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electric fields to be formed. As each drop continues to shrink, the electric fields become sufficiently
strong to cause the droplets to explode, producing ions. Due to the strength of the electric field, and the
large number of ions that are produced, many of the ions that are formed contain multiple charges. As
the mass spectrometer measures the m/z values of the ions, this, in effect, increases the mass range of
the spectrometer. The device has been the subject of much research and development, including the
introduction of novel nebulizing devices, special operating conditions, and modified ion producing
techniques. The atmospheric ionization interface operates in a similar way to the electrospray, except it
functions at atmospheric pressure, and the evaporated droplets are ionized by a corona discharge,
produced by a separate electrode system. Both the electrospray interface and the atmospheric ionization
interface have been used extensively in a wide range of analytical applications. The inductively coupled
plasma interface and the microwave coupled interface, have also been extensively employed in
elemental analysis, particularly in the determination and identification of trace metals. The permeable
membrane interface, similar to that described in the chapter on GC/MS, appears to have a limited field
of application in LC. The particle beam interface, another direct inlet interface, involves the ionization
of dry particles by electron impact, and has been found to function effectively, and appears useful in
some specific application areas.

References

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2. M. Karas and F. Hillenkamp, Anal. Chem., 60(20)(1988)2299.

3. M. A. Baldwin, and F. W. McLafferty, Biomed. Mass Spectrom., 1(1974)80.
4. R. P. W. Scott, C. G. Scott, M. Munroe and J. Hess. Jr., The Poisoned Patient: The Role of the
Laboratory, Elsevier, New York (1974)395.

5. A. T. James, J. R. Ravenhill and R. P. W. Scott, Chem. Ind., (1964)746.

6. R. P. W. Scott and J. F. Lawrence, J. Chromatogr. Sci., 8(1970)65.

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8 N.J. Alcock, C. Eckers, D. E. James,M. P. L. Games, M. S. Lant, M. A. McDowall, M. Rossiter, R.
W. Smith, S. A. Westwood and H.-Y. Wong, J. Chromatogr., 251(1982)165.

9. D. E. Games, M. J. Hewlins, S. A. Westwood and D. J. Morgan, J. Chromatogr., 250(1982)62.