Vacuum Ultraviolet and Soft X‐ray Photoelectron Spectroscopy of Liquid Beams Using a Hemispherical Photoelectron Spectrometer with a Multistage Differential Pumping System

We present photoelectron spectroscopy of liquid beams using a high‐resolution hemispherical photoelectron spectrometer with a multistage differential pumping system developed in our laboratory. Intense soft X‐ray synchrotron radiation (500‐1200 eV) at SPring‐8 and a relatively large detection solid angle (1.5 × 10^?2 π sr) of the spectrometer enable highly efficient measurements of X‐ray photoelectron spectra of liquids. Vacuum ultraviolet photoelectron spectroscopy using the same spectrometer provides sufficiently high spectral resolution to resolve rotational isomers of gas‐phase molecules.     

Simultaneous δ15N, δ13C and δ34S measurements of low‐biomass samples using a technically advanced high sensitivity elemental analyzer connected to an isotope ratio mass spectrometer

Conventional simultaneous CNS stable isotope abundance measurements of solid samples usually require high sample amounts, up to 1 mg carbon, to achieve exact analytical results. This rarely used application is often impaired by high C:S element ratios when organic samples are analyzed and problems such as incomplete conversion into sulphur dioxide occur during analysis. We introduce, as a technical innovation, a high sensitivity elemental analyzer coupled to a conventional isotope ratio mass spectrometer, with which CNS‐stable isotope ratios can be determined simultaneously in samples with low carbon content (<40 µg C corresponding to ～100 µg dry weight). The system includes downsized reactors, a temperature program‐controlled gas chromatography (GC) column and a cryogenic trap to collect small amounts of sulphur dioxide. This modified application allows for highly sensitive measurements in a fully automated operation with standard deviations better than ±0.47‰ for δ¹⁵N and δ³⁴S and ±0.12‰ for δ¹³C (n = 127). Samples collected from one sampling site in a Baltic fjord within a short time period were measured with the new system to get a first impression of triple stable isotope signatures. The results confirm the potential of using δ³⁴S as a stable isotope tracer in combination with δ¹⁵N and δ¹³C measurements to improve discrimination of food sources in aquatic food webs. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of trace impurities in aluminum nitride by direct solid sampling graphite furnace atomic absorption spectrometry

The trace impurities Cr, Cu, Fe, K, Mn, Sb and Zn were determined in powdered aluminum nitride by direct solid sampling graphite furnace atomic absorption spectrometry using a ZEEnit 60 atomic absorption spectrometer. This spectrometer features inverse Zeeman-effect background correction and a variable magnetic field enabling measurements in two sensitivity modes over a concentration range of three orders of magnitude. The measurement sensitivity can be adjusted to the analyte concentration in the sample. The use of chemical modifiers was not necessary. Calibration was carried out by means of calibration curves obtained with aqueous standard solutions. Accuracy was checked mainly by comparison of the results with those obtained by instrumental and radiochemical neutron activation analysis whereby, excluding the results for potassium, no significant differences were found by carrying out the t-test at the significance level 0.05. The limits of detection were between 0.05 ng g⁻¹ (Zn) and 80 ng g⁻¹ (Fe) and the relative standard deviations below 11 %. With the proposed method, up to ten measurement cycles can be carried out in one hour.     

Characteristics of formvar films used to prevent alpha-detector contamination

Alpha spectrometry is an extremely useful and sensitive for detection of alpha-emitting nuclides. Contamination of the silicon detectors for low-level alpha spectrometry by recoil nuclides is a serious problem in the measurement of alpha emitters decaying to daughter nuclides with short half-lives. This unwanted contamination leads to decreased measurement sensitivity causing a degradation of the limit of detection. The simplest method to prevent this radioactive contamination of detector is to use a catcher film between the alpha source and the detector. In this work we describe the obtaining of the thin formvar films as stopper foils for recoil nuclei and we investigated the influence of these films on alpha spectrometry parameters, as energy shift (~30 keV) and resolution (~7%). No significant deterioration of the alpha spectrometry parameters was observed when using thin formvar films. Using the ASTAR web databases, which calculate stopping powers for alpha particles, the thickness of formvar films was estimated to be about 5.355 × 10⁻⁵ g/cm². The measurements were performed with an ORTEC SOLOIST alpha spectrometer with PIPS detector.     

