Page 135 - Inorganic Mass Spectrometry - Fundamentals and Applications

~nductively ~oupled Plas~a Mass Spectrometry 125

can be determined by using ICP-MS. Plants, animal feeds, fertilizers, food, rocks,
ores, alloys, semiconductors, superconductors, high-purity acids, high-purity
bases, reagents, plastics, and polymers have also been analyzed by ICP-MS. For
each of these sample types one or more of the attributes of ICP-MS (rapid,
multielement analysis; part-per-trillion to part-per-billion detection limits; large
dynamic range; high selectivity and specificity; isotope measurement; and small
required sample size) make it the method of choice. More than 2000 articles
describing applications of ICP-MS have been published, A small sample of these
applications is described later.
For many of samples, sample preparation is the most time-consuming step,
the step in which error is most readily introduced, and the process that is most
difficult to assess. Procedures for sample dissolution, filtering, extraction, etc.,
must be considered and chosen specifically for ICP-MS [218,219]. Spectral
overlaps due to molecular ions can be directly dependent on sample preparation
procedures. Contamination from reagents, glassware (or plastic ware), vessels,
sampling, handling, and sample exposure to the surrounding environment must be
very carefully controlled and assessed in order to make quantitative measurements
The
at concentrations as low as those measurable by ICP-MS. use of closed vessel
microwave digestion has grown increasingly more popular for ICP-MS sample
preparation because it often allows use of nitric acid for digestion, avoiding the
spectral overlaps caused by sulfuric, hydrochloric, and perchloric acids, and
minimizes sample cont~nation [2 19-2261.
There are still a good deal of art and experience as well as science required
for development of successful ICP-MS methods. A huge database of specific
sample preparation and ICP-MS analysis procedures is available in the literature
and should be consulted before beginning the analysis of samples. Many of the
ins~ment manufacturers maintain databases of downloadable methods and tech-
nical reports on their web sites, Despite the low detection limits and high selec-
S, preconcentration or separation of sample components before
analysis may be required. Numerous articles describing new analysis approaches
using ICP-MS continue to be published.

The role of metals and other elements in the health humans, animals, and plants
of
continues to be of great interest both on a routine basis and in research. Two recent
reviews described the important impact of ICP-MS in biomedical research [227,
2283. ICP-MS provides the ability to measure multiple elements at ultratrace
levels rapidly and to measure isotope ratios at low enough concentrations so that
stable isotope tracers can be used for biomedical research f2291. Much remains
unhown about the role of metals and their speciation on biological activity, in
large part as a result of inadequate measurement techniques.