Page 5 - 5_TOC in daily practice
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Sum parameter – Total Organic Carbon
Determination of the purgeable organic
carbon (POC)
SCA-130-502
According to EN 1484, which contains the Here, the volatile organic compounds are
instructions for TOC determination, the POC converted to CO 2 and detected via NDIR
(purgeable organic carbon) is the TOC detector.
content that can be expelled under the
conditions of this method. This information is
very unspecific and should be described here TOC
in more detail.
The instruments in the TOC-L series can be NPOC POC
extended with an option to include
measurement of the POC parameter. The
core feature of this option is the LiOH trap,
which is placed in the flow line of the Fig. The addition method (NPOC + POC)
analyzer. During the course of the addition method, the
remainder is used for NPOC determination.
However, in the drinking water application or
ultrapure water application, the POC content
is completely negligible. Here, TOC = NPOC
The POC can, nevertheless, play an
important role in wastewaters, particularly in
industrial effluents.
■ Calibration
Particular attention should be paid to
calibration of the POC. Standards that are
prepared with volatile, purgeable organic
substances are inherently very unstable. This
For POC determination, the sample is is why IC standard solutions (prepared from
aspirated using the TOC-L injection syringe, carbonates and/or hydrogen carbonates) are
acidified with HCL and subsequently purged used for POC calibration. Sampling of the IC
using carrier gas. In this step, CO 2 originating solutions for POC determination is carried out
from carbonates and hydrogen carbonates as using the TOC-L injection syringe. The IC
well as all volatile organic compounds (POC) solution is acidified in the syringe. The
are purged from the solution. The LiOH trap inorganic substances of the standard solution
binds the CO 2 from the gas mixture are converted to CO 2 and transferred to the
(originating from the TIC). The volatile NDIR detector using a carrier gas.
compounds pass the trap and reach the
catalyst.
