At Magnetic Peripherals Inc. success has many directions for a ...
Manager Material Analysis Magnetic Peripherals Inc. a subsidiary of Control Data Corporation and an OEM leader in design, development and manufacturing of advanced disk drive and magnetic recording heads has an opportunity for a Manager of the Material Analysis Department. This senior level technical manager directs the activities of engineers and scientists in the materials analysis department which consists o f chemical, metallurgical and magnetic analysis section. The analysis equipment includes SEM, ESCA/AUGER, F T I R , ion and liquid chromatography. Candidates should have considerable applicable experience including several years of management and an advanced degree in material or chemical science. We offer a complete benefit package and the opportunity t o work in a t r u l y high technology research and development environment. Please forward your resume in confidence or request an applicat i o n by contacting Matt Casale N R M 1 0 E , Magnetic Peripherals Inc., 7801 Computer Ave. South, Bloomington, MN 55435.
MAGNETIC PERIPHERALS INC. a Control Data Company
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ANALYTICAL CHEMISTRY, VOL. 55, NO. 14, DECEMBER
1983
pending on the aperture diameter and the physical design of the source, allows sufficient collisions with reagent molecules or electrons to ionize completely all the trace organic molecules introduced into the source. Due to the high neutral molecular density at atmospheric pressure, ions attain thermal equilibrium in a relatively short period, typically after a few collisions with the carrier gas. Ion loss due to recombination and diffusive losses to the reaction chamber represent the predominant loss processes at atmospheric pressure. In contrast, CIMS represents a lower pressure regime. For thermal equilibrium to be reached at pressures approaching 1 torr, relatively long residence times are required, typically on the order of a few milliseconds. Typically, nonequilibrium conditions exist in analytical CI sources, resulting in ionization of only a portion of the sample introduced. Also, the lack of thermal equilibration in a CI source leads to product ions that are excited and may not be collisionally stabilized. These CI product ions are then more likely to fragment than similar API product ions would be. Instrumental Variations As with other techniques, APIMS has gone through various design changes and applications. Following the original 63 Ni ionization design (5), a corona discharge model was developed. APIMS sources have been interfaced with an LC and a GC. APIMS has also been used for real-time environmental monitoring. Recent advances include the development of an API source for a standard Finnigan 4000 quadrupole MS and a design to accept nonvolatile samples. These developments will be discussed in this section. Corona Discharge vs. 63 Ni Source. While the earliest work in APIMS was performed by Horning and co-workers (5,18) using a 63 Ni foil as an electron source, the corona discharge ion source followed shortly thereafter. Horning et al. developed the corona discharge API source specifically for the LC/APIMS system (19-21). The advantage of the corona discharge source is primarily that a much larger analytical dynamic range is achieved and that both equilibrated and nonequilibrated conditions may be used. The reactant ion concentration is about 100 times that of the 63 Ni source (2i).The disadvantages of the corona discharge ion source include continual erosion of the discharge tip and orifice clogging due to sputtered material (6). The 6 3 Ni source has the advantage of being a simple, reliable source of electrons that undergo ther-