Determination of the distribution coefficients for134Cs,60Co and234Th in the Pinheiros River sediment-water

We have investigated the possibility of determining the relative concentrations of two radon isotopes (²²²Rn and²²⁰Rn) in the air, using solid state nuclear track detectors (CR-39) as alpha spectrometers. The detectors were exposed to²²²Rn and its daughters and²²⁰Rn and its daughters in the air. Analyzing only roundish tracks, it was observed that the performance of CR-39 as alpha spectrometer varies with etching time, improving markedly for long etching times.     

Direct determination of lead in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) after furnace-fusion in the sample cuvette-tungsten boat furnace

The newly conceived electrothermal vaporization (ETV) system using a tungsten boat furnace (TBF) sample cuvette was designed for the direct analysis of solid samples with detection by inductively coupled plasma mass spectrometry (ICP-MS). Into this small sample cuvette, a solid mixture of the biological samples and diammonium hydrogenphosphate powder as a fusion flux was placed and situated on a TBF. Tetramethylammonium hydroxide solution was added to the mixture. After the on-furnace digestion had been completed, the analyte in the cuvette was vaporized and introduced into the ICP mass spectrometer. The solid samples were analyzed by using a calibration curve prepared from the aqueous standard solutions. The detection limit was estimated to be 5.1 pg of lead, which corresponds to 10.2 ng g^–1 of lead in solid samples when a prepared sample amount of 1.0 mg was applied. The relative standard deviation for 8 replicate measurements obtained with 100 pg of lead was calculated to be 6.5%. The analytical results for various biological samples are described.     

Th isotope measurements of femtogram quantities for U-series dating using multi ion counting (MIC) MC-ICPMS

Results of Th isotope measurements on Harwell Uraninite (HU) solution aliquots and carbonates such as corals and speleothems using multi ion counter (MIC) procedures are presented. A multi ion counter array available for the ThermoFinnigan Neptune multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS) is used for simultaneous measurements of ²³⁰Th and ²²⁹Th ion beams. A static collection of low-level ion beams improves the efficiency of isotope measurements which in turn reduces the required sample size and measurement time. The static measurement also circumvents problems with ion beam intensity fluctuations often observed with a plasma source. Instrumental bias corrections are based on a sample bracketing in-house Th standard solution. The accuracy and precision of the MIC array procedures for ²³⁰Th/²²⁹Th measurements are investigated by comparison to a MC-ICPMS peak jump procedure using just a single ion counting channel. The results show that similar precisions for ²³⁰Th/²²⁹Th measurements can be achieved using the MIC procedure with less than half total ²³⁰Th consumed compared to a peak jump routine. Thus, the MIC setup allows to use less than half the sample sizes for ²³⁰Th/U dating of carbonates compared to peak jump methods enabling higher spatial resolution sampling.     

Quantitative determination of sodium perborate and sodium percarbonate in detergent powders by infrared spectrometry

Sodium perborate (SPB) and sodium percarbonate (SPC) are solid compounds which act as sources of H₂O₂ in solution for stain bleaching, being considered as oxidizing agents in washing powder. This research deals with the quantitative determination of SPB and SPC by an analytical procedure based on attenuated total reflectance Fourier transform infrared spectrometry, utilizing partial least squares for data processing in the 1600-800 cm⁻¹ spectral region. The statistical parameters such as R ², standard error of prediction and relative standard deviation have been evaluated, while number of factors, number of scans and resolution were optimized. The standard deviation of method was 0.006 and 0.010 for SPC and SPB, respectively.     

Nitrogen isotopic analyses by isotope-ratio-monitoring gas chromatography / mass spectrometry

Amino acids containing natural-abundance levels of ¹⁵N were derivatized and analyzed isotopically using a technique in which individual compounds are separated by gas chromatography, combusted on-line, and the product stream sent directly to an isotope-ratio mass spectrometer. For samples of N₂ gas, standard deviations of ratio measurement were better than 0.1‰ (Units for δ are parts per thousand or per million (‰).) for samples larger than 400 pmol and better than 0.5‰ for samples larger than 25 pmol (0.1‰ ¹⁵N is equivalent to 0.00004 atom % ¹⁵N). Results duplicated those of conventional, batchwise analyses to within 0.05‰. For combustion of organic compounds yielding CO₂/N₂ ratios between 14 and 28, in particular for N-acetyl n-propyl derivatives of amino acids, δ values were within 0.25‰ of results obtained using conventional techniques and standard deviations were better than 0.35‰. Pooled data for measurements of all amino acids produced an accuracy and precision of 0.04 and 0.23‰, respectively, when 2 mnol of each amino acid was injected on column and 20% of the stream of combustion products was delivered to the mass spectrometer.     

