Page 152 - Inorganic Mass Spectrometry - Fundamentals and Applications

teins) in human serum [408]. Selenite and selenate were measured by gas
chromatography-(GC)-ICP-MS after derivatization [409] using isotope dilution
calibration. HPLC-ICP-MS was used to measure selenium species in gastroin-
testinal extracts of cooked cod [410]. Retention times for selenomethionine,
selenocystine, sodium selenite, and sodium selenate standards were determined.
One of the peaks observed from the gastrointestinal extracts did not match any of
the standard compounds but appeared to be consistent with an organic species.
of
This points out one the limitations of separation techniques coupled to ICP-MS.
be
is
The retention or migration time used to identify the species, but this may not
unequivocal (in contrast to the certainty of the identification of a particular
element in a sample using ICP-MS). Capillary electrophoresis-ICP-MS was used
limits
to measure selenium species in human milk and serum with detection in the
10- to 5O-pgL range [41 l].
Chromium is used in a number of industrial processes and, as noted, has
toxicity that is highly dependent on its speciation. The combination of ion chroma-
tography and ICP-MS detection has been used to measure Cr(II1) and Gr(V1) in
waste water [412]. Ion-pairing HPLC-ICP-MS was used to measure chromium
* species in seawater [413]. Speciation of chromium dyes was also reported by
HPLC-ICP-MS [4 141.
Transport of metals in the environment critically dependent on speciation.
is
Often metals are associated with colloidal materials, fulvic acid, or humic acid.
Extensive research is ongoing to study the uptake capacity of these materials as
well as minerals, the distribution of elements in natural water samples, and
species-dependent means of remediation. Speciation of yttrium and lanthanides in
natural water has been reported [4 151 using size exclusion chromatography and
ICP-MS. Multistage filtration has also been used with ICP-MS measurement of
the separated fractions [416]. Kinetic studies of metal uptake rate as a function of
EDTA, NTA, and fulvic acid concentrations in the water have been described
[417].
Speciation of tin and lead is important in identifying their source in the
environment and pathway into humans and food. Organotin compounds were
commonly used in paints for ocean ships but are toxic to humans. Dibutyltin
(DBT), tributyltin (TBT), diphenyltin (DPhT), and triphenyltin (TPhT) were
measured in harbor water [41 S] and fish [419]. Organolead compounds were
commonly used in gasoline and still are in some countries. Ion-pairing reverse-
phase liquid chromatography with ICP-MS detection was used to measure in-
organic Pb2+, triethyllead, triphenyllead, and tetraethyllead [420]. After derivatiz-
ation, GC-ICP-MS has also been used [421].

Inductively coupled plasma mass spectrometry is becoming more and more
popular because of the low detection limits, high selectivity, and rapid multiele-