Determination of nitrogen by neutron activation in meteorites and rocks

The results of determination of nitrogen content in meteorites by neutron activation are reported. The method is based on the¹⁴N(n,p)¹⁴C reaction, which occurs upon irradiation of the samples by neutrons. The use of proportional gas-filled countes for the recording of¹⁴C made it possible to obtain the low nitrogen detection limit of 0.001 g.     

Corrections for carbon and oxygen interference in the 14-MeV neutron activation determination of nitrogen

Reactions in the carbon and oxygen atoms of sample matrix can lead to errors in the 14 MeV neutron activation determination of nitrogen based on the¹⁴N(n, 2n) reaction, particularly as a consequence of proton-induced reactions leading to¹³N formation in samples of an organic nature. In this study, the extent of such interferences have been evaluated by measuring the apparent N contribution when a series of alcohols and a water sample were irradiated with 14 MeV neutrons from a Texas-Nuclear neutron generator under the same conditions used for trace N determination and contributions amounting to from 0.1 to 1% apparent N content observed (and corrected for). Owing to neutron flux in stabilities and assymetries, flux monitoring was done with aluminum foils on either side of the samples for N analysis, and which were counted for²⁴Na. Two samples of foodstuff were analyzed correction for C and O interference, agreed with conventional analysis within ±10%.     

Use of D–T-produced fast neutrons for in vivo body composition analysis: a reference method for nutritional assessment in the elderly

Body composition has become the main outcome of many nutritional intervention studies including osteoporosis, malnutrition, obesity, AIDS, and aging. Traditional indirect body composition methods developed with healthy young adults do not apply to the elderly or diseased. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used to assess in vivo elements characteristic of specific body compartments. Non-bone phosphorus for muscle is measured by the ³¹P(n,)²⁸Al reaction, and nitrogen for protein via the ¹⁴N(n,2n)¹³N fast neutron reaction. Inelastic neutron scattering is used to measure total body carbon and oxygen. Body fat is derived from carbon after correcting for contributions from protein, bone, and glycogen. Carbon-to-oxygen ratio (C/O) is used to measure the distribution of fat and lean tissue in the body and to monitor small changes of lean mass. A sealed, D–T neutron generator is used for the production of fast neutrons. Carbon and oxygen mass and their ratio are measured in vivo at a radiation exposure of less than 0.06 mSv. Gamma-ray spectra are collected using large BGO detectors and analyzed for the 4.43 MeV state of carbon and 6.13 MeV state of oxygen, simultaneously with the irradiation. P and N analysis by delayed fast neutron activation is performed by transferring the patient to a shielded room equipped with an array of NaI(Tl) detectors. A combination of measurements makes possible the assessment of the quality of fat-free mass. The neutron generator system is used to evaluate the efficacy of new treatments, to study mechanisms of lean tissue depletion with aging, and to investigate methods for preserving function and quality of life in the elderly. It is also used as a reference method for the validation of portable instruments of nutritional assessment.     

Determination of boron, carbon, nitrogen and oxygen in nickel by charged particle activation analysis

Summary The determination of boron, carbon, nitrogen and oxygen in nickel by charged particle activation using the reactions ¹⁰B(d, n)¹¹C, ¹²C(d, n)¹³N, ¹⁴N(p, )¹¹C and ¹⁶O(³He, p)¹⁸F is studied. The interference of ¹¹B(p, n)¹¹C with the ¹⁴N(p, )¹¹C reaction is taken into account. ¹¹C, ¹³N and ¹⁸F are separated by oxygen combustion followed by trapping of ¹¹CO₂ in NaOH and by steam distillation of ¹³NH₃ and of H₂Si¹⁸F₆, respectively. The results obtained were 0.129±0.035 g g^–1 for boron, 86.4±8.3 g g^–1 for carbon, 1.077±0.037 g g^–1 for nitrogen and 8.91±1.00 g g^–1 for oxygen. The results for nitrogen and oxygen agreed satisfactorily with those of other analytical methods.Grateful acknowledgement is made to Prof. J. Hoste for his interest shown in this work, to J. Pauwels (B.C.M.N., Geel) for providing the samples, to B. F. Schmitt (Bundesanstalt für Materialprüfung, Berlin) for helpful information concerning the radiochemical separation of ¹¹C and to the NFWO and the IIKW for financial support.     

