Corrected equation for the concentrations in the drift tube of a proton transfer reaction-mass spectrometer (PTR-MS).

A corrected equation for the concentrations in the drift tube of a proton transfer reaction-mass spectrometer (PTR-MS) is presented which accounts for the different mobility of primary ions and protonated analyte previous termvolatilenext term organic compounds (VOCs). As a consequence, the calculation of VOC concentrations from the measured count rates requires as well a correction factor, equalling the ratio of (i) the mobility of the protonated analyte VOCs to (ii) the mobility of the gases used to determine the transmission efficiency. However, such data do essentially not exist for the relevant VOCs. Published mobility data for small inorganic ions suggest that the correction can be larger than 20% and hence be a significant contribution to the overall accuracy of calculated concentrations. The correction emphasises the need to calibrate the PTR-MS in order to determine VOC concentrations accurately

Comparisons of 239Pu inhalation doses calculated with ICRP 67 and proposed systemic models.

The International Commission on Radiological Protection (ICRP) has issued an age-specific systemic biokinetic model for plutonium (Pu), which was later modified to give better agreement with measured urinary excretion data. Recently, the current ICRP systemic Pu model was improved by Leggett et al. based on recently developed data. Incorporation of 239Pu in the human body may result in significant internal radiation exposure. In the present work, the retentions in organs and tissues, the equivalent dose and effective dose from 239Pu for workers and members of the public were estimated and compared under the current ICRP and the proposed models. 239Pu contents in liver and in other soft tissue calculated with the proposed model are higher than predicted by the ICRP model, whereas bone content is lower than predicted by the ICRP model. Based on the proposed model, the inhalation equivalent dose coefficient in some organs, e.g. liver and kidneys, is increased, but there is no significant change in the effective inhalation dose coefficients of 239Pu for workers and members of the public

Multidimensional statistical analysis of PTR-MS breath samples: A test study on irradiation detection.

A multidimensional statistical analysis of data obtained from breath gas measurements with Proton Transfer Reaction-Mass Spectrometry (PTR-MS) is proposed, based on a chemical-diffusion equilibrium approach. The proposed methodology is developed and demonstrated on the problem of detecting exposure of human beings to ionizing radiation. It could be applied to a general family of non-invasive, high-throughput, breath gas based detection strategies, like for instance a breath gas test for early diagnosis of lung cancer

Method development for thermal ionization mass spectrometry in the frame of a biokinetic tracer study with enriched stable isotopes of zirconium.

Isotope dilution in thermal ionization mass spectrometry (ID-TIMS) is a precise method for quantification of isotope ratios in geological samples, or for trace elements analysis in geological and environmental samples. This work presents an optimized ID-TIMS method for application in the field of life sciences, more precisely in the frame of a human biokinetic study on zirconium with oral and intravenous administration of two stable isotope tracers. The method allows analyzing simultaneously different stable zirconium isotopes (two isotopically enriched artificial tracers and the natural background) in human blood plasma and urine. By optimization, tracer detection limits below 1 ng ml(-1) could be achieved. The biological samples were prepared by microwave-assisted acidic pressure digestion followed by extraction chromatography. The purified zirconium from the samples was measured on carbon-coated rhenium single filaments. Multiple channel electron multipliers were used as detectors. Interferences were observed from molybdenum isotopes and were corrected for based on the (95)Mo count rate. Isotope ratios of zirconium were determined in ranges of 0.016-2.84 ((91)Zr/(90)Zr), 0.020-2.46 ((92)Zr/(90)Zr), 0.115-10.93 ((94)Zr/(90)Zr), and 0.004-5.70 ((96)Zr/(90)Zr). The respective relative uncertainties lay in the range of 0.03-4.2%. Typical relative uncertainties of tracer concentrations were 4%

Effects of carbon dioxide in breath gas on proton transfer reaction-mass spectrometry (PTR-MS) measurements.

PTR-MS is becoming a common method for the analysis of volatile organic compounds (VOCs) in human breath. Breath gas contains substantial and, particularly for bag samples, highly variable concentrations of water vapour (up to not, vert, similar6.3%) and carbon dioxide (up to not, vert, similar6.5%). The goal of this study was to investigate the effects of carbon dioxide on PTR-MS measurements; such effects can be expected in view of the already well known effects of water vapour. Carbon dioxide caused an increase of the pressure in the PTR-MS drift tube (not, vert, similar1% increase for 5% CO2), and this effect was used to assess the CO2 concentration of breath gas samples along the way with the analysis of VOCs. Carbon dioxide enhanced the concentration ratio of protonated water clusters (H3O+H2O) to protonated water (H3O+) in the drift tube. Using the observed increase, being not, vert, similar60% for 5% CO2, it is estimated that the mobility of water cluster ions in pure CO2 is almost 65% lower than in air. Carbon dioxide had a significant effect on the mass spectra of the main breath gas components methanol, ethanol, 1-propanol, 2-propanol, acetone, and isoprene. Carbon dioxide caused a small increase (<10% for 5% CO2) of the normalised main signals for the non-fragmenting molecules methanol and acetone. The increase can be much higher for the fragmenting VOCs (ethanol, propanol, and isoprene) and was, for 5% CO2, up to not, vert, similar60% for ethanol. This effect of CO2 on fragment patterns is mainly a consequence of the increased abundance of protonated water clusters, which undergo softer reactions with VOCs than the hydronium ions. Breath gas samples stored in Teflon bags lost not, vert, similar80% of CO2 during 3 days, the decrease of VOC signals, however, is mainly attributed to decreasing VOC concentrations and to the loss of humidity from the bags

Hintergrundinformationen zu Polonium-210 und Betrachtungen zur Biokinetik und internen Dosimetrie vor dem Hintergrund des Falls Litwinenko.

Durch den mysteriösen Tod des früheren Geheimdienstoffiziers Alexander Litwinenko am 23. November 2006 wurde das bisher nahezu unbekannte Radionuklid 210Po plötzlich in den Fokus des öffentlichen Interesses gezogen. In diesem Zusammenhang sollen hier einige allgemeine Hintergrundinformationen über dieses Radionuklid aufgezeigt werden, ebenso wie detaillierte Informationen zur Biokinetik und Internen Dosimetrie. Die Ergebnisse werden vor dem Hintergrund des Falls Litwinenko zur Abschätzung der  esundheitsrisiken von möglicherweise kontaminierten Personen aus Deutschland näher diskutiert. Es zeigten sich jedoch keine Hinweise auf eine Kontamination mit 210Po bei den im  GSF-Forschungszentrum für Umwelt und Gesundheit untersuchten Personen