Electrospray ionization with controlled in-source fragmentation and atomization (ERIAD) is promising method for mass-spectrometric elemental analysis. This paper concerns the main analytical features and necessary instrumentation for ERIAD. The method is shown to be effective for more than 70 elements of the periodic table: those that present as cations in a water solution. It shows a high absolute sensitivity with a low spread from Li to U, and a detection limit of tens of parts per trillion. The soft ionization used results in the absence of plasma chemical reaction products, typical for inductively coupled plasma mass spectrometry, and the spectra are nearly free from interferences. The method does not require a high resolution and can be used for samples with an artificial isotopic content. The method is essentially valid for radiochemistry and metallomics, as it has the possibility to combine measurements of chemical, elemental, and even isotopic content simultaneously.
Auger electron spectroscopy and thermoresistive methods are used to study the physical processes leading to gas cooling of heated molybdenum filaments in a wide temperature range of 350-1300 K and pressures of 760-10-3 Torr, corresponding to the operating range of a Pirani-type vacuum sensor. Nitrogen was used as the gas. It is shown that nitrogen atoms chemisorbed on the surface do not contribute to gas cooling, which occurs only due to physisorbed N2 molecules. In the intermediate vacuum region of 10-3-1 Torr, the heater is cooled due to the equilibrium between the flux of incident and thermally desorbed molecules, which is well described by the Hertz--Knudsen formula and first-order desorption with an activation energy of ~0.55 eV. On the contrary, at high pressures close to atmospheric, this cooling occurs due to the thermal desorption of gas molecules from an almost filled monolayer, which reduces its relative efficiency by many orders of magnitude. Keywords: vacuum, adsorption, Pirani sensor, molybdenum, thermal desorption, nitrogen.
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