主题：A Beginner’s Guide to ICP-MS（之一）

Amazingly, 18 years after the commercialization
of inductively coupled
plasma mass spectrometry
(ICP-MS), less than 4000 systems
have been installed worldwide. If
you compare this number with another
rapid multielement technique, inductively
coupled plasma optical emission spectrometry
(ICP-OES), first commercialized
in 1974, the difference is quite significant.
In 1992, 18 years after ICP-OES was
introduced, more than 9000 units had
been sold, and if you compare it with the
same time period that ICP-MS has been
available, the difference is even more dramatic.
From 1983 to the present day,
more than 17,000 ICP-OES systems have
been installed — more than four times
the number of ICP-MS systems. If the
comparison is made with all atomic spectroscopy
instrumentation (ICP-MS, ICPOES,
graphite furnace atomic absorption
[GFAA] and flame atomic absorption
[FAA]), the annual turnover for ICP-MS
is less than 7% of the total atomic spectroscopy
market — 400 units compared
to approximately 6000 atomic spectroscopy
systems. It’s even more surprising
when you consider that ICP-MS offers
so much more than the other
techniques, including two of its most attractive
features — the rapid multielement
capabilities of ICP-OES, combined
with the superb detection limits of GFAA.
ICP-MS — ROUTINE OR RESEARCH?
Clearly, one of the reasons is price — an
ICP-MS system typically costs twice as
much as an ICP-OES system and three
times more than a GFAA system. But in a
competitive world, the “street price” of an
ICP-MS system is much closer to a top-ofthe-
line ICP-OES system fitted with sampling
accessories or a GFAA system that
has all the bells and whistles on it. So if
ICP-MS is not significantly more expensive
than ICP-OES and GFAA, why hasn’t
it been more widely accepted by the analytical
community? I firmly believe that
the major reason why ICP-MS has not
gained the popularity of the other trace
element techniques is that it is still considered
a complicated research technique,
requiring a very skilled person to
operate it. Manufacturers of ICP-MS
equipment are constantly striving to
make the systems easier to operate, the
software easier to use, and the hardware
easier to maintain, but even after 18 years
it is still not perceived as a mature, routine
tool like flame AA or ICP-OES. This
might be partially true because of the relative
complexity of the instrumentation;
however, in my opinion, the dominant
reason for this misconception is that
there has not been good literature available
explaining the basic principles and
benefits of ICP-MS in a way that is compelling
and easy to understand for someone
with very little knowledge of the
technique. Some excellent textbooks (1,
2) and numerous journal papers (3–5)
are available that describe the fundamentals,
but they tend to be far too heavy for
a novice reader. There is no question in
my mind that the technique needs to be
presented in a more user-friendly way to
make routine analytical laboratories more
comfortable with it. Unfortunately, the
publishers of the “for Dummies” series of
books have not yet found a mass (excuse
the pun) market for writing one on ICPMS.
So until that time, we will be presenting
a number of short tutorials on the
technique, as a follow-up to the poster
that was included in the February 2001
issue of Spectroscopy.
During the next few months, we will be
discussing the following topics in greater
depth:
• principles of ion formation
• sample introduction
• plasma torch/radio frequency generator
• interface region
• ion focusing
• mass separation
• ion detection
• sampling accessories
• applications.
We hope that by the end of this series,
we will have demystified ICP-MS, made it
Figure 1. Generation of positively charged ions in the plasma.