reaction Ru(d,xn)¹⁰²Rh was 0.05 μCi/μAh for 12 MeV deuterons and 4.8 μCi/μAh for 18 MeV deuterons. The best yield was obtained by deuteron bombardment of ruthenium. The chemical separation of carrier-free Rh radionuclides from deuteron-irradiated ruthenium is described, with a chemical yield better than 90%. The same procedure has also been applied for the isolation of¹⁰⁵Rh from neutron-irradiated ruthenium. γ-Ray spectra of⁹⁹Rh,^101(m)Rh and^102(m)Rh from deuteron-irradiated ruthenium and of¹⁰⁵Rh from neutron-irradiated ruthenium, taken with a Ge(Li) detector, are shown; a number of γ-rays, not reported in the literature, were observed. The γ-ray energies were determined with a precision of ca. 0.3–0.4 keV.     

Determination of gold by neutron activation analysis in some selected rocks and plants and its bearing on the genesis of auriferous quartz veins in Singhbhum district,Bihar, Eastern India

Present investigation deals with neutron activation analysis of gold in some varieties of geological samples related to auriferous quartz veins. A few plant specimens of the area were also analyzed. The gold contents in the rock samples as determined by the destructive way of analysis vary in the range 10⁻⁵ to 10⁻⁷%. In case of plant samples, however, the non-destructive method of analysis of the plant ashes was followed and the concentration of gold was found to be of the order of 10⁻⁵%. In plants, besides gold, some associated elements, such as La, Ce, Sm, Lu, Zr, Hf, Se, W, As and Sb were also identified.     

Rapid non-destructive determination of thin films of platinum by particle back-scattering

Rutherford back-scattering of α-particles is used to determine trace amounts of thin films of platinum. The method is sensitive to 0.3 ng of platinum and the response is linear from at least 0.01 to 80 μg Pt cm^-2 of substrate surface area. Calibration with weighed standards reveals good accuracy and precision throughout the linear range. Up to at least 80 μg cm^-2, no matrix effects can be observed for platinum determinations on Mylar, carbon, glass, and glass or quartz coated with up to 0.5 μm thicknesses of tin oxide. Particle-induced x-ray emission spectra are included to show their utility in surface composition analysis. The analytical procedure for the determination of platinum is rapid and non-destructive, and requires minimal sample preparation.     

Uranium in coral skeletons determined by epithermal neutron activation analysis

A simple and non-destructive method has been proposed for the routine determination of uranium by epithermal neutron activation analysis in coral skeletons. Using a cadmium capsule, about 0.1-0.2 g samples were irradiated for 6 hours in the Triga Mark II Reactor. Measurements of -ray (²³⁹Np via ²³⁹U) were performed with each sample and standard after cooling for about three days. Compared with a non-destructive thermal NAA, the present method was found to improve the sensitivity because it reduced the intense Compton background induced by ²⁴Na. We determined uranium in coral standards within 2% of analytical precision. The data obtained for the carbonate standards are mostly consistent with reported values. The present method could be usefully applied to determine uranium contents in fossil corals from the Funafuti Atoll in the Pacific. The distribution of uranium between seawater and coral skeletons is also discussed in order to understand the environmental media in which the coral grew.     

Non-destructive neutron activation determination of silver and antimony in bismuth byγ.γ-coincidence spectrometry

A non-destructive neutron activation method was developed for the determination of silver and antimony in high-purity bismuth ; γ,γ-coincidence counting of ^110mAg or ¹²⁴Sb was applied. The activity of the matrix or other impurities did not interfere. When 1-g samples were irradiated at a neutron flux of 4·10¹¹ n cm^-2 sec^-1 for 25 days, the sensitivity of the method was in the p.p.b. region.     

Halogen speciation in the rat thyroid: Simultaneous determination of bromine and iodine by short-term INAA

The study describes a mode of non-destructive simultaneous determination of bromine and iodine concentrations, by reactor instrumental neutron activation analysis (INAA) in the regime of short-term activation. Under the conditions of 1-minute activation in the neutron flux of 8.0·10¹³ n·cm⁻²·s⁻¹, it was possible to determine reliably as little as 5·10⁻⁸ g bromine and about 10⁻⁷ g iodine in matrices of a given type and of the mass of about 5 mg dry weight. We applied this method for the determination of Br and I concentrations in the whole rat thyroid gland as well as for the halogen speciation in fractions separated from this organ.     