Oxygen isotope measurement by instrumental neutron activation analysis using reactor neutron—Revisited

The oxygen isotopes¹⁶O and¹⁸O were determined using reactor instrumental neutron activation analysis by utilizing the¹⁶O(n, p)¹⁶N and the¹⁸O(n, )¹⁹O reaction in the UCI 250 kw TRIGA research reactor.¹ Such measurements were used to follow an exchange reaction between H₂ ¹⁸O and finely ground coal. The best conditions for the determination were explored and interference reactions quantified. Single irradiation/count sequences were used to determine 30 parts per thounsand of¹⁶O and 1 part per thousand of¹⁸O in a 400 mg sample of an HVA rank coal to a 25% (1) precision. Reactor pulses were shown to improve these detection limits significantly. Special attention was given to correcting for the high count rates from other induced activites.     

Oxygen and nitrogen in coal by instrumental neutron activation analysis

The feasibility of using fast neutron (14 MeV) activation analysis techniques for the determination of oxygen and nitrogen in coal has been investigated. Conditions that favor instrumental neutron activation analysis (INAA) include the absence of problems associated with sample dissolution and the capability of extremely rapid analyses as compared to older techniques such as the Kjeldahl method for nitrogen. Most previous oxygen determinations have been by difference after major component analyses. In the present study, oxygen was determined in sized coal and its low temperature ash (LTA) with the difference representing the organic oxygen content. Both the oxygen and nitrogen analyses employ a multiscaling technique with the former based on the¹⁶O(n, p)¹⁶N reaction, while the latter utilizes the annihilation radiation produced by the product of the¹⁴N(n, 2n)¹³N reaction. The high-energy gamma-radiation associated with the decay of¹⁶N was essentially free of spectral interferences for coal analysis, although fluorine could cause a primary interference if the F/O ratio exceeds 0.02. In the nitrogen work, experiments were performed to determine correction factors to account for the effects of the¹²C(p, γ)¹³N and¹³C(p, n)¹³N “knock-on” reactions and the³⁹K(n, 2n)³⁸K reaction which produce interfering β⁺ emitting radionuclides. Data are presented for oxygen in Western Kentucky No. 9 and No. 11 coal and coal ash and for nitrogen in eleven different coals.     

Instrumental neutron activation determination of Pt, Ru, Ir, Sc, Cr, Fe, Co, La, Ce, Nd, Sm, Yb, Lu, Hf and Ta employing CIRUS reactor as a thermal neutron source

An accurate and simple method has been developed for the determination of Pt, Ru, Ir and other elements employing instrumental neutron activation analysis (INAA). Nondestructive analysis has been carried out for the determination of these elements in different rock samples such as Dolerite, Dyke Dolerite, Country Basalt, Hyaloclastite, Trachyte, Ijolite, Spillite, Diorite and Lamprophyre from various locations like Daman, Tapti, Murud, Talasari, Ranala and Bassein in Maharashtra state. High flux provided by the CIRUS reactor (1×10¹³ n cm^–2s^–1) has been used for thermal neutron bombardment followed by radioassaying of the (n,) products on a HPGe detector coupled to a PC-based MCA unit.     

Nitrogen determination using the14N/p, α/11C reaction at low energies

Nitrogen determination with the¹⁴N/p, /¹¹C reaction at 6.81 MeV, has been performed in organic compounds. Positron annihilation from¹¹C allowed determination of nitrogen contents as low as 0.35% dried weight. Comparison of these results with those from the standard Kjeldahl method showed a 0.999 linear correlation coefficient.     

Gamma-activation analysis of nitrogen solubility in alumosilicates at high pressure and temperature

A solubility of nitrogen in natural basalts and synthesized albite at 1250 °C and 3 kbar was studied by -activation method based on the reaction¹⁴N(,n)¹³N with radiochemical separation of nitrogen by high-temperature extraction at 1800 °C. Detection limit of 0.2 g in the samples of 15–20 mg weight is obtained. The investigation originated from the study of processes of accumulation and redistribution of nitrogen in rock-forming alumosilicate melt of the Earth mantle. The dependence of nitrogen solubility on the oxygen volatility and pressure were obtained (within 1–3 kbar in the presence of IW buffer [iron(Fe)-wustite(FeO)]) and NNO (Ni–NiO), and essential effect of the composition of the initial matrix was found. Special attention was given to standards, background, interference reactions, reliability and accuracy of the results.     

Determination of nitrogen in pork meat using in-vivo prompt gamma-ray activation technique

The concentration of nitrogen in pork meat is determined by in-vivo prompt gamma-ray activation analysis using the reactor neutron beam and a high purity germanium gamma-ray spectrometer. The photopeak area of the 10827 keV high energy prompt gamma-ray, originated from¹⁴N(n, ) reaction on the pork medium, is analyzed to determine the concentration of nitrogen. Urea solutions with various concentration of nitrogen are used to calibrate the absolute efficiency of the gamma-ray spectrometer. In 9000 s irradiation and counting period, the minimum detectable concentration is 1.7 g of N/100 g of meat using the in-vivo technique. The result is also compared to data obtained by another analytical method. This nondestructive, in-vivo technique, with nominal radiation dose, is a reliable and promising method to determine the nitrogen concentration in living body.     

