Radiochemical proton activation analysis for the determination of cadmium and lead in sediment reference materials

Proton activation analysis was used for the determination of cadmium and lead in three sediment reference materials. The method is based on the^111,112Cd(p, xn)¹¹¹ In and the^206,207,208Pb(p, xn)²⁰⁶Bi reactions.¹¹¹In and²⁰⁶Bi were chemically separated by anion exchange. The results obtained were taken into account for the certification of the materials and are in the excellent agreement with the certified values.     

Non-destructive determination of plutonium in nuclear fuel rods and pellets

Analytical and Bioanalytical Chemistry - A non-destructive method and an experimental set-up are described by which the Pu content in UO2/PuO2 mixed oxide (MOX) pellets and in fuel rods,...     

Method Development for the Speciation of Chromium in River and Industrial Wastewater Using GFAAS

A simple, sensitive and inexpensive method for the speciation of Cr(VI) and Cr(III) in river and industrial wastewater was developed, optimized and validated. Samples were collected, filtered and then chromium species were determined in the filtrate. In the filtrate, total Cr was determined directly by Graphite Furnace Atomic Absorption Spectrometry (GFAAS). A portion of the filtered sample was buffered to pH 6.4, extracted with Amberlite LA-2/MIBK and finally Cr(VI) was determined in the organic extract and Cr(III) in the aqueous phase using GFAAS. The method was evaluated by analysis of the certified reference material, CRM 544, and good accuracy was obtained. The limit of detection for Cr(VI) and Cr(tot)/Cr(III) was found to be 0.30 and 0.08 µg L⁻¹, respectively, and a precision expressed as relative standard deviation of better than 11% was achieved for nine replicates. A number of water samples from the Tinishu Akaki River, Ethiopia, and wastewater samples from a chemical plant in Germany, were analysed. In addition to the GFAAS method, Cr(tot) was also determined using ICP-MS (in CRM 544, lyophilized water, and Tinishu Akaki River water samples) and Cr(tot) and Cr(VI) using UV-VIS spectrophotometry (in CRM 544 and industrial wastewater samples). Good agreement between the different methods was found.     

Determination of lead in atmospheric particulates by flameless atomic absorption spectrometry with a graphite tube

A procedure for the determination of atmospheric particulate lead by flameless atomic absorption spectrometry is described. Aerosols are collected on 10-cm Whatman 41 filters with high-volume pumps. The lead is removed from a one-eighth sector of the filter by two ultrasonic treatments in 0.1 M nitric acid for 10 and 5 min, respectively. Investigations, including comparison with samples pre-ashed at low temperature, indicated that the lead was completely recovered. Routinely 20-μ1 amounts of the solution are injected into a graphite tube and the % absorption at 283.3 nm is measured. The elements normally encountered in atmospheric aerosols do not interfere. The sensitivity for 24-h samples is 0.01 μg m^?3 of air. Sampling time can be reduced to a few minutes in urban air when a larger segment of the filter is used and a larger volume is injected. The reproducibility of the complete procedure is 3% for a typical lead concentration of 0.35 μg m^?3. The method was applied to short-period variations of the lead concentration in urban air.     

Selection of short-lived isotopes for activation analysis with respect to sensitivity