Combining Ammonium Pyrrolidine Dithiocarbamate/methyl Isobutyl Ketone Microextraction in an Inexpensive Disposable Pipette with Laser Ablation Inductively Coupled Plasma Mass Spectrometry for the Determination of Cd and Pd

This paper describes a new analytical method, using a combination of ammonium pyrrolidine dithiocarbamate/methyl isobutyl ketone (APDC‐MIBK) microextraction and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS), for the determination of the concentrations of Cd and Pb in aqueous samples. Only 200 μL of organic solvent was used throughout the entire analysis process, with enhancement factors as high as 25. Recoveries from replicate analyses of natural water [NIST 1640(a)] containing mean concentrations of 3.1 μg Cd L^?1 and 9.3 μg Pb L^?1 were 95 ± 3 and 104 ± 4%, respectively. The corresponding detection limits were 0.6 μg L ^?1 for Cd and 0.9 μg L ^?1 for Pb. The main advantage of this approach is its simplicity in terms of sample preparation, as demonstrated by quantifying the levels of Cd and Pd in real samples, including tap water, groundwater, and seawater, using a standard addition method.     

Transition metal methylene complexes : III. Methylene (CH2), a carbonyl analogous ligand; crystal structure of μ-methylenebis(carbonyl-η5-cyclopentadienylrhodium)(Rh—Rh

μ-Carbonylbis(carbonyl-ν⁵-cycopentadienylrhodium)(Rh—Rh) reacts with N-methyl-and N-ethyl-N-nitrosourea in boiling benzene to yield the dinuclear, diamagnetic, neutral rhodium complexes μ-methylene- (A) and μ-ethylidenebis(carbonyl-η⁵-cyclopentadienylrhodium)(Rh—Rh) (B), respectively. Deuterium labelled experiments prove the origin of the metal-stabilized methylene ligand to be the alkyl group of the organic precursor. This new method of preparation of transition metal—methylene complexes may be used as an alternative to the commonly used diazo method; the latter method was shown to work with diazodiethylmalonate and dicarbonyl-η⁵-cyclopentadienylrhodium, the reaction yielding μ-bis(ethoxycarbonyl)methylenebis(carbonyl-η⁵-cyclopentadienylrhodium)(Rh—Rh).Compound A crystallizes in the triclinic system, P$\text{1}$, and with cell constants of a 803.42(5), b 909.98(6), c 938.81(2) pm, α 74.402(3), β81.923(3), and γ 83.685(6)°. The unit cell volume and the calculated density are 651.6 ų and 2.069 g cm^-3, for one molecule in the asymmetric unit. The molecular geometry of μ-CH₂[η⁵-C₅H₅Rh(CO)]₂ was established from 2718 unique reflections collected with a computer-controlled diffractometer and refined to a final R(F) = 0.0379. The molecular parameters derived from the single-crystal X-ray study conform to a remarkable degree with those found for μ-CO[η⁵-C₅H₅Rh(CO)]₂. Thus, the bridging ligands CH₂ and CO seem to be analogous in their effects on the structural characteristics of the molecular framework of the two molecules.     

Non-destructive proton activation analysis for nitrogen in refractory metals

The non-destructive determination of nitrogen in some refractory metals was studied by activation analysis with the ¹⁴N(p, n)¹⁴O reaction. The samples were irradiated with 12-MeV protons from a cyclotron. The proton beam intensity was normalized by means of a copper flux monitor. After chemical etching, the ¹⁴O activity (E_γ = 2313 keV, T_{$\text{1}\text{2}$} = 70.5 s) of the sample was measured by means of a Ge(Li) or NaI(Tl) detector. Standardization was carried out by the “average cross-section” method with nylon 6 as a nitrogen standard. The method gives a sensitivity of 0.4–30 μg g^?1 for analysis of Ta, W, Nb, and Ti, and 2000–4000 μg g^?1 for Zr, Ni and Mo.     

Design and evaluation of a TNA explosive-detection system to screen carry-on luggage

Thermal neutron analysis (TNA) technology has been used for the non-destructive detection of explosives. The system uses a relatively weak ²⁵²Cf neutron source (1.03·10⁷ n/s) and two 3"×3" NaI(Tl) detectors. The presence of explosives is confirmed via detection of the 10.83 MeV prompt gamma-ray associated with nitrogen decay. The MCNP4A code was used to simulate the neutron and gamma transport through the system. The thermal neutron flux in the activation position was measured using gold and indium foils. The measured thermal neutron flux was lower, by not more than 9.5%, than that of simulation. In this report the results of the preliminary tests on the system are described.