Research articles
Development of a new
sensor for total organic
carbon (TOC)
determination
Luigi Campanella
Tommaso Ferri
Maria Pia Sammartino
Paola Sangiorgio and
Giovanni Visco
The authors
Luigi Campanella, Tommaso Ferri,
Maria Pia Sammartino, Paola Sangiorgio and
Giovanni Visco are at the Dept of Chemistry,
“La Sapienza” University, p.le A. Moro, 5, Rome, 00185,
Italy
Keywords
Sensor, Pollution, Water
Abstract
A sensor to determine TOC is described. It is based on the
photoassisted degradation of organic compounds
concurring to TOC and on the determination of the
resultant CO
2
. The sensor was successfully tested on target
molecules, demonstrating that the linear correlation
constant between TOC values and produced CO
2
varies
according to the considered compound so that absolute
value determination is not possible in largely
heterogeneous solutions but can only be referred to
reference compounds on the TOC scale.
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Total organic carbon (TOC) is one of the
indexes considered for the assessment of the
quality of aqueous solutions and the possible
associated environmental risks. In unpolluted
waters TOC is mainly due to humic
substances and to vegetal and animal partially
degraded matter (generally resistant to
microbial degradation). Lignin, fulvic acids
and tannins are the most abundant
compounds; although not well chemically
defined, these compounds can be considered
as complex polyphenols with some
characteristics typical of carbohydrates. These
natural materials show a complexing capacity
towards heavy metals that can heavily affect
their solubility, the metal concentrations can
therefore rise up to toxic levels.
In polluted waters TOC is mostly due to
anthropogenic contributions, such as
fertilizers, pesticides, surfactants, solvents;
thence its value gives useful information about
the quality of the considered matrices. In
surface waters the TOC depends on the type
of the water under consideration, but it is also
affected by several parameters such as
temperature, salinity, pH, microbial activity,
surrounding vegetation. The TOC value is
highly variable: from less than 1 mg/l in
underground or sea waters, to 2 –10 mg/l in
lake or river waters, up to 100 mg/l in marshes
and fens (Canadian Water Quality
Guidelines, 1996). Although no rule
establishes the maximum admitted TOC
value, being more important the quality of the
organic matter rather than its quantity, the
sudden change of its value is commonly
recognised as an important datum especially
to control overexposed regions and to give
important advance warning.
Classical methods for TOC determination
are mainly based on organic matter oxidation
at high temperature by strong oxidising agents
and following detection (generally by IR
spectrometry and conductometry) of the CO
2
produced.
More recent methods combine the action
of UV light with the oxidation so that, being
favoured radicalic reactions, high
temperatures are no more required. All these
Sensor Review
Volume 22 · Number 1 · 2002 · pp. 57–61
q MCB UP Limited · ISSN 0260-2288
DOI 10.1108/02602280210416169
Work supported by MURST (Ministry of
University, Scientific and Technological Research)
in the frame of the funded programs of relevant
national interest (ex 40 per cent); project “Novel
procedures and devices for improving
electroanalysis in real matrices”.
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