Vol. 23, No. 1
In Situ Monitoring of Aquatic Systems: Chemical Analysis and Speciation.
Vol. 6, IUPAC Series on Analytical and Physical Chemistry of Environmental
Systems (Series Editors: Jacques Buffle and Herman P. van Leeuwen).
Edited by Jacques Buffle and George Horvai. John Wiley & Sons Ltd.
(2000), pp. xviii + 1-623. ISBN 0-471- 48979-4.
To enable efficient interpretation of the functioning of ecosystems
such as lakes, oceans, or ground water, the recording of large data
sets is essential, in order to take into account natural spatial and
temporal variations correctly. This undertaking requires the use of
a network of in situ or onfield sensors or analytical devices, for continuous,
real-time monitoring of major, minor, and trace components, simultaneously
at a large number of locations in the ecosystem, and at various depths
in the water columns or ground water. Such a huge number of analyses
is not feasible by using the classical approach based on sample collection,
storage, and transportation, followed by sample handling in the laboratory.
Robust sensors and instruments for automatic in situ or on-site measurements
should thus be developed. This approach is required not only for the
reason of cost effectiveness, but also for scientific reasons.
Indeed, determinations of minor and trace inorganic and organic compounds
have become more and more important for water quality assessment. Classical
analyses of these compounds, however, are often prone to many artifacts
that can only be overcome by in situ measurements, avoiding the sampling
This book includes the most important in situ sensors and analytical
systems. Chapter 1 discusses general concepts that should be considered
for the development of any type of sensor, in order to get reliable
and environmentally relevant information. It also helps the reader to
place the various chapters in perspective to each other, inside a common
frame. The next four chapters deal with sensors for in situ measurements
of major components: O2 (Chapter 2), pH and CO2
(Chapter 3), S2- (Chapter 4), and Ca2+ and
N species (Chapter 5). Chapters 6, 7, and 9-11 deal with sensors
and analytical systems for minor or trace organic or inorganic components.
In these cases, the signal most often depends on the speciation of the
test analyte. All these chapters thus discuss speciation aspects relevant
to each technique. Chapter 8 is specifically devoted to the physicochemical
principles needed to understand how dynamic chemical equilibria, such
as metal complexation, affect the signal of analytical devices based
on flux measurements. Because most trace compound determinations are
based on such flux measurements, we have found it important that a rigorous
formulation of these general physicochemical concepts, and some examples
of their applications to a few sensor types, be described in a specific
Finally, the book ends with the existing microtechniques that could
be used for the fabrication of in situ sensors or microanalytical systems.
Although very few complete analytical systems have yet been built based
on this technology, and none of them for environmental application,
it is clear that the fabrication of at least key components (such as
microelectrodes, microreactors, etc.) of in situ analytical devices
should thus greatly profit from microtechnologies. The main purpose
of this chapter is to stimulate ideas for new microsensor or microanalytical
system construction, by using the concepts of microsensors described
in Chapters 2-6, which were built with more classical technologies.
This book should provide researchers interested in the development
of in situ sensors and analytical systems with the appropriate updated
literature and critically evaluated information. However, we hope that
it will be even more helpful to laboratories in charge of water quality
assessment, by providing them with updated information on existing sensors
and analytical systems, their present capabilities, and the expected
future developments. In most cases, either detailed technical information
is given or the corresponding literature is cited, which should help
any interested scientist to start using these analytical devices in
an appropriate manner. Thanks to the theoretical background discussed
in particular for methods related to speciation, correct interpretation
of the data should also be made easier, even for the nonspecialist.
University of Geneva,
Technical University of Budapest,