Spark source mass operation

Qualitatively, the spark source mass spectrum is relatively simple and easy to interpret. Most instrumentation has been designed to operate with a mass resolution Al/dM of about 1500. For example, at mass M= 60 a difference of 0.04 amu can be resolved. This is sufficient for the separation of most hydrocarbons from metals of the same nominal mass and for precise mass determinations to identify most species. Each exposure, as described earlier and shown in Figure 2, covers the mass range from Be to U, with the elemental isotopic patterns clearly resolved for positive identification. 

While our research was concerned with developing wet chemical methods, we confirmed our data with analyses from an available spark source mass spectrometer (SSMS). The SSMS operating parameters are given in Table I. The instrument used was an AEI MS-7 (I, 2) equipped with electrical detection. It was used in the peak switching mode only to provide more precise analyses. 

Isotope Dilution By Spark Source Mass Spectrometry. A unique and quite different approach to determining trace elements in solids, liquids, and gases uses the isotope dilution technique. This method has been operational for some time with mass spectrometers. Thermal ionization... 

Spark Source Mass Spectrometry. Another method for trace analysis probably should be mentioned and that is spark source mass spectrometry. In this technique, the sample in the form of a solid serves as an electrode and vapors, formed by sparking, are atomized and ionized to metal ions which are separated by a mass spectrometer and measured. The equipment is expensive and good results require the attention of a skilled operator. Even under the best conditions order of magnitude agreement of results is about the best that can be achieved. 

In the sources used in optical atomic spectrometry, con.siderable ionization takes place, so they are useful ion sources for mass spectrometry [50]. Although, an overall treatment of instrumentation for mass spectrometry is given elsewhere (- Mass Spectrometry), the most widely used types of mass spectrometer are briefly outlined here. In particular, the new types of elemental mass spectrometry have to be considered, i.e.. glow discharges, and inductively coupled and microwave plasmas. In contrast to classical high voltage spark mass spectrometry [51] or thermionic mass spectrometry [52], which are beyond the scope of this article, the plasma sources are operated at considerably higher pressure between some 10 Pa and atmospheric pressure than the pressure in the mass spectrometer itself (10 Pa). Con-... 

The glow-discharge source appears to be more stable than the spark source and is less expensive to purchase and operate. It is particularly useful for the direct analysis of solid samples. Commercial quadrupole and double-focusing mass spectrometers with glow-discharge sources are now on the market. 

Mass spectrometry is a sophisticated instrumental technique that produces, separates, and detects ions in the gas phase. The basic components of a mass spectrometer are shown in Figure 20.9. A sample with a moderately high vapor pressure is introduced in an inlet system, operated under vacuum (10"" to 10 ton) and at high temperarnre (up to 300°C). It vaporizes and is carried to the ionization source. Nonvolatile compounds may be vaporized by means of a spark or other... 

The basic layout of the instrument is shown in fig. 37B.1. The source parts which are exposed to the spark are made of tantalum, which has one major isotope at mass 181. The electrode holders may be moved from the outside, through bellows, during operation. The source area can be isolated from the main vacuum by hydraulic valves to allow the sample to be changed. 

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