multi N/C pharma HT
Function and design
27
The sample aliquot is dosed directly into the hot zone of the filled reactor (combustion
tube). Here, the pyrolysis and oxidation of the sample in the carrier gas flow is per-
formed with the aid of the catalyst. The carrier gas is also used as an oxidizing agent.
R + O
2
→ CO
2
+ H
2
O (1)
R-N+ O
2
→ NO + CO
2
+ H
2
O (2)
R-Cl+ O
2
→ HCl + CO
2
+ H
2
O (3)
R - carbonic substance
The measuring gas is cooled in the condensation coil and condensed water is separated
from the measuring gas in the subsequent TIC condensate container. After further dry-
ing and removal of corrosive gases, the CO
2
measuring gas is added to the NDIR detector
or NO detector.
Inorganic carbon is detected by injecting a sample aliquot into the acidic TIC reactor and
driving out the formed CO
2
via the NDIR detector.
The CO
2
or NO concentration is detected several times every second. An integral over
time is calculated from this signal sequence. The integral is proportional to the concen-
tration of the carbon or nitrogen in the measurement solution. Afterwards, the calcula-
tion of the carbon or nitrogen content in the sample is performed via a previously deter-
mined calibration function.
3.4
Measuring methods
The detection of several parameters can be combined in the multiWin control and anal-
ysis software.
3.4.1
TC analysis
TC: Total Carbon
In TC analysis, the total carbon contained in the sample, i.e. the organic and inorganic
bound carbon, as well as elemental carbon, is detected.
The sample is dosed automatically into the combustion tube and digested, and the gen-
erated carbon dioxide is detected.
TN
b
detection is possible in parallel to TC detection.
3.4.2
TOC analysis
TOC: Total Organic Carbon
In TOC analysis, the total organic bound carbon contained in the sample is detected.
TOC determination is carried out in the analyzer using the differential method which can
be described with the following formula.
TOC = TC – TIC
TOC - total organic carbon
TC - total carbon
TIC - total inorganic carbon
Two sequential measurements are used on one sample to determine TIC and TC. The
calculated difference is given as TOC. The differential method detects volatile as well as
non-volatile organic carbon compounds.
