Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions
| Autor: | Sebastian Klopotowski, David Müller, Valerie Derpmann, Hendrik Kersten, Thorsten Benter, Yessica Brachthäuser, Christine Polaczek, Markus Langner, Klaus J. Brockmann, Walter Wißdorf |
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| Rok vydání: | 2016 |
| Předmět: |
geography
geography.geographical_feature_category Atmospheric pressure Chemistry Turbulence Capillary action 010401 analytical chemistry Flow (psychology) Analytical chemistry Laminar flow 02 engineering and technology Static pressure Mechanics 021001 nanoscience & nanotechnology Inlet 01 natural sciences 0104 chemical sciences Volumetric flow rate Physics::Fluid Dynamics Structural Biology 0210 nano-technology Spectroscopy |
| Zdroj: | Journal of the American Society for Mass Spectrometry. 27(9) |
| ISSN: | 1879-1123 |
| Popis: | In this work, the characteristics of gas flow in inlet capillaries are examined. Such inlet capillaries are widely used as a first flow restriction stage in commercial atmospheric pressure ionization mass spectrometers. Contrary to the common assumption, we consider the gas flow in typical glass inlet capillaries with 0.5 to 0.6 mm inner diameters and lengths about 20 cm as transitional or turbulent. The measured volume flow of the choked turbulent gas stream in such capillaries is 0.8 L·min(-1) to 1.6 L·min(-1) under typical operation conditions, which is in good agreement to theoretically calculated values. Likewise, the change of the volume flow in dependence of the pressure difference along the capillary agrees well with a theoretical model for turbulent conditions as well as with exemplary measurements of the static pressure inside the capillary channel. However, the results for the volume flow of heated glass and metal inlet capillaries are neither in agreement with turbulent nor with laminar models. The velocity profile of the neutral gas in a quartz capillary with an inner diameter similar to commercial inlet capillaries was experimentally determined with spatially resolved ion transfer time measurements. The determined gas velocity profiles do not contradict the turbulent character of the flow. Finally, inducing disturbances of the gas flow by placing obstacles in the capillary channel is found to not change the flow characteristics significantly. In combination the findings suggest that laminar conditions inside inlet capillaries are not a valid primary explanation for the observed high ion transparency of inlet capillaries under common operation conditions. Graphical Abstract ᅟ. |
| Databáze: | OpenAIRE |
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