During the last decade the use of short-lived isotopes in activation analysis has exploded, owing to the application of high resolution gamma-ray spectrometry. Complex spectra can in fact be resolved without the need for chemical separations. The application of cyclic activation-counting enables the use of isotopes with half-lives below 10 seconds. These short-lived isotopes can be produced by different activation processes. As neutron sources one can distinguish reactors, generators for 14 MeV or high energy machines such as cyclotrons and isotopic neutron sources. High energy photons can be produced by interaction of an energetic electron beam with a target, giving rise to an intense bremsstrahlung spectrum with maximum energy from 10 up to 70 MeV. While these photons induce several types of threshold reactions, lower energetic photons are used for resonance activation producing metastable isomers. More and more also charged particles (p, d,³He, α) are being used as projectiles to produce radioactive isotopes that can be measured in activation analysis. In the present paper a concise compilation is made of the nuclear reactions, applicable in activation analysis of minor or trace constituents using gamma emitting isotopes with half-lived smaller than 1 hour. Activations of all naturally occurring elements, except the noble gases, with Z values ranging from 9 to 92 have been considered. The reactions resulting in the most sensitive gammaspectroscopic determinations have been selected and are tabulated per element, together with the appropriate cross section and the resonance integral if significant for neutron reactions, the cross section at the giant resonance energy for the photon and at the maximum of the excitation function for the charged particle reactions and the threshold energy for all threshold reactions. For each isotope produced the half-life and the major gamma-ray energy is given. Finally calculated or experimental sensitivities have been compiled from a number of references, as the emission rate per second of the most intense gamma-ray, at the end of a 1 minute irradiation under well-defined circumstances for 1 microgram of the element. When cyclic activation has been applied it is indicated. These data are provided for more than 200 nuclear reactions. It appears that the majority of the 70 elements constacred can in some way be determined with a high sensitivity after such a short irradiation. Only for the elements Tm and Tb no reaction yielding a short-lived isotope with a reasonable sensitivity could be found. Both elements can however very sensitively be determined after a longer neutron irradiation. For a number of elements activation analysis by means of the middle-long-lived isotopes (2 hours to 3 days) is the most sensitive even after a 1 minute irradiation and immediate count (Mn, Ga, As, Sr, Ru, La, Eu, Ho, Lu, Os and Au). But for all other elements the highest gamma emission rate results from isotopes with half-lives shorter than 1 hour. Extremely high counting rates are obtained after thermal reactor neutron activation for Na, Sc, V, Co, Se, Rh, Ag, In, Eu, Dy, Er and Hf. For a number of elements the selectivity of the analysis can however largely be enhanced by irradiation under Cd-cover. High σ₀ ratios exist in fact for activation of medium and high Z elements such as Nb, Rb, Rh, Sn, Sb, Ba, Ce, Lu, Ta, Os, Hg and U. For some elements activation with reactor fission neutrons or 14 MeV neutrons provides an interesting sensitivity for a threshold reaction or the production of an isomer (F, Si, P, Cl, Ca, Cr, Se, Y, Ba, Ce, Pr, Bi, Pb). Cyclic activation and counting of very short-lived isotopes has been applied advantageously in the ng to μg range for a number of elements. Also cyclic activation with a 14 MeV generator has recently been studied. Low energy photon activation analysis allows selective production of metastable isomers of Se, Br, Ag, Er, Hf, Ir and Au, while high energetic photon production analysis yields high specific activities for elements such as K, Cr, Se, Br, Mo, Pr, Nd, Ho and allows interesting determinations of Mg, Cl, Si, Cr, Fe, Zr and Pb. Also charged particle activation can be used with surprisingly high sensitivity for some medium and high Z elements (Cr, Y, Se, Br, Zr, Mo, La, Ta, V). The intensity of the irradiation is in these cases mostly only limited by the properties of the sample itself, such as heat transfer and matrix activity. Examples of the compilation will be discussed and applications shown.     

Investigation of HfO(+) interference in the determination of platinum in a catalytic converter (cordierite) by inductively coupled plasma mass spectrometry

The determination of Pt in cordierite is subject to strong interference by spectral overlap from HfO(+) ions with all Pt isotopes. Two mathematical correction methods based on the HfO(+)Hf(+) ratio and a method for the chemical separation of Hf based on adsorption chromatography and isotope dilution were investigated to correct for this interference. Flow infection was used to prevent clogging of the cone orifice. To enhance the sensitivity and thus lower the detection limit, thermospray nebulization was used for sample introduction and the method was compared with pneumatic nebulization. In addition, the memory effects were evaulated for both systems. Analysis of artificial solutions (1 ng Pt ml(-1)) yielded results within 3% of the true value. Th Pt content (ca. 50 ng g(-1)) of a cordierite sample, previously exposed to exhaust gases, could be determined with precisions of about 10-25% and the results agreed with earlier determinations by other workers.     

Determination of strontium in human serum by inductively coupled plasma mass spectrometry and neutron activation analysis: A comparison

Strontium has been determined in a human serum reference material by ICP-MS and by NAA. By ICP-MS, results for (88)Sr and (86)Sr in both 10- and 5-fold diluted serum were in good agreement. For (88)Sr the precision was better than 3% and the detection limit was 0.05 mug/l. under the conditions used. The results were 25.5 mug/l. in the liquid serum or 0.281 mug/g in the lyophilized reference material. In the NAA the (87m)Sr produced was radiochemically separated by extraction with oxine in chloroform. The precision was about 10% and the detection limit 0.02-0.05 mug/g.     

Neutron activation analysis of high purity Selenium: Determination of Bromine

Neutron activation analysis for 2–0.8 p.p.m. bromine in selenium was performed by irradiating i-g samples for 2 h at a neutron flux of 4.10¹¹ n/cm²/sec. The bromine was separated by a double precipitation technique as silver bromide to obtain adequate decontamination and the isotope ⁸²Br (T_{$\text{1}\text{2}$}=35.87 h) measured. Errors due to self-shielding in the standards and flux-depression in the selenium were calculated. Measurements on 2 different photopeaks were made to avoid errors from interfering isotopes.