Effect of added molecular gases (H2
discharge on high resolution mass spectrometer ion signal intensities
Viktoria Weinste...
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Victoria weinstein

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Victoria weinstein

  1. 1. Effect of added molecular gases (H2 discharge on high resolution mass spectrometer ion signal intensities Viktoria Weinstein1, Edward B.M. Steers1, Glyn Churchill 1 London Metropolitan University, 166-220 Holloway Road, London, N7 8DB, UK, Phone/FAX: +44-(0)20-7133-2177/ +44-(0)20-71334375 E 2 EAGLabs, 6707 Brooklawn Parkway, Syracuse, NY 13211, US 1. Introduction The effects of molecular gases (H2, O2, N2) in argon glow discharges investigated by optical emission spectrometry (OES)1,2,3. In the current work, mass spectrometry (MS) with Cu, Fe and Ti matrices, in order to understand glow discharge can be significantly affected by the presence in the plasma constituents. In these experiments, small fractions (0-2%v/v) of these gases intensities for sputtered analyte, plasma gas and trace gases were recorded Element GD Mass Spectrometer Thermo Fisher scientific Fast Flow Glow Discharge Plasma Source 2. Instrumentation Fast flow tube allows routine analysis and the ion transportation time from the sample to the cone is ~150us IntegratedIntensity This extensive study of the effects of molecular gases in glow discharges with various matrices provides evidence which confirms results of previous modeling and experimental investigations and will be linked to data obtained from similar sources using time of flight mass spectrometry and optical emission spectroscopy. Acknowledgement The authors wish to acknowledge support from the EU Marie Curie Research Training Network Gladnet Contract MRTN References [1] V. D. Hodoroaba, E. B. M. Steers, V. Hoffmann and K. Wetzig, J. Anal. At. Spectrom., 2001, [2] Spectrom., 2008, [3] T. 4. Discussion  In general, the concentration of molecular gases observed in analytical practice may be of the order of 0.2 % v/v or less. However we have extended our observations to higher concentrations in order to see the fuller picture and hence to gain a better understanding of the processes.  The observed changes in ion signals (in many cases, several orders of magnitude) are much greater than those observed by OES. It should be noted that with OES, the changes occur with the discharge itself, whereas for MS there will almost certainly be changes in the transport of the ions to the mass spectrometer.  The Ar+ signal shows a dramatic fall for all added gases, the magnitude depending very significantly on the matrix used (with H2, greater with Fe and Ti than with Cu), and on the added gas – much greater with hydrogen than with nitrogen and oxygen. These large decreases contrast strongly with some OES results1, in which Ar II lines increase in intensity (i.e. the population of excited Ar+ ions increases).  In most cases, the matrix ionic signal initially increases with added molecular gas, and then falls as the sputter rate decreases. With hydrogen, there is a small decrease in the Ti+ signal but a significant rise for Cu+, in general agreement with earlier results1. 2, O2, N2) in an argon analytical glow discharge on high resolution mass spectrometer ion signal intensities , Glyn Churchill2, Karol Putyera2, Martin Kasik2 220 Holloway Road, London, N7 8DB, UK, 71334375 E-mail: v.weinstein@londonmet.ac.uk EAGLabs, 6707 Brooklawn Parkway, Syracuse, NY 13211, US 1. Introduction discharges used for chemical analysis of solid samples have already been work, complementary studies were made using advanced high resolution understand better the mechanisms occurring in the plasma. Analytical results in plasma gas of traces of such molecular gases, often arising from sample gases were introduced into the discharge gas and the changes in ion signal recorded for various samples. Drop in sputter rates for Cu 1.E-17 1.E-15 1.E-13 1.E-11 1.E-09 1.E-07 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 IntegratedIntensity O2 conc. (% v/v). Oxygen 40Ar++ 40Ar16O+ 16O16O+ 16O+ 40Ar+ 63Cu+ 63Cu16O+ 63Cu++ Nitrogen 1.E-17 1.E-15 1.E-13 1.E-11 1.E-09 1.E-07 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 IntegratedIntensity H2 conc. (% v/v). Hydrogen 40Ar++ 40ArH+ 40Ar+ 63CuH+ 63Cu+ 63Cu++ 3. Results a. effect of various gases - Cu matrix 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 0.2 0.4 0.6 0.8 1 1.2 1.4 sputterrate[um/min] X2 conc. (% v/v). Drop in sputter rates for Cu H2 N2 O2 1.E-17 1.E-15 1.E-13 1.E-11 1.E-09 1.E-07 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 IntegratedIntensity N2 conc. (% v/v). Nitrogen 63Cu16N+ 40Ar++ 40Ar+ 14N14N+ 14N+ 63Cu+ 1.E-17 1.E-15 1.E-13 1.E-11 1.E-09 1.E-07 0 0.2 0.4 0.6 0.8 1 IntegratedIntensity H2 conc. (% v/v). Effect of H2 - Fe matrix 40Ar++40ArH+ 40Ar+ 54Fe+ 54FeH+ 54Fe++ 1.E-17 1.E-15 1.E-13 1.E-11 1.E-09 1.E-07 0 0.2 0.4 0.6 0.8 1 1.2 IntegratedIntensity H2 conc. (% v/v) Effect of H2 - Ti matrix 48Ti+ 50TiH+ 40Ar++ 40ArH+ 40Ar+ b. Effect of Hydrogen - Various Matrices 5. Summary This extensive study of the effects of molecular gases in glow discharges with various matrices provides evidence which confirms results of previous modeling and experimental investigations and will be linked to data obtained from similar sources using time of flight mass spectrometry and optical emission spectroscopy. Acknowledgement The authors wish to acknowledge support from the EU Marie Curie Research Training Network Gladnet Contract MRTN-CT-2006-035459. References [1] V. D. Hodoroaba, E. B. M. Steers, V. Hoffmann and K. Wetzig, J. Anal. At. Spectrom., 2001, 16 43-49. [2] P. Šmíd, E.B.M. Steers, Z. Weiss, J.C. Pickering and V. Hoffmann, J. Anal. At. Spectrom., 2008, 23, 1223-1233. [3] S. Mushtaq, E.B.M. Steers, J.C. Pickering, P. Šmíd, V. Weinstein and T. Gusarova, J . Anal. At. Spectrom. 2010, DOI: 10.1039/C0JA00013B

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