Dissolved organic carbon (DOC) is one of the most important
quality parameters in water analysis today. In this connection,
humic substances (HS) play an important role because the major
portion of DOC in natural aquatic systems originates from HS.
HS show polyfunctional structures, which enables these compounds
to interact either with inorganic (e.g., heavy metals) or
organic substances (e.g., pesticides).1 The formation of heavy
metal complexes with HS strongly influences the mobility and
bioavailability of these metals in the environment. It is, therefore,
of great importance that reliable analytical methods are available
for DOC determinations in bulk samples but also for quantification
in chromatographic fractions of compounds which interact with
HS.
organic substance, which is the most important precondition
for DOC determinations by ICP-IDMS. The detection
limits achieved are 0.3 mg L-1 for bulk analyses and
7 10-4 íg s-1 for transient signals of chromatographic
peaks. The results for different water samples, analyzed
by ICP-IDMS and a conventional DOC method, agree
well within the limits of error. By using a 13C spike
solution, which also contains enriched isotopes of heavy
metals, simultaneous determinations of DOC and heavy
metal concentrations in separated fractions of complexes
with humic substances are possible by coupling ICPIDMS
with HPLC and using size exclusion chromatography.