Spin density distribution in paramagnetic azafullerene

Hyperfine coupling (HFC) constants for ¹⁴N and ¹³C nuclei in azafullerene C₅₉N (1) were calculated. The HFC constants for the ¹H and ¹³C nuclei in the ^·CH₃ radical were calculated as functions of the pyramidal distortion of the angles at the carbon atom. Using this angular dependence, the spin density distribution of the unpaired -electron in 1 was determined. The spin density of the unpaired -electron in 1 is mainly localized around the nitrogen atom.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2372–2374, November, 2004.     

Synthesis of195mPt radiolabelled cis-diamminedichloroplatinum/II/ of high chemical and radiochemical purity using high performance liquid chromatography

An improved method is described for the synthesis of^195mPt-radiolabelled cis-diamminedichloroplatinum/II. An amount of 10 mg of 95% enriched¹⁹⁴Pt was irradiated for 75 h in the hydraulic conveyer of the KUR at a thermal neutron flux of approximately 8.15×10¹³ n.cm^–2.sec^–1 and the^195mPt-radiolabelled CDDP was purified using HPLC. The chemical yield is 61% its chemical purity is greater than 99.74% the radiochemical purity is nearly 100%, and the specific activity is 7.4×10⁶ Bq mg^–1 CDDP/200 Ci mg^–1 CDDP/.     

Determination of 6-amino-2,2-dimethyl-1,3-dioxepan-5-ol by postcolumn derivatization witho-phthalaldehyde/2-mercapto-ethanol after ion-pair chromatography

Summary A high-performance liquid chromatographic method is discribed for the determination of 6-amino-2,2-dimethyl-1,3-dioxepan-5-ol using Spherisorb ODS II stationary phase and mobile phase 30:70 (v/v) methanol: aqueous 1-octane sulfonic acid. Detection was fluorimetric following postcolumn derivatization with o-phthaladehyde/2-mercaptoethanol. The procedure was applied to the analysis of aqueous solutions and microcrystalline suspensions in liquid paraffin, prepared for investigation of the toxicological profile. The method was validated for selectivity, linearity of detector response, repeatability, limit of detection and quantitation. The HPLC method was selective. The instrumental limit of detection was 0.5 ng per injection (0.05 g mL^–1). The method detection limits were 0.5 g mL^–1 aqueous solution and 5 g mL^–1 liquid paraffin suspension, the quantitation limit 0.05 mg mL^–1 aqueous solution and 1.0 mg mL^–1 liquid paraffin. Linearity was within 0.94–47.1 g mL^–1. Intra-assay accuracy accounted for 99–100% in the range 0.05–226 mg mL^–1 aqueous solution, intra-assay precision for 2% (C.V.). For microcrystalline liquid paraffin suspensions with 1 and 250 mg mL^–1 99 and 109% was found for intra-assay accuracy. Intra-assay precision was 5% (C.V.). Reliable results over a wide concentration range can be obtained. The procedure is considered valid for determination of the analyte in aqueous solution or microcrystalline paraffin oil suspensions.     

Non-destructive bone aluminum assay by neutron activation analysis

A non-destructive method based on instrumental neutron activation analysis (INAA) for the assay of aluminum in bone samples is described. The²⁸Al signal obtained upon neutron irradiation includes contributions from both the reaction²⁷Al(n,)²⁸Al and³¹P(n,)²⁸Al. The first reaction is with the thermal neutrons and the second one is with the fast neutrons. The contribution from the³¹P reaction is calculated from the fact that Ca/P ratio in bone mineral is constant and the amount of calcium can be measured from the thermal reaction⁴⁸Ca(n, )⁴⁹Ca. The aluminum values obtained by the INAA procedure agreed within 10% of those obtained by atomic absorption spectrophotometry. With this assay the levels of aluminum in normal bones (<70 g g^–1 apatite) cannot be determined reliably but higher aluminum levles in bone biopsies associated with Al toxicity, e.g. some patients with renal osteodystrophy, can be determined with a precision of ±10%.     

Utilization of deuterium and15N as activable tracers in solid state sciences

The sensitivity in the determination of deuterium and¹⁵N by nuclear reactions was examined for the following reactions: (1)¹⁵N(d,n)¹⁶O (or p+)+(6.13, 7.11 MeV); (2) D(³He,)⁴He (13 MeV); and (3)¹⁵N(,n)¹⁸F. By these activations with suitable etching techniques, sub ppm regions of D and¹⁵N have proved to be measurable with their depth profiles. Some fundamental properties of hydrogen and nitrogen in silicon are under investigation using of these activable tracers.     