Alpha-particle energy distributions from thin sources measured with small solid angles

The energy distribution of the alpha particles emitted from a source is in general complex. Only under particular circumstances, as in the case of very thin sources measured at large distances from the detector, can the energy distribution be approximated theoretically. In this work, we used the well-known code SRIM to simulate the interaction of alpha particles within a thin radioactive source and within the entrance window of a typical Si semiconductor detector. We considered several thin alpha particle sources measured at a large source-to-detector distance (small solid angle), in order to compare the distributions obtained by simulation with those determined by the theoretical model applied to this case. The study was performed for a variety of realistic alpha particle sources: UF₄, UO₂, U₃O₈, Gd₂O₃, and BaSO₄, considering as alpha emitters ²³⁵U, ²³³U, ¹⁴⁸Gd and ²²⁶Ra. For all these cases, we obtained the distributions due to the source and due to the entrance window of the detector, and also the final distribution given by the convolution of these two distributions. All the energy distributions obtained by simulation showed, in general, good agreement with the predictions given by the theoretical model, which includes corrections for Bohr straggling.     

A semi-empirical method for calculation of true coincidence corrections for the case of a close-in detection in γ-ray spectrometry

In this paper, a semi-empirical method is proposed to determine true coincidence-summing (TCS) correction factors for high resolution γ-ray spectrometry. It needs the knowledge of both full energy peak (FEP) efficiency and total-to-peak (TTP) efficiency curves. The TTP efficiency curve is established from the measurements with a set of coincidence-free point sources. Whereas for a volume source, the coincidence-free FEP efficiency curve is obtained iteratively by using the peaks from almost the coincidence-free nuclides and those from the coincident nuclides in the mixed standard sources. Then the fitting parameters obtained for both TTP and FEP efficiency curves are combined in a freely-available TCS calculation program called TrueCoinc, which yields the TCS correction factors required for any nuclide. As an application, the TCS correction factors were determined for the particular peaks of ²³⁸U, ²²⁶Ra and ²³²Th in the reference materials, measured in the case of a close-in detection geometry using a well-type Ge detector. The present TCS correction method can be applied without difficulty to all Ge detectors for any coincident nuclide.     

Performance of an air sampler and a gamma-ray detector in a small unmanned aerial vehicle

The performance of an air sampler and a small gamma-ray spectrometer was tested in an unmanned aerial vehicle (UAV) able to carry payload with mass up to 0.5 kg. Operation of the sampler was investigated with the aid of radon progeny normally present in outdoor air. Detection limits for several transuranium nuclides in air are of the order of 0.3 Bq m^?3 assuming 0.5 h sampling time and 1 h counting time in direct alpha spectrometry. Unshielded ¹³⁷Cs and ⁶⁰Co point sources at the ground level were used to test the CsI spectrometer. Detection limits are approximately 1 GBq or larger depending on the flying altitude.     

Analytical possibilities of different X-ray fluorescence systems for determination of trace elements in aqueous samples pre-concentrated with carbon nanotubes

This study was aimed to achieve improved instrumental sensitivity and detection limits for multielement determination of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Se, Pb and Cd in liquid samples by using different X-ray fluorescence (XRF) configurations (a benchtop energy-dispersive X-ray fluorescence spectrometer, a benchtop polarised energy-dispersive X-ray fluorescence spectrometer and a wavelength-dispersive X-ray fluorescence spectrometer).The preconcentration of metals from liquid solutions consisted on a solid-phase extraction using carbon nanotubes (CNTs) as solid sorbents. After the extraction step, the aqueous sample was filtered and CNTs with the absorbed elements were collected onto a filter paper which was directly analyzed by XRF.The calculated detection limits in all cases were in the low ng mL^− 1 range. Nevertheless, results obtained indicate the benefits, in terms of sensitivity, of using polarized X-ray sources using different secondary targets in comparison to conventional XRF systems, above all if Cd determination is required.The developed methodologies, using the aforementioned equipments, have been applied for multielement determination in water samples from an industrial area of Poland.     

