Laser ablation ICP-MS is incredibly versatile. In theory, any
solid material can be analyzed provided the laser can couple with
the material, external standards are available, and internal
standards are known. The advantages of LA-ICP-MS over conventional
solution nebulization ICP-MS have been reported by many authors
[e.g., Denoyer et al., 1991; Jarvis and Williams, 1993;
and Longerich et al., 1993]: (A) Analysis of solid samples is
direct and requires no lengthy dissolution processing which may be
incomplete and can also potentially introduce contamination to the
sample; (B) Analysis of solid samples by LA-ICP-MS requires little
preparation (a flat surface may be required if the entire sample is
to be probed, but it need not be parallel to better than 200 
m
provided that the focus of the laser does not change from one part
of the sample to another, resulting in different ablation
characteristics); (C) a dry sample is introduced to the plasma with
a resulting lack of polyatomic interference species produced by the
interaction of water and acid species with the argon plasma.
Compared to other microsampling analytical techniques, LA-ICP-MS
has several distinct advantages: 1) Laser probing utilizes light
rather than charged particles and can, therefore, analyze both
conducting and non-conducting material without the need for a
conductive coat and/or other charge balancing techniques, as in
SIMS and electron microprobe techniques; 2) no vacuum is required
in the sample chamber, although an airtight seal is; 3) LA-ICP-MS,
unlike Atomic Emission Spectroscopy, separates the ionization step
from the sampling step---the laser is used to ablate the sample
only and the material is transported to the secondary plasma source
in the torch of the ICP. Therefore, both steps can be
independently controlled and optimized; 4) the high sensitivity of
the ICP-MS allows small samples to be quantified, which is ideal
for LA-ICP-MS in that spatial resolution can be used to investigate
compositional gradients across a sample, even though the laser
sampling area is 5-10 times greater than that obtained for the
electron or ion microprobes [ Reed, 1989, 1990]. However, the
spatial resolution and detection limit of LA-ICP-MS is being
constantly reduced for in situ analysis of solid samples
[e.g., Jackson et al., 1992; Pearce et al., 1992a;
Neal, 1993; Feng, 1994]. For example, Gray [1985]
reported a pit diameter of 700 
m, whereas Jackson et al.
[1992] and Neal [1993] reported pit diameters of 20-30
m---a 96% decrease over 7-8 years. Finally, trace-element
analysis using LA-ICP-MS does not require involved interference
corrections inherent in SIMS analysis and the hardware is
considerably cheaper. Given this proviso, it has been found that
a larger number of elements can be accurately quantified by
LA-ICP-MS over SIMS, provided well characterized standards are
available, with a detection limit similar to that of SIMS
[ Denoyer et al., 1991].