Determination of nitrogen in boron carbide by instrumental photon activation analysis

Boron carbide is widely used as industrial material, because of its extreme hardness, and as a neutron absorber. As part of a round-robin exercise leading to certification of a new reference material (ERM-ED102) which was demanded by the industry we analysed nitrogen in boron carbide by inert gas fusion analysis (GFA) and instrumental photon activation analysis (IPAA) using the ¹⁴N(γ,n)¹³N nuclear reaction. The latter approach is the only non-destructive method among all the methods applied. By using photons with energy below the threshold of the ¹²C(γ,n)¹¹C reaction, we hindered activation of matrix and other impurities. A recently installed beam with a very low lateral activating flux gradient enabled us to homogeneously activate sample masses of approximately 1 g. Taking extra precautions, i.e. self-absorption correction and deconvolution of the complex decay curves, we calculated a nitrogen concentration of 2260 ± 100 μg g⁻¹, which is in good agreement with our GFA value of 2303 ± 64 μg g⁻¹. The values are the second and third highest of a rather atypical (non-S-shape) distribution of data of 14 round-robin participants. It is of utmost importance for the certification process that our IPAA value is the only one not produced by inert gas fusion analysis and, therefore, the only one which is not affected by a possible incomplete release of nitrogen from high-melting boron carbide. Figure Twin-Detector system for analyzing spatially extended samples     

Evaluation of New Pharmaceuticals Using In Vivo Neutron Inelastic Scattering and Neutron Activation Analysis

Nutritional status of patients can be evaluated by monitoring changes in body composition, including depletion of protein and muscle, adipose tissue distribution and changes in hydration status, bone or cell mass. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used to assess in vivo elements characteristic of specific body compartments. The fast neutrons are produced with a sealed deuterium-tritium (D-T) neutron generator. This method provides the most direct assessment of body composition. Non-bone phosphorus for muscle is measured by the ³¹P(n,)²⁸Al reaction, and nitrogen for protein via the (n,2n) fast neutron reaction. Inelastic neutron scattering is used for the measurement of total body carbon and oxygen. Carbon is used to derive body fat, after subtracting carbon contributions due to protein, bone and glycogen. Carbon-to-oxygen (C/O) ratio is used to measure distribution of fat and lean tissue in the body and to monitor small changes of lean mass and its quality. In addition to evaluating the efficacy of new treatments, the system is used to study the mechanisms of lean tissue depletion with aging and to investigate methods for preserving function and quality of life in the elderly.     

Fast non-destructive determination of iron and sulphur in coal by means of neutron radiative capture

The possibility of determination of iron and sulphur in large-scale samples of coal /20–50 kg/, based on process /n, /, was evaluated. The spectral lines of the doublet 7631 keV and 7645 keV were used for the determination of iron, while the line at 5421 keV was used for the determination of sulphur. The neutron source was²⁵²Cf /total neutron emission at 2.5×10⁷ s^–1/ located additionally in D₂O moderator. A Ge/Li/ detector was used for gamma radiation detection. The calibration dependencies of the analyzer were linear. In exposure times of up to 1 h, the detection limits of 0.34% and 0.64% and accuracies of 0.25% and 0.4% have been achieved in case of iron and sulphur, respectively.     

Derivative activation analysis of phosphorus at ppb levels in water samples

A neutron activation analysis procedure has been developed for the indirect determination of phosphorus as orthophosphate at ppb levels, via the formation of antimonyl phosphomolybdic acid. The complex is adsorbed on Sephadex G-25 resin and the antimony is estimated through NAA, allowing the determination of phosphorus. The procedure provides an easy method to adopt for the routine determination of phosphorus at 10 ng ml^–1 levels with good precision, in water samples.     

Determination of carbon in thin layers by means of the12C(d,n)13N nuclear reaction using a 2 MeV Van de Graaf accelerator

A nondestructive method for carbon determination in layers of 3–10 m thickness is considered. The method is based on using the¹²C(d, n)¹³N nuclear reaction with simultaneous account of surface contamination by means of the¹²C(d, p)¹³C competitive reaction. The total cross sections for the¹²C(d, n)¹³N reaction were measured from 0.4 to 1.7 MeV. Proton beam annealing was applied with the purpose of lowering surface carbon content. The detection limit of carbon by this method is 0.5 ppm, relative standard deviation is 0.06. Disturbing effects of carbon diffusion and¹³N recoil backs cattering are also taken into account.