Laser ablation isotope ratio mass spectrometry for enhanced sensitivity and spatial resolution in stable isotope analysis

Stable isotope analysis permits the tracking of physical, chemical, and biological reactions and source materials at a wide variety of spatial scales. We present a laser ablation isotope ratio mass spectrometry (LA‐IRMS) method that enables δ¹³C measurement of solid samples at 50 µm spatial resolution. The method does not require sample pre‐treatment to physically separate spatial zones. We use laser ablation of solid samples followed by quantitative combustion of the ablated particulates to convert sample carbon into CO₂. Cryofocusing of the resulting CO₂ coupled with modulation in the carrier flow rate permits coherent peak introduction into an isotope ratio mass spectrometer, with only 65 ng carbon required per measurement. We conclusively demonstrate that the measured CO₂ is produced by combustion of laser‐ablated aerosols from the sample surface. We measured δ¹³C for a series of solid compounds using laser ablation and traditional solid sample analysis techniques. Both techniques produced consistent isotopic results but the laser ablation method required over two orders of magnitude less sample. We demonstrated that LA‐IRMS sensitivity coupled with its 50 µm spatial resolution could be used to measure δ¹³C values along a length of hair, making multiple sample measurements over distances corresponding to a single day's growth. This method will be highly valuable in cases where the δ¹³C analysis of small samples over prescribed spatial distances is required. Suitable applications include forensic analysis of hair samples, investigations of tightly woven microbial systems, and cases of surface analysis where there is a sharp delineation between different components of a sample. Copyright © 2011 John Wiley & Sons, Ltd.     

Rapid measurement of 241Pu activity at environmental levels using low-level liquid scintillation analysis

A straightforward and rapid method has been developed for the determination of ²⁴¹Pu activities. Pu is chemically separated from the sample, purified and electrodeposited to produce a source for alpha spectrometric determination of ²³⁸Pu and ^239,240Pu. Pu is stripped from the disc with concentrated nitric acid and extracted into tri-octylphosphine oxide (TOPO)/toluene. The organic extract is then mixed directly with commercial liquid scintillation cocktail without any further purification procedures and the sample counted on a Wallac 1220 Quantulus liquid scintillation counter (LSC). ²⁴¹Pu activity is estimated via the ²⁴²Pu yield monitor acquired by alpha spectrometry measurement. Experimental results for the performance testing of a low-level liquid scintillation spectrometer and the data for the evaluation of the method using standard reference materials are presented.     

A high resolution mass spectrometric measurement system for a vacuum fusion apparatus

A high resolution mass spectrometric read-out system for a vacuum fusion apparatus is described. Rapid analyses are possible and the rate at which various gases are evolved can be monitored. Gas mixture assays are accomplished by scanning the nominal mass 28 peak. Serial measurements of CO⁺, N₂⁺ and C₂H₄⁺ are made. Thus detection and measurement of evolved hydrocarbons are possible. The results for silver and tin from a conventional vacuum fusion apparatus and the mass spectrometer apparatus are compared.     

High and very high resolution spectroscopy of the vibrational-rotational states of non-rigid molecules with particular emphasis on ammonia

Using the vibration-inversion-rotation Hamiltonian for ammonia [V. ?pirko, J.M.R. Stone and D. Papou?ek, J. Mol. Spectrosc. 60 (1976) 159], a modified theory is worked out for the Δk = ± 3n interactions between the inversion-rotation energy levels in the ground and excited state of NH₃ which takes into account the large amplitude inversion motion.The high sensitivity submillimeter-wave spectrometer RAD has been used to measure the inversion and inversion-rotation transitions in the ν₂ state of ¹⁴NH₃ in the 18–37 cm^?1 region with microwave accuracy. The frequencies of the inversion-rotation transitions in the ground and ν₂ excited states have been measured with the 0.014 cm^?1 resolution in the 35–300 cm^?1 region with a Fourier transform spectrometer. The ν₂ band frequencies have been measured under Doppler limited resolution (<0.002 cm^?1) with a diode laser spectrometer and with 0.03 cm^?1 resolution using a grating spectrometer in the 10 μm region.By a least squares fit of these data and the data of the infrared-microwave two-photon and infrared heterodyne measurements of the ν₂ band, a set of the molecular constants for the ground and ν₂ state is obtained which reproduces the experimental data within the precision of the experiment.     

