Determination of 129I/127I isotope ratios in liquid solutions and environmental soil samples by ICP-MS with hexapole collision cell

The determination of I-129 in environmental samples at ultratrace levels is very difficult by ICP-MS due to a high noise caused by Xe impurities in argon plasma gas (interference of Xe-129(+)), possible (IH2+)-I-127 interference and an insufficient abundance ratio sensitivity of the ICP mass spectrometer for I-129/I-127 isotope ratio measurement. A sensitive, powerful and fast analytical technique for iodine isotope ratio measurements in aqueous solutions and contaminated soil samples directly without sample preparation using ICP-MS with a hexapole collision cell (ICP-CC-QMS) was developed. Oxygen is used as reaction and carrier gas for iodine thermal desorption via the gas phase from solid environmental material in the sample introduction device coupled on-line to ICP-CC-QMS. A mixture of oxygen and helium as reaction gases in the hexapole collision cell was applied for reducing disturbing background intensity of Xe-129(+). After optimization of measurement procedures the detection limit for I-129(+) in aqueous solution was 8x10(-13) g ml(-1), which is better by about two orders of magnitude in comparison to the detection limit for I-129(+) in sector field ICP-MS. The detection limit for direct I-129(+) determination in contaminated environmental (soil) samples via gas-phase desorption without any additional sample preparation was 3x10(-11) g g(-1) (30 ppt). Furthermore, the results of the determination of I-129/I-127 isotope ratios at the 10(-5)-10(-6) level in synthetic laboratory standards and environmental soil samples from contaminated areas are given

Improvement of the detection limit for determination of 129I in sediments by quadrupole inductively coupled plasma mass spectrometer with collision cell

The previously developed sample introduction device for the hot extraction of iodine from environmental samples (soils or sediments) and on-line introduction of analyte via the gas phase in quadrupole inductively coupled plasma mass spectrometry with hexapole collision cell (ICP-CC-QMS) was equipped with a cooling finger, which allowed intermediate iodine enrichment and improved the detection limits for I-129 down to 0.4 pg g(-1) without any additional sample preparation. A mixture of oxygen and helium as reaction gases in the hexapole collision cell was used for reducing the disturbing background intensity of Xe-129(+). Oxygen was also used as the carrier gas for iodine thermal desorption and transport into the ICP-CC-MS. The developed analytical method was applied for I-129 determination at the ultra-trace level and for isotope ratio measurements of I-129/I-127 down to 10(-7) in contaminated sediments and in SRM 4357 (Ocean Sediment Environment Radioactivity Standard). The measured I-129/I-127 ratio of 5.3x10(-7) corresponded to the expected value of 4.45x10(-7) reported for this sediment in the certificate

LA-ICP-MS studies of cross section of NiCrAlY-based coatings on high-temperature alloys

A microlocal analytical technique using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was developed to investigate elemental diffusion at the interface of NiCrAlY-based coatings on high-temperature alloys. The surface of the cross section of alloyed sample was scanned with a focused laser beam (diameter of laser crater, 25 mu m; wavelength, 213 nm; laser power density, 10(11) W cm(-2)), and the laser ablation system was coupled to a double-focusing sector field ICP-MS. The capabilities of LA-ICP-MS using "linescan'' and "single point'' mode at laser energies of 2 and 4 mJ were compared. Alloy certified reference material (CRM) BAM-328-1 (BAM-Bundesanstalt fur Materialprufung, Berlin, Germany) with a similar matrix composition to the samples investigated was employed to determine the relative sensitivity coefficients (RSCs) of chemical elements to quantify the analytical data. The RSCs of analytes measured by LA-ICP-MS in alloy CRM vary between 0.2 and 2. In addition, other calibration procedures involving calibration curves and solution-based calibration were considered. LA-ICP-MS was used to study the lateral element distribution on NiCrAlY-based alloy and coating after oxidation in air (300, 1000, 5000, 15 000 hours) at a temperature of 980 degrees C, whereby an increasing loss of aluminium due to diffusion from coating into the high-temperature base alloy was observed. Furthermore, the diffusion of several substrate alloying elements (e.g., Co, Ta, Mo, W) into the coating after annealing was found, which could be the reason for the alteration of mechanical properties (high-temperature stability) or oxidation performance or both

Determination of Sr-90 at ultratrace levels in urine by ICP-MS

Sr-90 appears as a radionuclide in the decay series of nuclear fission and can therefore be found in nuclear waste or released by nuclear accidents. Current methods for the detection of this radionuclide are time consuming and may be prone to a large variety of interferents. In this work, inductively coupled plasma mass spectrometry is explored for the determination of Sr-90 in the presence of stable zirconium in urine. Specific techniques are investigated to remove this as well as other contributions to the background at m/z = 90. A quadrupole ICP-MS equipped with a hexapole collision cell is first explored (final LOD = 2 ng L-1 for water samples), however, the desired limit of detection for Sr-90 in urine is quite low (0.02 pg L-1). The performance of a double-focusing sector field ICP mass spectrometer (ICP-SFMS) is further investigated, which allows measurement of Sr-90 at the ultratrace level. Other potential interferences were investigated and instrumental detection limits are calculated as 3 pg L-1 for water samples. Final parameters include the use of a cool plasma and medium mass resolution in ICP-SFMS. The method is applied to the analysis of Sr-90 extracted from urine using a crown ether extraction resin and concentrated (enrichment factor: 200); high levels of natural strontium in the separated fraction (of about 1 mug mL(-1)) equate to higher detection limits (80 pg L-1) due to Sr-88(+) at m/z = 90 and the relatively low abundance sensitivity of ICP-SFMS at medium mass resolution of 6 x 10(-7). This detection limit in the separated fraction corresponds to the detection limit of 0.4 pg L-1 in the original urine sample. The recovery of Sr-90, determined with the developed analytical method in spiked urine samples, was in the range of 82-86%