Page 11 - 1_Environmental analysis

Sum parameter – Total Organic Carbon
TOC determination in solid samples
using the suspension method
SCA-130-105
The TOC content in solids plays an important
role in the classification of soils, sludges and
sediments. According to the German
Ordinance on Environmentally Compatible
Storage of Waste from Human Settlements
(Abfallablagerungsverordnung, AbfAblV),
TOC in solid materials is one of the key
parameters for the characterization of wastes
as part of the acceptance control of landfills.
This important control measure requires a
fast and simple TOC determination method
and, at the same time, a robust and
statistically reliable method that is based on
the inhomogeneous composition of soils.
To date, the established regulations describe
a method whereby a weighed solid sample is
combusted in a stream of air or oxygen. The
generated during combustion is
CO 2
subsequently detected and quantified using a
calibration curve. The inhomogeneity of the
soils has a direct effect on the distribution of
the measuring data – each weighed solid
sample can only be combusted once.
■ Suspension method
Several years ago, Shimadzu developed the
so-called suspension method in cooperation
with responsible authorities and the Albo-tec
environmental laboratory in Bochum,
Germany. In this method, the solid sample is
processed in a specific way so that it can
subsequently be treated as a liquid, particle-
containing sample. This method was
successfully applied in several round robin
tests and has, since June 2009, also been
described in the draft DIN EN 159536. This
new standard is intended to replace DIN EN
13137 and describes the established solid
sample combustion method as well as the
novel suspension method (see annex).
■ Analytical process
Approximately 200 mg of the dried and
ground sample is weighed into an Erlenmeyer
flask. The sample is subsequently suspended
in a diluted hydrochloric acid solution. The
acidic solution serves to break down the
carbonates present in the sample and, at the
same time, form the suspension medium.