Isotopic analysis of plutonium using a combination of alpha and internal conversion electron spectroscopy

A combination alpha and conversion electron spectrometer was developed to quantify ²³⁹Pu/²⁴⁰Pu and ²³⁸Pu/²⁴¹Am isotopic ratios of plated sources. The spectrometer was constructed with a commercially available low noise passivated ion-implanted planar silicon (PIPS) detector that was cooled to 77 K with liquid nitrogen. The combination spectrometer was used to quantify alpha-particles, conversion electrons, gamma-rays and X-rays associated with the decay of various plutonium isotopes and ²⁴¹Am. Two amplifiers operated in parallel with different gains allowed for simultaneous acquisition of the lower energy region (21-60 keV) for internal conversion electrons, gamma-rays and X-rays, and the higher energy region (5050 keV-5550 keV) for alpha-particles. Energy resolutions of 2.2 keV FWHM (full-width at half maximum) for the 38.7 keV M conversion electrons and 11.2 keV for the 5499.2 keV alpha-particles from ²³⁸Pu were measured. The energy resolution combined with a spectral deconvolution method was sufficient to be able to quantify the radioactivity using the alpha-spectra as well as the electron spectra; however, quantification of the radioactivity using the internal conversion electron spectra was more problematic because of the presence of X-rays, gamma-rays, Compton scatter electrons and the number of electron peaks present. Deconvolution of the alpha-spectra yielded ²³⁹Pu and ²⁴⁰Pu activities (as % of total Pu activity), which differed from expected values by -3.0% to 5.4%. Deconvolution of an internal conversion electron spectrum of a high ²³⁹Pu and low ²⁴¹Am activity sample yielded ²³⁹Pu and ²⁴⁰Pu activities, which differed by -17.1 and -35.5% relative to the alpha-measurements, respectively. Determination of the Pu activity using the electron spectra was more problematic in samples where the ²⁴¹Am activity dominated. Determination of ²³⁸Pu and ²⁴¹Am activity by the electron spectroscopy data was also obtained and compared with the alpha-spectroscopy results. Theoretical investigation of the removal of ²⁴¹Am or use of a 400 eV electron spectrometer indicated that the internal conversion electron spectra could be used to determine the ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu/²⁴¹Am (when present) activity with and without spectral deconvolution, respectively.     

Pu-239/Pu-240 isotope ratios determined using high resolution emission spectroscopy in a laser-induced plasma

Laser-induced breakdown spectroscopy (LIBS) has been applied for the determination of plutonium isotope ratios through direct observation of atomic emission from laser-induced plasmas at high resolution. The Pu-239/Pu-240 isotope shift of −0.355 cm⁻¹ from the plutonium atomic line at 594.52202 nm (Blaise et al., The Atomic Spectrum of Plutonium, Argonne National Laboratory Report ANL-83-95, 1984) is clearly resolved in our plasma conditions. Atomic emission is dispersed through a 2-m spectrometer in double pass mode and collected on an electronically gated, intensified charge-coupled device (ICCD) camera. The integrated peak areas obtained from curve-fitting closely match the Pu-239/Pu-240 isotopic ratios obtained from standard methods of thermal ionization mass spectrometry and gamma spectrometry. The observed plutonium linewidths were 0.19 cm⁻¹ (0.0067 nm). These linewidths are within the experimental error of the ideal instrument-limited linewidth, which is calculated to be 0.15 cm⁻¹ (0.0052 nm) based upon the known modulation transfer function for the ICCD system. This linewidth should allow LIBS to be applicable for isotopic ratio measurements for all of the light actinides.     

Determination of Th and U in bone ash by ICP-ion source mass spectrometry

The feasibility of ICP-ion source mass spectrometry (ICP-MS) for the determination of²³²Th and²³⁸U in bone ash was studied. Bone ash samples were further decomposed with concentrated nitric acid under pressure in PTF crucibles. The resultant solution was diluted and subjected directly to the measurement with an ICP mass spectrometer. The effects of diluting and removing matrix elements on ICP-MS measurements of these nuclides were studied. The accuracy of the determinations was evaluated with the measurement of NBS Human Lung (SRM 4351) which was originally certified for alpha activities of²³²Th and²³⁸U.