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3.3.3 TIC analysis
During the TIC analysis the total inorganic carbon from carbonates and
hydrocarbonates as well as free CO
2
is detected.
Cyanides, cyanate, isocyanate and carbon particles are not detected.
An aliquot of the sample is directly dosed into the TIC reactor to determine the
inorganic carbon materials (TIC). The CO
2
is purged and detected.
3.3.4 NPOC analysis
During the NPOC analysis the total non-purgeable organic carbon content of a sample
is detected.
The sample is acidified to pH 2 outside of the analyzer with H
2
SO
4
(c = 2 mol/l) and
the resulting CO
2
is purged. Afterwards the remaining carbon from the sample
prepared in this manner is digested via the UV reactor and detected in the detector.
Other highly volatile organic compounds are purged with the CO
2
. The NPOC analysis
should not be used when the sample contains easy to purge organic substances.
3.3.5 NPOC analysis according to the NPOC plus method
This method is particularly suited for the detection of low TOC contents in samples
with high TIC contents or a high level of dissolved CO
2
. Generally the NPOC method is
recommended for the analysis of such samples. With high and, in particular, unknown
TIC contents very long time periods (t > 10 min) may, however, be required for the
complete purging of the CO
2
.
As far as the process is concerned, the NPOC plus method is a combination of the
NPOC and differential method.
As with the NPOC analysis the sample is acidified to pH 2 with H
2
SO
4
(c = 2 mol/l)
outside the analyzer. Immediately before the analysis of the sample the greater part of
the carbon dioxide generated is purged externally. Afterwards the remaining organic
carbon (TOC) from the sample prepared in this manner is determined using the
differential method.
The TIC value determined using this method is only a calculated variable and of no
analytical relevance.
Highly volatile organic substances are purged partly during the first step and are
therefore not entirely detected.