Changes in plasma composition during the expansion into the first vacuum stage of an inductively coupled plasma mass spectrometer (original) (raw)
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Spectrochimica Acta Part B: Atomic Spectroscopy, 2009
Velocities of argon atoms and calcium ions were measured in the first vacuum stage of an inductively coupled plasma mass spectrometer using high-resolution laser-excited fluorescence spectroscopy. The calcium ions reached terminal velocities in the supersonic expansion that were consistently 5-6% higher than those of argon atoms, despite minimal differences in the masses of the two species. A computational model of the expansion was developed that shows the development of an ambipolar electric field along the expansion axis. With reasonable assumptions about electron temperatures in the expansion, the model accounts for the differences between the terminal velocities of the neutral argon atoms and the singly-charged calcium ions.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2006
The supersonic expansion in the first vacuum stage of an inductively coupled plasma mass spectrometer has been characterized by laserinduced fluorescence of metastable argon atoms in the expansion. Atom velocities and temperatures were determined from Doppler shifts and linewidths, respectively, in the excitation spectra of the argon atoms. Shock structures characteristic of a supersonic expansion, the barrel shock and the Mach disk, were manifest as bimodal velocity distributions. The terminal velocities reached by the atoms were characteristic of conditions in the plasma source upstream from the entrance to the vacuum interface. D
Spectrochimica Acta Part B: Atomic Spectroscopy, 2007
The effects of a mass-spectrometer sampling interface on the fundamental parameters of an argon inductively coupled plasma were studied. Laser-scattering techniques were used to obtain radially resolved values for electron number density (n e ), electron temperature (T e ), and gas-kinetic temperature (T g ) of the ICP upstream from the sampler as a function of applied r.f. power while different sample solutions were introduced. In addition, radially resolved calcium ion and atom number densities were determined under the same conditions in order to study the effects of matrix elements upstream from the mass spectrometer interface. It was found that the interface causes changes in the fundamental parameters that are dependent on the ICP applied r.f. power and the pressure at the back of the sampling interface. Furthermore, the changes caused by matrix interferents are different in the presence and in the absence of the sampler.
Spectrochimica Acta Part B: Atomic Spectroscopy, 1998
A portion of the ion beam in the second stage of an inductively coupled plasma mass spectrometer was mapped using laser induced fluorescence (LIF). With LIF relative density measurements are made in real time with minimal interference to the ion beam. We report axial measurements of Ba and Sc ion density from 22 to 45 mm behind the tip of the skimmer cone. Additionally, maps of radial ion density with and without Pb and Mg matrices are given for the same two analyte species. The results reveal that earlier ion deposition experiments dramatically underestimated the extent of the radial spread of the ion beam and the influence of matrix on the ion beam.
Mass spectrometry of ions from atmospheric pressure plasmas
2016
Nicht-thermische Atmospharendruckplasmen (Mikroplasmen) zeichnen sich durch hochenergetische Elektronen und niederenergetische Schwerteilchen (Neutrale und Ionen) aus. Diese Bedingungen fuhren zu komplexen plasmachemischen Prozessen und infolgedessen zu der Bildung von reaktiven Spezies. Dies ermoglicht den Einsatz in vielfaltigen industriellen und medizinischen Anwendungen. Im Rahmen der Arbeit wurde ein Messsystem zur Massenspektrometrie von Ionen aus Mikroplasmen entwickelt, charakterisiert und fur die Analyse einiger Mikroplasmenquellen angewendet. Der Schwerpunkt lag dabei in der Verifizierung des atmospharischen Ursprungs der gemessenen Ionen, was durch detaillierte numerische Simulationen des Extraktionsprozesses gelang. Die Untersuchungsergebnisse von Helium-Mikroplasmen zeigen, dass Verunreinigungen mit niedriger Ionisationsenergie eine notwendige Elektronenquelle in derartigen Plasmen darstellen.
Journal of Analytical Atomic …, 2012
An inductively coupled plasma connected to a mass spectrometer interface (sampling cone) is computationally investigated. Typical plasma characteristics, such as gas flow velocity, plasma temperature and electron density, are calculated in two dimensions (cylindrical symmetry) and compared with and without a mass spectrometer sampling interface. The results obtained from our model compare favorably with experimental data reported in the literature. A dramatic increase in the plasma velocity is reported in the region close to the interface. Furthermore, a cooled metal interface lowers the plasma temperature and electron density on the axial channel very close to the sampling cone but the corresponding values in the off axial regions are increased. Therefore, the effect of the interface strongly depends on the measurement position. It is shown that even a small shift from the actual position of the sampler leads to a considerable change of the results.
