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Sapphire (α-Al2O3, transparent corundum) single crystals were analyzed with pulsed direct current glow discharge mass spectrometry. Combined hollow cathode was used as a discharge cell. To obtain stable sputtering of dielectric material, a formation of initial surface conductivity via preliminary vacuum deposition of thin metallic layer was proposed. Al and Ta film of different thickness (30–200 nm) were considered for this purpose. The approach was found to provide the effective sputtering of dielectrics. The formation of an oscillating system was shown during the sputtering of sapphire samples in a tantalum combined hollow cathode cell. For oriented sapphire single crystals, periodic oscillations of 27Al+ intensity were acquired. This phenomenon was observed only for dielectric single crystals and not for other dielectric samples, e.g. alumina ceramic or fused quartz. The linear dependence of oscillation period on the duration of discharge pulse was found. The origin of these oscillations seems to be attributed to periodic fluctuations of surface conductivity. Oscillation periods calculated for two different orientations of sapphire single crystals (001 and 012) were found to be proportional to the main period of sapphire lattice. Therefore, an assumption that the crystal internal structure of the sample might be the cause of the oscillations is discussed.

A method has been developed for the determination of 24 elements (As, B, Ce, Co, Dy, Fe, K, La, Lu, Mg, Mn, Na, Nb, Nd, P, Pr, Rb, S, Sb, Si, Sm, Th, Ti, and U) in ore samples by pulsed direct curr...

After the Chernobyl nuclear accident in 1986, numerous specimens of the so-called ‘fuel-containing masses’ or the Chernobyl ‘lava’ and hot particles were collected. Isotope analysis of Chernobyl specimens is the subject of special interest, since unexpected results on 238U/235U ratio has been reported previously. Although, over 30 years have passed since the Chernobyl accident, these samples are still a source of important information about the catastrophe as well as about the environmental behavior of highly radioactive materials. In the current study, glow discharge mass spectrometry with combined hollow cathode, pulse power supply and time-of-flight mass spectrometer was employed for the isotope analysis of uranium in Chernobyl-born microparticles. Six Chernobyl specimens (three crystals of artificial high-uranium zircon from the Chernobyl ‘lava’ and two hot particles) were analyzed. The method was optimized to cope the adverse oxide interferences. Simple isotope calibration with a single reference material of UO2 with known 235U content (abundance, 1.80 ± 0.03%) was used. The validity of the method was checked using the sample with natural 235U abundance (0.72%) and by comparing with sector field inductively coupled plasma mass spectrometry. The relative error of 235U determination was ca. 1%, which is comparable to or excels the values, obtained by the competitive approaches (e.g. laser ablation inductively coupled plasma mass spectrometry, accelerator mass spectrometry or resonance ionization mass spectrometry). An important advantage of the developed method is the possibility to conduct direct analysis with partial preservation of varied solid materials without preliminary dissolution, separation or concentrating procedures. Other than partial sample preservation, this provides lower hazards to the analyst, owing to shorter sample handling time and lower probability of radioisotopes volatilization or their turning to aerosols.

A direct method of uranium and thorium determination in non-conducting geological samples using time-of-flight mass spectrometry with pulsed glow discharge was proposed. The following rock specimens were analysed: metamict zircon, metamict rinkite, metamict samarskite (Y–Fe-niobate), pyrochlore and jacinth. For sample sputtering a combined hollow cathode cell of high purity aluminium or tantalum hollow cathodes was used. Powdered or monolith samples were pressed into the surface of the powdered metal prior to analysis. Model samples (artificial mixtures of oxides) were proposed for calibration; additionally, relative sensitivity factors, internal standardisation and standard additions were employed. For validation, IAEA artificially prepared uranium ore reference material was analysed. For additional validation, the obtained results for real mineral samples were compared to the results of inductively coupled plasma optical emission spectrometry after sample dissolution and semi-quantitative data of energy dispersive X-ray spectrometry. Limits of detection (3σ) for the designed method were 0.3 ppm for uranium and 0.5 ppm for thorium, which is comparable to laser ablation inductively coupled plasma mass spectrometry. The method was also tested for capability to measure isotope ratios for lead and uranium without specific isotope calibration. Acquired isotopic ratios of uranium and lead corresponded to their natural abundances within the experimental error.