Spectrochimica Acta Part B-atomic Spectroscopy, 2003
Radial profiles of Ca and Sr ion number densities in an ICP at 6, 7 and 8 mm above the load coil (ALC) and at 1.25 kW of input rf power were measured by saturated fluorescence induced by an Nd:YAG laser-pumped dye laser at 396.85 nm and 421.55 nm, respectively. The measurements were performed in the presence and in the absence of an ICP-MS sampling interface. When in place, the orifice of the sampling cone was positioned 13 mm ALC on the axis of the plasma torch. The results show that the interface can either raise or lower the ion number densities, depending on the central-gas-flow rate, and can cause a vertical shift of their entire radial profiles with respect to the ICP axis. The introduction of Li, Cu and Zn as matrix elements reduced the ion number densities of the analytes, both in the presence and in the absence of the interface. This effect became more significant at higher central-gasflow rates. In addition, the peak value of the radial ion number density was found to depend strongly on the centralgas-flow rate maximum occurred at 1.1 lymin for both Ca ion and Sr ion under the ICP operating conditions used in this study. This behavior is very similar to the mass spectrometric signals previously observed downstream and reported in the literature. ᮊ
Evolution and revolution in instrumentation for plasma-source mass spectrometry
Pure and Applied Chemistry, 2000
Plasma-source mass spectrometry, usually in the form of inductively coupled plasma mass spectrometry (ICP-MS), has matured into a widely accepted method for ultra-trace multielemental analysis. However, the method exhibits shortcomings. For example, it does not provide adequate precision for isotope ratio measurements if many isotopes are to be determined. Moreover, isobaric overlaps (spectral interferences) can be very troublesome in some situations. Similarly, matrix interferences can adversely affect many determinations. Yet, it is in the area of high-speed transient measurements that ICP-MS perhaps suffers its greatest weakness. When sampling devices such as flow injection, laser ablation, electrothermal vaporization, or chromatography are employed, the user must choose between broad elemental or isotopic coverage and signal-to-noise ratio (S/N). In turn, compromised S/N means lower precision or poorer detection limits. Here, new instrumentation aimed at overcoming these limitations will be described. One system, based on a time-of-flight mass spectrometer, provides excellent detection limits, resolving power better than commercial quadrupole mass filters, precision of at least 0.02% rsd in a ratioing mode, and extraordinarily high speed for use with transient sampling devices. The second instrument is based on a sector-field mass spectrometer but, unlike other such units, is equipped with a focal-plane array detector. So equipped, the system can detect a broad mass range at once.
Miniature Thomson-type spectrometer for mass-and energy-analysis of pulsed plasma-ion streams
Czechoslovak Journal of Physics, 2006
The paper describes the construction and tests of a new miniature mass-spectrometer of the Thomson type, which has been designed especially for plasma-ion measurements inside vacuum experimental chambers, i.e. near the electrode outlets. This ion spectrometer enables ion mass-and energy-analysis to be performed at conditions, which are unavailable for typical ion-spectrometers placed outside the vacuum chamber. In order to record the investigated ions the use is made of solid-state nuclear-track detectors of the CR-39 or PM-355 type. A quantitative analysis of recorded ion tracks is carried out by means of an optical microscope equipped with a CCD camera coupled with a PC unit. Preliminary measurements by means of the described ion-spectrometer have been performed within the RPI-IBIS facility operated at about 50 kJ, with the pulsed injection of a working gas. The paper presents results of the detailed measurements of energy distributions of different ion-species, i.e. protons, deuterons and nitrogen ions, within the energy range from about 50 keV to about 300 keV.
Mass spectrometric and laser spectroscopic characterization of a supersonic planar plasma expansion
International Journal of Mass Spectrometry, 2004
A mass spectrometric and laser spectroscopic experiment has been performed to characterize reactive species that are formed in a supersonic planar plasma expansion generated by discharging a high-pressure gas pulse in a multi-layer slit nozzle geometry. Discharges through mixtures of nitrogen, water and acetylene in He have been studied. The mass spectrometric study uses a state-of-the-art time-of-flight setup. Besides (cluster) cations, with sizes as large as (H 2 O) 56 H + , a variety of pure carbon chain anions has been observed. The spectroscopic study uses cavity ring down spectroscopy and shows that a planar plasma is also suited to obtain rotationally resolved spectra of vibrationally excited metastable electronic states. The latter is demonstrated by the example of rotationally resolved transitions of the (v , v ) = (3, 0) and (4, 1) bands in the B 3 g ← A 3 + u electronic transition of molecular nitrogen.